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[email protected] themend@gmail.com is offline
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Default Restoring a Sherwood S-5000

Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket

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Default Restoring a Sherwood S-5000


Ok, pics coming soon...

First step was to take voltage measurements off the bias and HV+ rails. Here's what I got on my S-5000. By the way, there are two variants of the S-5000 that I will discuss later, basically the older, longer version and the newer, shorter version. The one I am working on here is one of the shorter types.

After the 20uf cap coming off the rectifier, there is a 33 ohm 7w resistor connecting to the next cap section, [email protected]. According to documentation, this point should measure 415v (plate) but I often find that it reads higher. This particular amp is currently measuring 438v on the plates! This is why you really have to have a 7189 here, or at least a beefy 6BQ5 that is known to handle high plate voltages. I've seen lesser Sovteks arc over in these amps before.

So, according to my Sams photofact, the correct voltages going down the HV+ rail are as follows on the left, and this amp is as follows on the right:

Photofact This S-5000

C1/A - 420v 442v
C1/B - 415v 438v
C1/C - 350v 365v
C2/A - 275v 285v
C2/B - 225v 204v

So right off the bat something looks amiss - All these voltages are a bit higher than listed, but that is ok. What is odd is that they're all higher except for one, which is quite a bit lower. That second section of C2 should be higher than 225v, since everything else is higher than listed. Instead, it's 21 volts lower than listed. I suspect this points to either that dropping resistor or that cap section being leaky. Either that, or current draw after that dropping resistor is higher than it's supposed to be for some reason. We'll have to get to the bottom of that.

Now on to the bias supply. It's interesting to note that the bias supply also supplies DC filament current to the two phono preamp tubes, which makes it even more interesting that I've never gotten a US made 12AX7 to sound good in those positions, getting hum regardless. I suppose it means that it was more induced hum from the surroundings than from the filaments as I had stated earlier, or perhaps there was something amiss in the amp in which I tried it. I will have to re-visit that whole thing once this is finished..

There are no real test points listed in the bias supply other than the final ouptut voltage, which is supposed to be -20v. This amp is currently putting out -21.8, which is probably right on target considering the plate voltage is running a tad high - the extra bias voltage is welcome. In fact, I'd like to see it a little higher, and once the selenium rectifier is swapped out for silicon diodes, I'll expect to see closer to -23v. A real indication of the health of this circuit will be the DC voltages at the phono tubes, since these actually have some current draw to them

Sam's Photofact This S-5000

C3/A - Unlisted -29.3v
C3/B - 24v 22.74v
C3/C - -20v -21.8v
V1 Fil - 24v 22.74
V2 Fil - 12v 11.06


So the bias supply looks good, but the DC voltages to the phono preamp section looks a tad soft. Who knows, filament starving can have nice effects, but It'll be interesting to see what happens when the selenium rectifier and those electrolytics are replaced. I always see the bias voltage increase, so the filament should as well. This SAM's photofact has the polarity of the bias cap backwards, FYI. I will post it all soon when I figure out where to put all the uploads for this project.


It should be noted that this amp currently works and sounds fantastic. No signs of hum, very clean sound, no issues at all except the power transformer gets a little bit hotter than I think it should be. Thermal gun measurements have gotten close to 136F. My experience tells me that the second rev. of the S-5000, which this one is, tend to run a little hotter due to smaller iron. However, I still feel this one is a bit hotter than it should be after two hours of running and I think a power supply rebuild might lower that figure by 10 degrees. Still, for a bone-stock amp built in 1959, this thing is nothing short of amazing.

More to come soon!


-forkinthesocket
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Default Restoring a Sherwood S-5000

Ok, so I guess I can just share the photos and schamtics via dropbox.

https://www.dropbox.com/sh/y4j5cv5ro8o5yja/cvW9ncqTtV#/

Here's what's in there so far:

Pictures of the various twistlock can caps that are there
A picture of the underbelly of the amp
A picture of the unbelievably wrong Sam's photofact of the bias supply
A picture of the -Actual- Sherwood schematic right from a manual, applying to this second rev of Sherwood S-5000
A picture of the selenium rectifier which will be replaced


Regarding the voltages I measured in my last post, it is good to note that Sherwood has different voltages listed in their schematic. However, the Sams schematic is referring to the first rev. of the S-5000, the 'longer chassis' model. These two models can easily be distinguished visually, by the way. The newer one has all the 12AX7s up front mounted flat and underneath a square tube cage with slotted vents and a tube placement sticker. The old version has the preamp tubes at a 45 degree angle, with individual tube shields.

So, let's re-do that chart against the Sherwood schematic since I think that will be more in line with reality in this particular amp. FYI, the Sams schematic has some SERIOUS errors in the bias section, mainly that the capacitors and diodes are in there backwards. Their version magically produces negative volts from positive diodes and caps. Sheesh. So that should never be used for anything.

Sherwood Schematic This S-5000

C53/A - unlisted 442v
C53/B - 425v 438v
C53/C - 350v 365v
C24/A - 270v 285v
C24/B - 250v 204v


That is very telling. We see that the plate voltage is much closer to being 'in-spec' than before, though it is still a tad high, I recall that always being the case in these amps. Nevertheless, we have even more of a problem now in the second section of C24, as we are now 46v shy of the listed value. This is looking even more like a real problem than it did before. Also note that Sherwood calls these two caps C53 and C24, where Sams calls them C1 & C2, which is probably a more logical choice. Nevertheless, from here on out I will refer to the Sherwood schematic. If somebody wants to discuss an older chassis, we can do that too...

I think that's all for today, though I might get around to replacing the selenium rectifier.


-forkinthesocket
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Default Restoring a Sherwood S-5000

Hello all,

Made some progress on the bias supply yesterday, but didn't get around to posting it. First, the selenium rectifier he
https://www.dropbox.com/s/27opjx5auy..._Rectifier.jpg

has been replaced with a pair diodes and a pair of caps mounted to a terminal strip as seen he
https://www.dropbox.com/s/bfynay796k...eplacement.jpg

There is nothing special about these diodes, they are rated for 1000v (total overkill) and 1.5 amps. Since silicone diodes tend to generate a bit of switching noise, two [email protected] mica caps have been added to shunt that noise to ground. While the center post of this terminal strip is mounted to the chassis, I find that using that mechanical connection as a ground can be hit and miss, so instead, I run a ground wire inside the chassis and solder it to the bottom of a cap can. Here is the diode bridge installed in the amp where the selenium rectifier once was:

https://www.dropbox.com/s/nzy9mw08cq..._installed.jpg

"But wait!", you say "Aren't you going to replace the capacitor cans?" Well, yes we are. But we are only going to replace the two HV+ capacitors, and while we will also replace the caps in the bias supply, we will not remove the old capacitor can. Why? Because it is a very rare capacitor can with COMMON POSITIVE. All other can caps are common negative, and you simply will not find a replacement for this bias supply can. So, we will have to rebuild the bias supply using axial and/or radial caps stuffed underneath the amp. Don't worry, there's room as we'll see later. For now solder the ground to an unused common terminal on the bias cap can as I did with the green wire he

https://www.dropbox.com/s/1knvs3qlc6...for_diodes.jpg

In order to mount the new diode bridge, I first had to cut 7/8" off the old mounting bolt for the selenium rectifier in order to use it. I just used the bolt cutter on my strippers. Check it out:

https://www.dropbox.com/s/eqwe6e7vgf..._off_screw.jpg

Ok, so I got all that done, now it's time to fire up the amp and take measurements. Oh crap! One of the output tubes is arcing over now! Better get the tester out!

After testing my output tubes, it turns out that it was a complete coincidence. One of the tubes had already had a part come loose inside, and all I had to do was operate the amp upside down to make the short happen. After testing, 3 tubes flunked the test. One arcs over, the other tests with shorts, and the last one is weak. Dang, and they're all Amperex Bugle Boys..... Anyway, after digging through my stash, I found a replacement for these three guys he

https://www.dropbox.com/s/y1suozb1di..._bad_tubes.jpg

Ok, now the amp fires up without any drama. As I expected before, my bias voltage has now risen up and is now -24.85v, about where I expect it to be with silicon diodes and no dropping resistor. Yes, you can get a couple more watts out of this thing with a lower bias, but the wear and tear on the output tubes and the heat generated makes it scarcely worth it, IMHO.

The DC filament voltages are now 26.1 and 12.7 volts at V2 and V1 respectively, up from 11.06 and 22.74. These might be just a touch high, but they're within the realm of sane. I may in fact try to put a slightly higher value dropping resistor in front of these.

I have also made some interesting observations regarding the voltages listed on the schematics, versus real life and I will get to that in my next post.
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Peter Wieck Peter Wieck is offline
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Default Restoring a Sherwood S-5000

On Sunday, January 12, 2014 5:11:25 PM UTC-5, hugeshows wrote:
Ok, pics coming soon...



First step was to take voltage measurements off the bias and HV+ rails. Here's what I got on my S-5000. By the way, there are two variants of the S-5000 that I will discuss later, basically the older, longer version and the newer, shorter version. The one I am working on here is one of the shorter types.

A few things out in the deep background he

a) Voltages at the wallplate: These days, with average household electrical use being anywhere between 50% and 200% greater than it was when that Sherwood was 'new', Utilities that have not significantly upgraded their final distribution systems (most) have increased the voltage in those systems. It is not uncommon for us to see up to 130V commonly at the wallplate at our house these days. And 5% over the 'nominal' 120V would account for most of your B+ variations.

Do you have access to a variac such that you might reduce the input voltage to 115V or so (much closer to what would have been the case in the 1960s throughout most of the US)?

b) Selenium diodes decay over time (and when they fail it can be quite spectacular and leave you gasping in amazement). As they decay their resistance increases.

My guess is that your selenium diodes are 'out' about 10% - so the higher line voltage overcomes some of that. NOTE and WARNING: if I am correct in that assumption, those diodes are closing in on the failure point. Get that block (or individual units) replaced ASAP.

I am not above installing the occasional dropping resistor in some of my equipment that was designed against a typical wallplate voltage of 110V or so - most 'stuff' made in the 1930s and 1940s. Post WW-II, nominal was about 115V, into the 1980s, mostly around 120V. And from about 2000, commonly well over that voltage. Filaments do not like voltage in excess of their rating. 5% high typically will translate to a 40% drop in life. AND, despite anecdotal and cult beliefs to the contrary, nor do they like low voltage very much either. Look up 'lazy cathode' and other phenomenon along those lines. Generally, there is nothing much wrong with 5% low. Beyond that and the consequences are worse than the benefits. Interesting aside - clearing 'lazy cathode' (AKA 'rejuvenation' in some circles) involves running filaments at a high voltage under controlled conditions. So be aware.

c) Drifted resistors - resistor technology has changed (mostly for the better) since the 1960s. These days, even 'cheap' resistors are typically well within 5% however they are marked. But older compositions often drifted - usually higher. It is always a good idea to check all the resistors.

Best of luck with this - it is a worthwhile endeavor.

Hum in the pre-amp: Given the extra amplification of the phono-stage, it will exaggerate any hum in the system that may not show up at from the line-level inputs. But, as it happens, most sources of hum in the phono section will be related to bad shielding, and/or a shield that is grounded at both ends (or the one end that should be connected is not). Start with the simple stuff such as physical damage or a failed connection. Then, look for the obvious - caps.

Never mind Andre - he is neither of consequence nor any particular use. Note also that the pictures (of himself) he allows are over 30 years old... There is far more ego than substance going on there.

Peter Wieck
Melrose Park, PA


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Default Restoring a Sherwood S-5000

On Sunday, January 12, 2014 2:52:54 PM UTC-5, wrote:
Hello all, One of my favorite tube amps has to be the Sherwood S-5000. ....

-forkinthesocket

Thank you for the weath of info! I happen to have an S-5000 that I love. It has a hum in the phono preamp though.. something I would like to get rid of. I really like how you can vary the loudness curve by adjusting the preamp volume along with the master volume, that plus the tone controls gives me plenty of ability to get the sound I want at any level. A very well thought out amp. The selector switch allows stereo, reverse stereo, mono channel A, mono B, & mono A+B plus, pulling out the balance knob changes the phase on one channel. Very flexible!
Here is a video of me testing it out when I first got it:
http://youtu.be/pRzVHkyYUso
It is now in my listening room connected to a set of vintage Warfedale speakers..

--JRC
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Default Restoring a Sherwood S-5000

Hi there!

Cool to see you here! I remember that video on YouTube! Man, what a fantastic rig you have behind it.

Looks like you have a later version of the S-5000 that I refer to as the short chassis, which is also the one I am working on here. From the video it looks like some work has been done on it already, notably the bias supply rectifier looks to have been replaced. We should also check the date codes on the capacitors to see what has and has not yet been done.

So far in this thread, I have measured the HV+ rail, and the bias+phono filament supply. Then, I replaced the selenium rectifier with an odd little arrangement of diodes and caps that I will explain later... Usually folks use one cap to hush the diode noise, I now use three; two at the diodes from their inputs to ground, and one on the bias voltage wire at the junction with the first electrolytic filter cap. That last one hasn't been added in my amp yet since that junction is going to be done along with the filter caps.

So, when you have a chance, check out those voltages (be careful, these are HIGH voltages) and post your results. Also, I am curious to see what make of tubes you have in your phono section, or for that matter the whole amp. From the top front of the amp, these will be the first two tubes, from left to right. They're directly behind the selector and balance knobs. If you're not sure what make they are, snap pictures of them. I am interested to see if they are Telefunken or not.

Good luck and let me know if you have any questions or issues. Oh, and welcome to RAT, by the way.

-forkinthesocket
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Default Restoring a Sherwood S-5000

While we wait to hear from JRC, let's go over the parts list for the rebuild.

First, let's talk about the large twistlock cap right behind the output tube section. This is the main filter capacitor for the HV+ supply, and it takes the brunt of the wear in the power supply. The reason for this is mainly because the capacitor is located in a spot which positively guarantees that it will get baked by the output tubes. Here is a picture of it:

https://www.dropbox.com/s/2lq2ltcke4gt11w/S-5000_C1.jpg

It's also peculiar in that it is mounted at an angle, just as the power tubes are, which is what gives this amplifier such a low height. There are a few schools of thought on twistlocks like these. Some people prefer to cut them open from the bottom, gut them, and stuff them with new radial or axial caps. The other notion is to simply put those same caps underneath the amp and re-wire everything to accommodate that. Some feel replacing the whole can is best when there are replacements available. Lastly, some people feel that they can magically 'reform' capacitors by doing some sort of rain dance with a variac. As you may have guessed, I do not fall into that last group of people.

While there probably are certain capacitors in certain amps that may respond to such a thing, this particular cap in this spot sees too much voltage and too much heat not to be somewhat degraded by now. Some of these S-5000s were never ran with the cover, since the cover was an additional cost; not included with the amplifier purchase. Lots of these were placed into consoles and the like and so did not build up all that much heat. These ones can often sound OK with the original cap. The S-5000 running inside its cover, especially a leatherette covered one will just cook away in there. These almost always have noticeable hum when played.

If we look underneath the cap he

https://www.dropbox.com/s/pefyhgh7l6...onnections.jpg

We see that there isn't a whole lot of room for adding caps underneath, without resorting to putting them in odd places, and adding new wires and terminal strips. So really, our best options are to either replace the can or stuff it with new caps. Since there are very good replacements available from CE, I suggest the extra money spend on this:

http://www.tubesandmore.com/products/C-EC4020X2-525

Is well worth it, especially considering the effort in re-stuffing a capacitor. Note that this capacitor is a 40/40/20/20 sectioned cap at 525v. The original Sherwood design called for a 20/40/40/5 sectioned cap at 500v for the first three sections, and 350 volts for the 5uf section. This CE cap is physically the same dimensions as the Sherwood cap, offers 25 more working volts, and gives us an extra 15uf on one section. As long as we are careful to wire the 20uf section to the 5AR4 rectifier, this cap is an ideal replacement.

Speaking of the 5AR4 and 20uf, there is a reason you must not increase the value of this particular cap. Tube rectifiers have a maximum capacitance that can be directly connected to the output. Those values are usually listed in tube manuals. If you add more here, the rectifier will likely arc over due to the current draw. After the first dropping resistor, you can literally add as much capacitance as you want, as the current rush will now be limited by that resistor. It is possible, however, to introduce a resonance by altering the R-C time constant by doing this. I have seen one S-5000 that wound up with a very low frequency power supply oscillation as a result of an odd re-cap, it showed up as very pronounced woofer excursion at around .5hz, which one might think would be beyond the capability of the output transformers, but obviously not.

So, in this case, everything will retain its original values except for the last section which will increase to 20uf from 5. I personally feel that 40uf is just adequate for the first section off the dropping resistor. Depending on how the terminals of this cap are laid out, I may decide to use the additional 20uf section to increase the first 40uf section to 60uf, and simply add a 10 or 20uf cap underneath for that last section. Since I have not used this particular cap before, I will have to wait until I have it on hand to see if the terminals and distances underneath will allow this. In the past, I have used Aero-M capacitors for this part, and was able to add capacitance easily.

For the second twistlock capacitor, I'm going to try this:

http://www.tubesandmore.com/products/C-EC20-20-450

Here's the original in the amp:

https://www.dropbox.com/s/kvxfs3grlzzpqfw/S-5000_C2.jpg

This is interesting - last time I did one of these S-5000s, there were no fresh stock 1" twistlocks available. Here we have a 20/20 @450v that is the same dimensions as the stock capacitor! The stock cap is a 20/30 @ 400, so we get a higher voltage rating with this cap, but come up 10uf short. However, there is plenty of room underneath next to this cap to add another 10uf or more. So, I'm going to order one of these to find out if they're suitable.

Lastly, we have the oddball bias supply capacitor. It has a common positive can, something that I rarely see anywhere else but on Sherwood amps. Anyone else know of amps that use these? I'm curious! As a side note, if you are ever working on a Sherwood and you see a twistlock capacitor can that is covered in cardboard, that can has high voltage on it and that cardboard is there as an insulator. Be careful with those!! Luckily, they don't exist on the s-5000 but you see them a lot in later Sherwood amps.

Anyway, the bias cap... It's a 250/150/50 @ 50v cap, and the best bet is to just leave it in place, and use axials or radials underneath to replace it. We don't need to go crazy here with capacitance, maybe a -little- more on the bias supply to lower ripple, but the vaules here seem pretty acceptable in practice.

So that's the update for now... I'm going to order the parts tomorrow and we'll see next week how they work out.


-forkinthesocket





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Andre Jute[_2_] Andre Jute[_2_] is offline
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Default Restoring a Sherwood S-5000

Yo, Dorkinthesocket, if you're such a newbie that you don't even have a junk box with a couple of IN4xxx in it, like a proper experimenter, as we see in your other self-important post, you really want to start in electronics with something less dangerous than tube voltages. -- Andre Jute

On Thursday, January 16, 2014 12:55:25 AM UTC, wrote:
While we wait to hear from JRC, let's go over the parts list for the rebuild.



First, let's talk about the large twistlock cap right behind the output tube section. This is the main filter capacitor for the HV+ supply, and it takes the brunt of the wear in the power supply. The reason for this is mainly because the capacitor is located in a spot which positively guarantees that it will get baked by the output tubes. Here is a picture of it:



https://www.dropbox.com/s/2lq2ltcke4gt11w/S-5000_C1.jpg



It's also peculiar in that it is mounted at an angle, just as the power tubes are, which is what gives this amplifier such a low height. There are a few schools of thought on twistlocks like these. Some people prefer to cut them open from the bottom, gut them, and stuff them with new radial or axial caps. The other notion is to simply put those same caps underneath the amp and re-wire everything to accommodate that. Some feel replacing the whole can is best when there are replacements available. Lastly, some people feel that they can magically 'reform' capacitors by doing some sort of rain dance with a variac. As you may have guessed, I do not fall into that last group of people.



While there probably are certain capacitors in certain amps that may respond to such a thing, this particular cap in this spot sees too much voltage and too much heat not to be somewhat degraded by now. Some of these S-5000s were never ran with the cover, since the cover was an additional cost; not included with the amplifier purchase. Lots of these were placed into consoles and the like and so did not build up all that much heat. These ones can often sound OK with the original cap. The S-5000 running inside its cover, especially a leatherette covered one will just cook away in there. These almost always have noticeable hum when played.



If we look underneath the cap he



https://www.dropbox.com/s/pefyhgh7l6...onnections.jpg



We see that there isn't a whole lot of room for adding caps underneath, without resorting to putting them in odd places, and adding new wires and terminal strips. So really, our best options are to either replace the can or stuff it with new caps. Since there are very good replacements available from CE, I suggest the extra money spend on this:



http://www.tubesandmore.com/products/C-EC4020X2-525



Is well worth it, especially considering the effort in re-stuffing a capacitor. Note that this capacitor is a 40/40/20/20 sectioned cap at 525v. The original Sherwood design called for a 20/40/40/5 sectioned cap at 500v for the first three sections, and 350 volts for the 5uf section. This CE cap is physically the same dimensions as the Sherwood cap, offers 25 more working volts, and gives us an extra 15uf on one section. As long as we are careful to wire the 20uf section to the 5AR4 rectifier, this cap is an ideal replacement.



Speaking of the 5AR4 and 20uf, there is a reason you must not increase the value of this particular cap. Tube rectifiers have a maximum capacitance that can be directly connected to the output. Those values are usually listed in tube manuals. If you add more here, the rectifier will likely arc over due to the current draw. After the first dropping resistor, you can literally add as much capacitance as you want, as the current rush will now be limited by that resistor. It is possible, however, to introduce a resonance by altering the R-C time constant by doing this. I have seen one S-5000 that wound up with a very low frequency power supply oscillation as a result of an odd re-cap, it showed up as very pronounced woofer excursion at around .5hz, which one might think would be beyond the capability of the output transformers, but obviously not.



So, in this case, everything will retain its original values except for the last section which will increase to 20uf from 5. I personally feel that 40uf is just adequate for the first section off the dropping resistor. Depending on how the terminals of this cap are laid out, I may decide to use the additional 20uf section to increase the first 40uf section to 60uf, and simply add a 10 or 20uf cap underneath for that last section. Since I have not used this particular cap before, I will have to wait until I have it on hand to see if the terminals and distances underneath will allow this. In the past, I have used Aero-M capacitors for this part, and was able to add capacitance easily.



For the second twistlock capacitor, I'm going to try this:



http://www.tubesandmore.com/products/C-EC20-20-450



Here's the original in the amp:



https://www.dropbox.com/s/kvxfs3grlzzpqfw/S-5000_C2.jpg



This is interesting - last time I did one of these S-5000s, there were no fresh stock 1" twistlocks available. Here we have a 20/20 @450v that is the same dimensions as the stock capacitor! The stock cap is a 20/30 @ 400, so we get a higher voltage rating with this cap, but come up 10uf short. However, there is plenty of room underneath next to this cap to add another 10uf or more. So, I'm going to order one of these to find out if they're suitable.



Lastly, we have the oddball bias supply capacitor. It has a common positive can, something that I rarely see anywhere else but on Sherwood amps. Anyone else know of amps that use these? I'm curious! As a side note, if you are ever working on a Sherwood and you see a twistlock capacitor can that is covered in cardboard, that can has high voltage on it and that cardboard is there as an insulator. Be careful with those!! Luckily, they don't exist on the s-5000 but you see them a lot in later Sherwood amps.



Anyway, the bias cap... It's a 250/150/50 @ 50v cap, and the best bet is to just leave it in place, and use axials or radials underneath to replace it. We don't need to go crazy here with capacitance, maybe a -little- more on the bias supply to lower ripple, but the vaules here seem pretty acceptable in practice.



So that's the update for now... I'm going to order the parts tomorrow and we'll see next week how they work out.





-forkinthesocket

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Default Restoring a Sherwood S-5000

ha.. wow.
Hey forkinthesocket..
I finally got my Sherwood, multimeter and a glass of SOCO in the same room... and my wife and kid in another room! Gonna be taking those measurements in the next hour or so. Will reply back tonight. so in the mean time, quit ****in on Andre's blarney stone and go write some more poetry...
whatever..
I greatly appreciate you sharing your knowledge on this particular amplifier!
it's just the kick in the ass I need to get mine working up to snuff.

--JRC


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Default Restoring a Sherwood S-5000

Hey, cool I'm looking forward to it. Please upload some pics if you can, if you need a place to put them, PM me and I'll share my dropbox folder with you.

Cheers,

-forkinthesocket


On Saturday, January 18, 2014 8:25:17 PM UTC-5, wrote:
ha.. wow.

Hey forkinthesocket..

I finally got my Sherwood, multimeter and a glass of SOCO in the same room.. and my wife and kid in another room! Gonna be taking those measurements in the next hour or so. Will reply back tonight. so in the mean time, quit ****in on Andre's blarney stone and go write some more poetry...

whatever..

I greatly appreciate you sharing your knowledge on this particular amplifier!

it's just the kick in the ass I need to get mine working up to snuff.



--JRC


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Default Restoring a Sherwood S-5000

OK, here are the stats. The main filter cap has been replaced with another can. Others have been replaced underneath.
Link to pics: https://www.dropbox.com/sh/zoqcrtzbmn1saha/JxXYbkaIIc

C1/a 472VDC
C1/b 470VDC
C1/c 388VDC
C2/a 301VDC
C2/b 217VDC
A lot higher than what you had, and what specs show! No wonder the 6BQ5's I originally tried for power amps were arcing.

There is an additional cap (see it in the C1 photo, to the right of the can) that has 46VDC on it.

Bias caps; These have been replaced, so my measurements are left to right as viewed in the pic:
-26.6vdc, -34.5vdc, -26.1vdc

As for the DC filiment voltages, the only one I found was 13.3VDC on the first two 12AX7's where is the 24V supposed to be?

Selineium rectumfryers have been replaced with diodes, see pic.

Tubes are as follows from the top, Left to right nearest the front: three Telefunken 12ax7, two Tesla ecc803s. Adjacent the filter cap are two RCA 7199.

I will note that the phono hum seemed to be less on my workbench than in the workshop that I am using the amp, not sure if that is because of smaller speakers, or lack of 8-ft flourescent lights above, or just power situations. But, it is still there. The amp is quite silent on FM input (used for my iPod)

--JRC


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Default Restoring a Sherwood S-5000

Good god, those voltages are HIGH! Quick question - did you per chance take those measurements with the power tubes removed? That would explain why they are so high. If so, please take the measurements again with the power tubes installed. If not, what is your AC line voltage? Can you measure the AC HV coming off the transformer?


Thanks,

-forkinthesocket

On Saturday, January 18, 2014 9:53:18 PM UTC-5, wrote:
OK, here are the stats. The main filter cap has been replaced with another can. Others have been replaced underneath.

Link to pics: https://www.dropbox.com/sh/zoqcrtzbmn1saha/JxXYbkaIIc



C1/a 472VDC

C1/b 470VDC

C1/c 388VDC

C2/a 301VDC

C2/b 217VDC

A lot higher than what you had, and what specs show! No wonder the 6BQ5's I originally tried for power amps were arcing.



There is an additional cap (see it in the C1 photo, to the right of the can) that has 46VDC on it.



Bias caps; These have been replaced, so my measurements are left to right as viewed in the pic:

-26.6vdc, -34.5vdc, -26.1vdc



As for the DC filiment voltages, the only one I found was 13.3VDC on the first two 12AX7's where is the 24V supposed to be?



Selineium rectumfryers have been replaced with diodes, see pic.



Tubes are as follows from the top, Left to right nearest the front: three Telefunken 12ax7, two Tesla ecc803s. Adjacent the filter cap are two RCA 7199.



I will note that the phono hum seemed to be less on my workbench than in the workshop that I am using the amp, not sure if that is because of smaller speakers, or lack of 8-ft flourescent lights above, or just power situations. But, it is still there. The amp is quite silent on FM input (used for my iPod)



--JRC


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Default Restoring a Sherwood S-5000

On Sunday, January 19, 2014 2:07:28 PM UTC-5, hugeshows wrote:
Good god, those voltages are HIGH!


yea, that's what I thought.. I did measure my AC line, but don't remember the exact voltage, but it was not out of the norm.

No tubes were removed, the amp was at idle with about 10 minutes warm-up time.
I'll take a look at the AC HV tonight.

Oh, and I don't suppose there is a line voltage selection of any time is there? If it was tapped for 110VAC that might explain it. I get something close to 120-125 VAC here.

I have a variac, and so I will put it inline and see what it takes to get them lower. I guess I should look at AC filament voltages too?

--John
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Default Restoring a Sherwood S-5000

errata from last post:

1) When orienting the cap as I described, it is not only important to align a 20uf section with the rectifier, it is also important to align the two 40uf sections with their original locations! So, the new cap has two 20uf sections, meaning there are two ways you can orient it and have a 20uf section for the rectifier. One of them will give you the two 40uf sections where you want and one way won't. Starting with the section to the right of the missing ground tab, and going counter-clockwise, orient the new cap so that you start with 20, then 40, and 40, then 20, again starting with the rectifier's section and going counter-clockwise. The other way is 20,20,40,40 and that isn't what you want.

2) I mentioned that the new cap was 500v, but it is actuall 525v as I had said in earlier posts.


-forkinthesocket


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Default Restoring a Sherwood S-5000

Hello all,


So I am finally getting around to writing up the place where I decided to call it quits, electrically speaking. Generally, I find the coupling caps to be good in the S-5000, and so when there are no indications of problems, I leave them alone. I think to do otherwise changes the character of the amp, and that is not something that I either encourage or discourage, because it's a personal choice. However, I think that for my tastes, once the power supply is up to snuff and everything checks out electrically and the amp sounds good, that's when I usually stop.

First off, the power supply rebuild... As you know, I went with the reproduction twistlocks from CE, which I purchased from AES. These capacitors seem to be of high quality, though I did have issues with the 1" diameter can and had to get a replacement. Regrettably, even the second one was a bit out of round at the base as if the crimping machine were having issues with that size, or the die was out of round. Anyway, I decided to install it and it worked out fine. There was nothing remarkable about this cap except that it was a 20/20 cap and the stock was a 30/20. So I added a 10uf cap in parallel to the underside and wound up with over 35uf measured for that section.

The bias supply is what turned out to be the most challenging, since it is sort of an odd circuit, the way its positive side is floated from the chassis. The main issue is that I decided to rebuild the voltage dropping resistors using the stock parts and obviously values as well. The result of this is that the increased voltage from the silicon diodes in the bias circuit along with resistor values that were derived for a selenium rectifier caused an elevated bias voltage which made the output tubes run rather cold. Keep in mind that the bias adjustment pots on this amplifier merely adjust the balance of bias voltage on each channel, they do not control overall voltage and there is no way to match each tube's current draw across channels.

After rebuilding the circuit with the stock resistors and new capacitors (underneath) I started taking measurements. I was seeing that the output tubes were drawing less than 15ma plate current at idle, and that's cold for any 7189 amp even at 440v plate. Bias voltage was in the 24v range, and the DC filament supply for the phono section was at about 26.5. Clearly, the stock circuit could not supply the right voltages with a silicon rectifier. Rather than attempting to re-engineer the bias and DC filament circuits just now, I decided to experiment with putting different value resistors in series between the diodes and the first capacitor, and I arrived with an interesting solution.

https://www.dropbox.com/s/gzmtpckjoy...ias_Supply.jpg

Keep in mind that those two green ground connections were later deleted in regards to the mistakes I mentioned in my last post. Anyway, as you can see, I've taken a very old Ohmite 10w wirewound resistor of the screw-mount type and mounted it inside the chassis, bypassed by a 40 ohm 2w precision resistor that Stephie sent me many years back. The resulting parallel resistance is 8 ohms, and that turns out to put the voltages right where I want them.

Why chose two resistors instead of one? Well, I wanted to be able to adjust the bias voltage a bit. I found that 10 ohms ran it just about as hot as I'd ever want the tubes to run, around 24ma a piece with some tubes! 8 ohms got my used Amperex 7189s to run at 21ma a piece, which is about where these Sherwoods run stock. Yes, that's a LOT for this type of tube, which is why you have to stick with ones that can handle the higher plate voltage. Anyway, the 40 ohm resistor can be removed by me at any point if I want to run things a but hotter, or have tubes that need a little less bias to get their current up. If I find a 2w rheostat to replace it with that I can mount internally without drilling, then I might use that as the shunt. Basically, by using a big overrated resistor like that 10w, I guarantee that my bias voltage won't fail due to a crappy pot. If I put a rheostat where that 40 ohm resistor is now and it faults open, the bias circuit fails hot, but safe because the 10 ohm resistor is in parallel.

So, with this arrangement I wind up with 23.6 volts at the top of the DC filament supply, and around 19v bias finally making it to the tubes after the balance pots. This gives me around 19-21 ma idle current per tube at 440v plate.

So, I've also modified that cathode resistors, and done something new - I reused the AC accessory sockets for bias measurement points, and it works brilliantly! You can either measure each tube individually, or measure the balance of a pair by connecting the meter to both points. Since the S-5000 is setup with a balance type bias circuit, this works out great and can be used in place of or along with the hum balance test described in the manual.. FYI- Hum balance in the S-5000 is not the classic hum balance circuit you find in other amps, it's really a fixed bias balance adjustment using injected and then cancelled hum to determine the center point.

So the bias has been left stock, except there is now 8 ohms between the diodes and the rest of the circuit. The dual 12 ohm 1w cathode resistors have now been replaced with 4 individual 1w precision 10 ohm resistors. From the cathodes, I ran a 4 conductor solid core ribbon wire over to the AC sockets which were reclaimed in the AC supply rebuild (more on that later). Here's how I did it:

https://www.dropbox.com/s/o20s9dxgon...sistor_Mod.jpg

The ribbon cable simply goes down between the output tubes, where it ties to each cathode. From there, it runs under the lip of the chassis towards the sockets. Just before the sockets, there's a screw hole. At that spot, I carefully bent a dip in the cable (solid core) and wrapped it with a bit of friction tape to protect it from future screws. And then each channel's pair was soldered to a socket, I laid it out logically.

Now I can measure each tube's bias, correlate "hum balance" to real-world figures, and see just how hot I'm running things without even opening the chassis. If you measure from each terminal to chassis, you see a number which is converted into ma with no math at all, save moving a decimal twice.

https://www.dropbox.com/s/jic4damuuo..._terminals.jpg

Here is the AC power input and the bias measurement points again. This is after I restored the stock chassis-line capacitor arrangement, but now that I had re-purposed the AC receptacles that the cap was mounted to, I had to add a terminal strip to the bolt on the transformer. From there, I re-wired the power supply to put the hot leg of the AC through first the fuse, then the power switch, then the transformer primary. Jumpers were made to connect hot to the new terminal strip and the cap, where neutral and the other primary leg was connected. The cap was grounded to the chassis at that spot, which seems to have the same hum level as its old position so far, fairly low.

I must say that I find having bias measuring points far more useful than an accessory outlet that dirties the noise floor when used, and despite a nostalgia for keeping things stock, this modification works well for me.

I'm getting sleepy, so that's all for now.


Cheers,

-forkinthesocket
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Default Restoring a Sherwood S-5000

I have an opportunity to buy an S 5000 in beautiful shape. Would you be kind enough to call me to discuss restoring it.
Bill
630 745 8261
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"C24/B - 250v 204v"

Hi, did you figure out why you measured 46v below what the schematic reads?

Sorry if I missed the explanation but I only see how you resolved the bias voltage supply.

Cheers!
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Default Restoring a Sherwood S-5000

On Wednesday, July 23, 2014 11:49:00 PM UTC-4, wrote:
"C24/B - 250v 204v"



Hi, did you figure out why you measured 46v below what the schematic reads?



Sorry if I missed the explanation but I only see how you resolved the bias voltage supply.



Cheers!


Sorry folks, haven't checked in here in a while. I'll take another look this weekend and see if I can answer some of these questions.

Cheers!
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Default Restoring a Sherwood S-5000

I notice things have died down a bit.

Anyway, I looked and foud that the S-5000 used the Williaamsin configuration but the S-5000A did not. I had an S-5000A for a while. Damn thing got disconnected from one speaker at some point and had an arced over tube socket. Not happy.

But you got the real McCoy I guess.

So, do anything lately on it ?


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On Sunday, October 26, 2014 5:49:24 PM UTC-4, wrote:
I notice things have died down a bit.

Anyway, I looked and foud that the S-5000 used the Williaamsin configuration but the S-5000A did not. I had an S-5000A for a while. Damn thing got disconnected from one speaker at some point and had an arced over tube socket. Not happy.

But you got the real McCoy I guess.

So, do anything lately on it ?


A bit, actually. Of late I've been on audioasylum more than here, but I certainly don't mind coming to some sort of conclusion with this thread, and I realize there is more work to do. I recently acquired an S-360, a rare monoblock Sherwood meant to turn the S-4400 unit into a complete stereo amp/preamp, and I will be diving into that soon.

Are there any particular questions still outstanding that you had?


Cheers.
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Default Restoring a Sherwood S-5000

It's really just curiousity.
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Default Restoring a Sherwood S-5000

On Friday, October 10, 2014 at 3:02:00 PM UTC-5, hugeshows wrote:
On Wednesday, July 23, 2014 11:49:00 PM UTC-4, wrote:
"C24/B - 250v 204v"



Hi, did you figure out why you measured 46v below what the schematic reads?



Sorry if I missed the explanation but I only see how you resolved the bias voltage supply.



Cheers!


Sorry folks, haven't checked in here in a while. I'll take another look this weekend and see if I can answer some of these questions.

Cheers!



Hello. This is a great write up on the 5000. I just picked up one of these on Eaby. Its the S-5000 20 + 20 Stereo Amplifier. Its the unit that has the 4 pushbuttons on the left front panel for phone manipulation. The tube compliments are 5 Sovtek 12AX7(1208), 2 RCA 7199, I cant make out what the output tubes are as the ink has been worn off but what is left of the lettering is 6BQ5 and 065-090 and the word organ. I would like to know if I should replace the phone tubes(the two at the far left) with something else, I primarily listen to the phone input. Also would I benefit from different 7199's or output tubes. Much thanks for your advise.
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Default Restoring a Sherwood S-5000

Just wondering if these can be used as preamplifiers? Do they have a preamp out? Specifically the s5000ii. Thanks
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Default PWR transformer for a Sherwood S-5000

On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket


New guy. Desperate for help.
The post about restoring the Sherwood S-5000 caught my eye.
I sure would like to do that, but....
My poor amp has a blown power transformer.
Any ideas on a replacement?


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Default PWR transformer for a Sherwood S-5000

On Sunday, August 2, 2015 at 2:33:49 PM UTC-4, wrote:

New guy. Desperate for help.
The post about restoring the Sherwood S-5000 caught my eye.
I sure would like to do that, but....
My poor amp has a blown power transformer.
Any ideas on a replacement?


It would be helpful to know the make/model/condition of your amp. And what specific part of the PT that is blown, if known. For instance, if the primary winding is bad, then it is pretty much hopeless, as with the B+ winding(s). But if it is a filament winding (6.3V or 5V) you may be able to install a separate filament transformer.

If you have any of several Dynaco products, OEM replacements are still being made, less so for other brands, but still out there.

And, of course, are the usual transformer builders such as Hammond and others that have both a range of replacement transformers and will even make one for you at a reasonable price, especially if it is already templated.

Lastly, there are transformer rewinders out there that do a fairly credible job with units that may not be otherwise available. Just look up "Transformer Rewinding Service" and take your pick.

Best of luck with it.

Peter Wieck
Melrose Park, PA
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Default PWR transformer for a Sherwood S-5000

On 08/02/15 11:33, so wittily quipped:
On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket


New guy. Desperate for help.
The post about restoring the Sherwood S-5000 caught my eye.
I sure would like to do that, but....
My poor amp has a blown power transformer.
Any ideas on a replacement?


maybe search on Mouser's web site for a Hammond equivalent. They have a
*LOT* of tube transformers there, power supplies, output, impedence
matching, etc.. It's worth a shot. if you know the correct voltage,
amperage, physical size, etc. you might just get an equivalent that has
extra windings or whatever but still does the job.


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Default Restoring a Sherwood S-5000

On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket


Yea, I did miss a few details, I guess. I wanted to see if I could work the system before I dove in.
I had read several posts about how good the Sherwood S-5000 is so I bought my own. Nice cosmetic condition but a blown PWR transformer. Primary side..

Main problem with getting a non-stock replacement is the tight fit and the 30VDC filament and bias voltage needed.
The numbers on the transformer are B922J3-5 and A949005.
If I can't find an original replacement, I will have to look at the rewinding option. Seem that would be a bit costly. I'm in no hurry, so I will wait a while.
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Default Restoring a Sherwood S-5000

On Wednesday, August 5, 2015 at 5:26:31 PM UTC-4, wrote:
On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket


Yea, I did miss a few details, I guess. I wanted to see if I could work the system before I dove in.
I had read several posts about how good the Sherwood S-5000 is so I bought my own. Nice cosmetic condition but a blown PWR transformer. Primary side.

Main problem with getting a non-stock replacement is the tight fit and the 30VDC filament and bias voltage needed.
The numbers on the transformer are B922J3-5 and A949005.
If I can't find an original replacement, I will have to look at the rewinding option. Seem that would be a bit costly. I'm in no hurry, so I will wait a while.


You can check out these guys-

http://www.heyboertransformers.com/tubeamps.shtml

They made a custom power transformer for my LK72 Scott several years ago at a very reasonable price. They may know what specs you need already or you'll have to draw up a spec.

BR's,

Mark
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Big Bad Bob Big Bad Bob is offline
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Default Restoring a Sherwood S-5000

On 08/07/15 16:29, MarkS so wittily quipped:
On Wednesday, August 5, 2015 at 5:26:31 PM UTC-4, wrote:
On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket


Yea, I did miss a few details, I guess. I wanted to see if I could work the system before I dove in.
I had read several posts about how good the Sherwood S-5000 is so I bought my own. Nice cosmetic condition but a blown PWR transformer. Primary side.

Main problem with getting a non-stock replacement is the tight fit and the 30VDC filament and bias voltage needed.
The numbers on the transformer are B922J3-5 and A949005.
If I can't find an original replacement, I will have to look at the rewinding option. Seem that would be a bit costly. I'm in no hurry, so I will wait a while.


You can check out these guys-

http://www.heyboertransformers.com/tubeamps.shtml

They made a custom power transformer for my LK72 Scott several years ago at a very reasonable price. They may know what specs you need already or you'll have to draw up a spec.

BR's,

Mark


interesting, I'll bookmark that too. Wish I'd known about that before
tossing old gear [because of bad transformers, thinking there was no
hope, but that was decades ago]




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[email protected] bhamham@gmail.com is offline
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Default Restoring a Sherwood S-5000

Hi everyone,

My first post here. I've only briefly skimmed this thread but it sure looks to be a great resource for restoring the Sherwood S-5000. I've got one on the bench - the older version with the separate tube shields on the 12AX7s. I'm not getting any sound at all.

I've checked all the voltages on the schematic and found that V3 for both grids is way off. Should be -1V on one side and -1.5V on the other. I've got around 18v for each. I've checked all the resistors attached to V3 and they're OK. I haven't checked any caps, thought I'd seek advice before I start lifting leads.

My supply voltages all appear to be OK. There's 415v on the 7189 plates (using those Soviet EL84s), Bias is -16 but it still has the selenium rectifier and old caps. Someone changed out the 3-way power can but that's all that's been done. I've checked all the tubes and swapped out V3 with a known good one.

I'm still learning to troubleshoot tube gear and hoping to learn a good deal with this Sherwood. Any help would be really appreciated.

Regards,
Bruce

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[email protected] ad4kruit@msn.com is offline
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Default Restoring a Sherwood S-5000

On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket


I just checked. It would be $120 plus shipping? Not too bad.
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[email protected] clittle@kumc.edu is offline
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Default Restoring a Sherwood S-5000

Dear All,

I am seeking practical advice, further I am not a knowledgeable electronics guy, tube or otherwise -- to say the least.

A few years ago I was fortunate enough to find and purchase a Sherwood S5000 II; I am into 50s cars and hot rods and just wanted the aesthetics and joy of tube hi-fi ownership. A Sherwood expert here in the KC area completely refurbished the unit with no shortcuts taken. He only charged me for parts, not labor. Until recently my 5000S has provided excellent service for about two years of moderate use.

A couple of months ago the amp began generating some sort of signal spike that resulted in conspicuously loud crackling noise through the speakers. Since I do not use the amp's metal dust cover I was able to observe bright light flashes emitting from one of the four identical "power" (??) vacuum tubes situated at the rear of the amp.

I pulled out the offending vacuum tube, which unlike its counterparts showed discoloration at the "top" of the glass, presumably plasma vapor deposited metal.

The tubes, I now know, are Russian built electro-harmonic 7591A units. I was unable to contact the fellow who refurbished the S5000 II, so I went online and found multiple vendors for the Russian 7591A tubes. I bought a "set" of four, which I received and which appear identical to the my "original" electro-harmonic tubes.

Now my reason for this query: The cross-sectional diameter of the electro-harmonic 7591A units are too large to fit properly in the Sherwood sockets. What gives?

A brief search online suggests to this novice that these modern aftermarket tubes are (duh) fatter than the original electron tubes. I see mention of aftermarket pin adapters so that tubes with similar electronic properties, but different pin patterns, can be substituted. Does such an adapter exist for my Sherwood sockets?

Alternatively, because the shape of the electro-harmonic 7591A glass housings are slightly tapered cones (thinner toward the top) if one had a half-inch tall adapter 7591-to-7591 the Russian tubes would then fit without side-to-side glass contact, assuming I alternated adapters at every other socket position. Does such an adapter exist?

As it stands right now the four "new" tubes contact their respective neighbor, with the outermost (2) tubes unable to fit squarely into their socket. Am I correct in thinking that such glass-to-glass contact is not good for electron tube lifetime? This mechanical interference has to be putting stress on the glass, right? Should I pay big bucks for NOS tubes that fit properly?

Any advise or suggestions will be sincerely appreciated. I guess it's not the end of the world if I have to replace tubes often, but the present arrangement seems pretty lame to me.

Thanks,

Charlie
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MarkS[_3_] MarkS[_3_] is offline
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Default Restoring a Sherwood S-5000

On Sunday, September 6, 2015 at 3:00:42 PM UTC-4, wrote:
Dear All,

I am seeking practical advice, further I am not a knowledgeable electronics guy, tube or otherwise -- to say the least.

A few years ago I was fortunate enough to find and purchase a Sherwood S5000 II; I am into 50s cars and hot rods and just wanted the aesthetics and joy of tube hi-fi ownership. A Sherwood expert here in the KC area completely refurbished the unit with no shortcuts taken. He only charged me for parts, not labor. Until recently my 5000S has provided excellent service for about two years of moderate use.

A couple of months ago the amp began generating some sort of signal spike that resulted in conspicuously loud crackling noise through the speakers. Since I do not use the amp's metal dust cover I was able to observe bright light flashes emitting from one of the four identical "power" (??) vacuum tubes situated at the rear of the amp.

I pulled out the offending vacuum tube, which unlike its counterparts showed discoloration at the "top" of the glass, presumably plasma vapor deposited metal.

The tubes, I now know, are Russian built electro-harmonic 7591A units. I was unable to contact the fellow who refurbished the S5000 II, so I went online and found multiple vendors for the Russian 7591A tubes. I bought a "set" of four, which I received and which appear identical to the my "original" electro-harmonic tubes.

Now my reason for this query: The cross-sectional diameter of the electro-harmonic 7591A units are too large to fit properly in the Sherwood sockets.. What gives?

A brief search online suggests to this novice that these modern aftermarket tubes are (duh) fatter than the original electron tubes. I see mention of aftermarket pin adapters so that tubes with similar electronic properties, but different pin patterns, can be substituted. Does such an adapter exist for my Sherwood sockets?

Alternatively, because the shape of the electro-harmonic 7591A glass housings are slightly tapered cones (thinner toward the top) if one had a half-inch tall adapter 7591-to-7591 the Russian tubes would then fit without side-to-side glass contact, assuming I alternated adapters at every other socket position. Does such an adapter exist?

As it stands right now the four "new" tubes contact their respective neighbor, with the outermost (2) tubes unable to fit squarely into their socket.. Am I correct in thinking that such glass-to-glass contact is not good for electron tube lifetime? This mechanical interference has to be putting stress on the glass, right? Should I pay big bucks for NOS tubes that fit properly?

Any advise or suggestions will be sincerely appreciated. I guess it's not the end of the world if I have to replace tubes often, but the present arrangement seems pretty lame to me.

Thanks,

Charlie


Hi Charlie,

Glass to glass contact is not great idea. Beyond NOS 7591A's, there are other options. Right up front, I do not have any personal experience with the new production 7591A's, just NOS- but these days, that can be a crap shoot as well. Anyway, JJ makes a 7591A that is the same diameter as NOS so they should fit better. Also, the same company that makes the Electro Harmonix 7591A's (New Sensor) also released a so called "re-issue" Tung Sol 7591A. I believe these are the same diameter as the JJ / NOS but appear to be 2x the price of JJ's. If I were going to new production, I would probably go with the Tung Sols.
The spacer idea is neat but you may have to make those yourself. Use a tube socket and tube base. There was a time when the 6GM5 was an NOS 7591A alternative but had a different base so an adapter was needed. The price of a 6GM5 is up there now an NOS 7591A anyway so the climb might not be worth the view.

BR's,

Mark
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[email protected] clittle@kumc.edu is offline
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Default Restoring a Sherwood S-5000

On Monday, September 7, 2015 at 7:45:24 AM UTC-5, MarkS wrote:
On Sunday, September 6, 2015 at 3:00:42 PM UTC-4, wrote:
Dear All,

I am seeking practical advice, further I am not a knowledgeable electronics guy, tube or otherwise -- to say the least.

A few years ago I was fortunate enough to find and purchase a Sherwood S5000 II; I am into 50s cars and hot rods and just wanted the aesthetics and joy of tube hi-fi ownership. A Sherwood expert here in the KC area completely refurbished the unit with no shortcuts taken. He only charged me for parts, not labor. Until recently my 5000S has provided excellent service for about two years of moderate use.

A couple of months ago the amp began generating some sort of signal spike that resulted in conspicuously loud crackling noise through the speakers.. Since I do not use the amp's metal dust cover I was able to observe bright light flashes emitting from one of the four identical "power" (??) vacuum tubes situated at the rear of the amp.

I pulled out the offending vacuum tube, which unlike its counterparts showed discoloration at the "top" of the glass, presumably plasma vapor deposited metal.

The tubes, I now know, are Russian built electro-harmonic 7591A units. I was unable to contact the fellow who refurbished the S5000 II, so I went online and found multiple vendors for the Russian 7591A tubes. I bought a "set" of four, which I received and which appear identical to the my "original" electro-harmonic tubes.

Now my reason for this query: The cross-sectional diameter of the electro-harmonic 7591A units are too large to fit properly in the Sherwood sockets. What gives?

A brief search online suggests to this novice that these modern aftermarket tubes are (duh) fatter than the original electron tubes. I see mention of aftermarket pin adapters so that tubes with similar electronic properties, but different pin patterns, can be substituted. Does such an adapter exist for my Sherwood sockets?

Alternatively, because the shape of the electro-harmonic 7591A glass housings are slightly tapered cones (thinner toward the top) if one had a half-inch tall adapter 7591-to-7591 the Russian tubes would then fit without side-to-side glass contact, assuming I alternated adapters at every other socket position. Does such an adapter exist?

As it stands right now the four "new" tubes contact their respective neighbor, with the outermost (2) tubes unable to fit squarely into their socket. Am I correct in thinking that such glass-to-glass contact is not good for electron tube lifetime? This mechanical interference has to be putting stress on the glass, right? Should I pay big bucks for NOS tubes that fit properly?

Any advise or suggestions will be sincerely appreciated. I guess it's not the end of the world if I have to replace tubes often, but the present arrangement seems pretty lame to me.

Thanks,

Charlie


Hi Charlie,

Glass to glass contact is not great idea. Beyond NOS 7591A's, there are other options. Right up front, I do not have any personal experience with the new production 7591A's, just NOS- but these days, that can be a crap shoot as well. Anyway, JJ makes a 7591A that is the same diameter as NOS so they should fit better. Also, the same company that makes the Electro Harmonix 7591A's (New Sensor) also released a so called "re-issue" Tung Sol 7591A. I believe these are the same diameter as the JJ / NOS but appear to be 2x the price of JJ's. If I were going to new production, I would probably go with the Tung Sols.
The spacer idea is neat but you may have to make those yourself. Use a tube socket and tube base. There was a time when the 6GM5 was an NOS 7591A alternative but had a different base so an adapter was needed. The price of a 6GM5 is up there now an NOS 7591A anyway so the climb might not be worth the view.

BR's,

Mark


THANKS MARK

Just the focused spot-on information I needed. If you ever need any info old hot rods give me a holler.

Charlie


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Default Restoring a Sherwood S-5000

I have an RCA S-5000 which looks very similar to your picture. Didn't open it up yet but is it the same?
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Default Restoring a Sherwood S-5000

On Sunday, January 12, 2014 at 12:52:54 PM UTC-7, hugeshows wrote:
Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket


Would you consider doing a restoration to my S 5000 ? Please call me at 406-461-8700
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Default Restoring a Sherwood S-5000

On Saturday, August 1, 2020 at 11:38:25 AM UTC-5, wrote:
On Sunday, January 12, 2014 at 12:52:54 PM UTC-7, hugeshows wrote:
Hello all,

One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.

The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.

The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.

In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.

If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.

Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.

For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.

This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.

Feel free to ask away as I prepare some pics and schematics to get this started.


-forkinthesocket

Would you consider doing a restoration to my S 5000 ? Please call me at 406-461-8700

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