[Casper[_4_]]

Hi all!

I have a concern regarding fuses in my Adcom GSA-560 amp. The orginal
fuses blew and I was out of backups. I went to Rat Shack but they did
not have any more in that size except for slo-blo. I searched the
internet for them and came up empty handed. So, I contacted Adcom, who
sent me fuses, but they are slo-blo. Adcom's original manual states
not to use slo-blo on this unit. So being cautious, I called Adcom and
the person (non-tech) I spoke with assured me the technicians say
using slo-blo is fine. I'm still not certain if I should use the new
fuses. Any input on this? Am I just being overly cautious? Or should I
be wary of slo-blo causing more damage to my unit?

Thanks!
`Casper

[[email protected]]

On Jul 24, 9:26 pm, Casper wrote:
Hi all!

I have a concern regarding fuses in my Adcom GSA-560 amp. The orginal
fuses blew and I was out of backups. I went to Rat Shack but they did
not have any more in that size except for slo-blo. I searched the
internet for them and came up empty handed. So, I contacted Adcom, who
sent me fuses, but they are slo-blo. Adcom's original manual states
not to use slo-blo on this unit. So being cautious, I called Adcom and
the person (non-tech) I spoke with assured me the technicians say
using slo-blo is fine. I'm still not certain if I should use the new
fuses. Any input on this? Am I just being overly cautious? Or should I
be wary of slo-blo causing more damage to my unit?

YOu have a couple of issues: let's settle each in turn.

First, who do you think is going to give you better
advice on the detailed technical workings of your
Adcom amplifier: the technical department of Adcom,
or members of a general forum on audio? If your
answer is members of the forum, how might you deal
with answers that contradict one another?

If it were my amplifier, I'd be far more inclined to trust the
advice of the manufacturer than some otherwise unknown
collection of advice from the web, but that's satisfying my
criteria.

If you want, get a statement in writing from the
manufacturer stating their recommendation is to use
the slo-blo fuses and, if your amp blows up, you have
a legal leg to stand on if it can be shown the amplifier
failed as a direct consequence of using the wrong
fuse.

The second point is putely technical and has a couple
of parts to it.

Part 2a is to determine exactly why the fuses blew to
begin with. A blown fuse is an indication of something
gone wrong. Replacing the fuse is akin to ignoring
a symptom. Why did the fuses blow?

Part 2b is an understanding of the technical properties
of fuses. The terms "fast-blow" and "slow-blow" are
relative. A slow-blow fuse blows slower than a fast blow,
and, guess what, a fast blow fuse blows faster than a slow
blow..

You migt be surprised to learn that at twice the rated
current, a fast blow fuse will hold for a LONG time,
as will a slow-blow fuse. A long time can mean an hour.

If you have a fault in your amplifier, the time it takes for
even the fastest fuse to blow is FAR longer than it could
take to damage a curcuit.

With these two broad issues in mind, my course, if it
were me, would be to a) find out why the fuses blew to
begin with and b) trust the people who designed the amp
to begin with to be the best source of technical advice
on the amp and its operation.

[Peter Wieck]

On Jul 25, 5:51*pm, wrote:

If you have a fault in your amplifier, the time it takes for
even the fastest fuse to blow is FAR longer than it could
take to damage a curcuit.

With these two broad issues in mind, my course, if it
were me, would be to a) find out why the fuses blew to
begin with and b) trust the people who designed the amp
to begin with to be the best source of technical advice
on the amp and its operation.

Mpfffff... good advice as far as it goes, but it does not go nearly
far enough.

For the sake of this discussion, there are three types of fuses
commonly used in audio stuff:

a) Standard (fast-blow) fuse: A simple current-limiting device with a
very specific failure point and very limited capacity for over-current
and a quick failure mode. Typically used for situations where there is
no need for surge protection and no expectation for over-current
tolerance. Most often used for speaker-fuse applications where a hard
upper limit to speaker current is required or desired. Very rarely
(but not -never-) used as mains-fuses. Most often seen fusing
individual internal elements in audio equipment.

b) Slow-Blow fuses: As above, except that the fuse element is heat-
sinked such that it can tolerate a variable amount of over-current for
a variable period of time - depending on the amount of over-current.
Also used for speaker applications where the upper limit is not so
hard, but the amount of over-current the speakers can tolerate is a
time-over-current calculation. Sometimes seen as mains-fuses in audio
equipment, but typically the better the equipment design, the less
likely a slow-blow fuse will be used for mains protection.

c) Dual-Element fuses: An entirely different beast than either of the
above. A D/E fuse will tolerate a very high INITIAL SURGE, but then
revert to "fast-blow" behavior after that surge. These fuses are
(relatively) expensive and (relatively) hard to find at places like
Radio Shack or the equivalents. But they are easy to find at Mouser,
Digikey, Newark and the like. And they are much, much cheaper than
fried equipment - and have half-a-chance of protecting that equipment
where the other fuses will not.

Notes:

1. A fast-blow fuse capable of handing turn-on surges for most audio
equipment, especially tube equipment, need to be rated somewhere
between 2 and 4 X the normal operating current requirements of that
equipment. So, a failure within that equipment that is expressed as
heat but only draws 20% more than the normal operating current will
cook that equipment until something _other_ than the fuse fails. Fast-
Blow fuses in this application are to protect the real-estate, not the
equipment.

2. Slow-Blow fuses can address some of this. They are designed to fail
on a curve where a small over-current will be tolerated for a
(sometimes very long) period of time, large over-currents for less
time, and dead-shorts not at all. Same issue as above, but there is
_at least_ some hope that the fuse will fail before the equipment is
thoroughly cooked.

3. Dual-Element fuses are the answer for this. Their rating can be
tailored very close to the actual operating current, yet tolerate a 2
to 10 X starting surge. They come in 1/10A through ManyA ratings in
tiny increments as little as 0.02A. And, they are $1 fuses vs. $0.15
fuses from legitimate, quality manufacturers in small quantities. They
also do not tolerate rapid cycling (so should not be used for speaker
applications) - they need to cool down between cycles or they will
fail at turn-on, they age over time and will fail due to age - but all
that is a function of their design and the fact that they actually do
protect *BOTH* the equipment and the real-estate. I use them
exclusively for mains-fuses - more on this later.

I will bet that ADCOM did not state that Slow-Blow fuses were OK, but
more likely stated that you could use them in place of much-higher
rated Fast-Blow types. I also expect that they responded to your need
to procure them locally vs. purchasing more apt fuses by mail-order.

My personal habit with these things is to set up the equipment on a
metered variac, determine the maximum current draw under load and
install a Dual-Element fuse at/slightly below that rating. Quite
often, I have installed D/E fuses at 1/3 to 1/2 the "nameplate" rating
with excellent results and no trouble with false-failures. Funny how
with the well-designed (and made) stuff, the rating is quite close to
the actual - and most came with D/E fuses "from the factory".

Enjoy.

Peter Wieck
Melrose Park, PA

[Casper[_4_]]

YOu have a couple of issues: let's settle each in turn.

First, who do you think is going to give you better
advice on the detailed technical workings of your
Adcom amplifier: the technical department of Adcom,
or members of a general forum on audio? If your
answer is members of the forum, how might you deal
with answers that contradict one another?

If it were my amplifier, I'd be far more inclined to trust the
advice of the manufacturer than some otherwise unknown
collection of advice from the web, but that's satisfying my
criteria.

You ever hear the phrase, "get a second opinion"?

Your point is a valid, but not complete. As a person who has genuinely
experienced severe failures with professional and expert advise (I
won't expound on those unless necessary), I can assure you I take
everything I hear or read with a large grain of salt.

I am not an electrical or electronic engineer. I asked my question to
see if anyone else has experienced this problem, either with Adcom or
other brands, and hear what were their remedies, if any. There appears
to be some fairly knowledgeable people posting in the newsgroup.

If you want, get a statement in writing from the
manufacturer stating their recommendation is to use
the slo-blo fuses and, if your amp blows up, you have
a legal leg to stand on if it can be shown the amplifier
failed as a direct consequence of using the wrong
fuse.

Thanks for pointing that out but I can assure you I am already well
aware of this process.

The second point is putely technical and has a couple
of parts to it.

Part 2a is to determine exactly why the fuses blew to
begin with. A blown fuse is an indication of something
gone wrong. Replacing the fuse is akin to ignoring
a symptom. Why did the fuses blow?

Without trying to sound sarcastic, I imagine a fuse blowing would be
an indication of something wrong. I would love to determine that
cause.

This unit only has two fuses,which blow randomly, meaning there
appears to be no consistancy in the timing of their failure.
Increasing volume, changing tone or any other alterations to the
system cannot 'cause' the fuses to blow. At times they will operate
for months without a problem before a sudden failure, while other
times a second set might blow almost immediately. I have even noted
local brown-outs, spikes and surges which do not coincide with any
failures. And yes, I do have this unit on a power protection unit.

I have read that some people have experienced fuse failures with the
GSP-560 but none of those reviews stated even a potential cause. If
you know how I can determine the cause, I am open to suggestions.

(Example: http://www.audiokarma.org/forums/arc.../t-160172.html)

Part 2b is an understanding of the technical properties
of fuses. The terms "fast-blow" and "slow-blow" are
relative. A slow-blow fuse blows slower than a fast blow,
and, guess what, a fast blow fuse blows faster than a slow
blow..

You migt be surprised to learn that at twice the rated
current, a fast blow fuse will hold for a LONG time,
as will a slow-blow fuse. A long time can mean an hour.

If you have a fault in your amplifier, the time it takes for
even the fastest fuse to blow is FAR longer than it could
take to damage a curcuit.

Interesting. As I said, I am not an electrical engineer, but I have
been told by several that slo-blo fuses can cause damage to various
electronics if not configured to use those types of fuses.

With these two broad issues in mind, my course, if it
were me, would be to a) find out why the fuses blew to
begin with and b) trust the people who designed the amp
to begin with to be the best source of technical advice
on the amp and its operation.

Again, if you have suggestions on how I can isolate the cause, I'm all
ears. As to the second, I hold to hearing "second opinions" (third,
fourth and so on) per personal experience with deceptive
manufacturers. It's part of my criteria before jumping in feet first.
I like to make as much of an informed decision as I can where some
things are concerned, and costly equipment is one of those areas.

`Casper

Train your mind to test every thought, ideology, train of reasoning,
and claim to truth.

[Bob Eld]

"Casper" wrote in message
...
Hi all!

I have a concern regarding fuses in my Adcom GSA-560 amp. The orginal
fuses blew and I was out of backups. I went to Rat Shack but they did
not have any more in that size except for slo-blo. I searched the
internet for them and came up empty handed. So, I contacted Adcom, who
sent me fuses, but they are slo-blo. Adcom's original manual states
not to use slo-blo on this unit. So being cautious, I called Adcom and
the person (non-tech) I spoke with assured me the technicians say
using slo-blo is fine. I'm still not certain if I should use the new
fuses. Any input on this? Am I just being overly cautious? Or should I
be wary of slo-blo causing more damage to my unit?

Thanks!
`Casper

Question: Why did the original fuses blow? Whenever a fuse blows there has
to be a reason and you haven't even mentioned the reason. Are you sure that
the conditions that blew the fuse are OK and all you need do is replace a
fuse(s)? I'd dig deeper if it were my amp.

Why not get the right fuse(s)? If rat shack doesn't have them get them from
Mouser, Digikey or other electronic distributor.

I personally would never take the word of some bimbo out in the front office
unless she got the replacement spelled put in the manual or provided a
service bulletin for the change.

The way you talk about this, being out of back-up fuses suggests that this
amp may blow fuses all of the time? Maybe the originals were under rated and
the engineers decided to go to a slow blow to fix a problem with the
product. If so, it would be nice to get this in writing as a service
bulletin on the amp.

If the amps are still in warrantee, don't do anything that might void the
warrantee.

[Casper[_4_]]

Question: Why did the original fuses blow? Whenever a fuse blows there has
to be a reason and you haven't even mentioned the reason. Are you sure that
the conditions that blew the fuse are OK and all you need do is replace a
fuse(s)? *I'd dig deeper if it were my amp.

I wish I knew the cause. If I knew the reason I would have stated it.
This is the only piece of gear that blow fuses. Adcom offered no
answer except to examine the unit.

Why not get the right fuse(s)? If rat shack doesn't have them get them from
Mouser, Digikey or other electronic distributor.

When I searched for this size, I found a distributor but they would
only sell in quantity. I don't need hundreds of fuses.

I personally would never take the word of some bimbo out in the front office
unless she got the replacement spelled put in the manual or provided a
service bulletin for the change.

The type of fuses required are marked directly on the board in the
amp. The replacements were directly from Adcom, per their tech.

The way you talk about this, being out of back-up fuses suggests that this
amp may blow fuses all of the time? Maybe the originals were under rated and
the engineers decided to go to a slow blow to fix a problem with the
product. If so, it would be nice to get this in writing as a service
bulletin on the amp.

The unit did not come with 'back-up' fuses. I don't keep spares around
as I've never had a need. I have replaced the fuses a few times,
meaning more than a package of three and far less than a case. [3-10
times?] Fuses under-rated? Or Adcom error? I had hoped it was already
a bulletin but it appears Adcom has had, or has, no interest in doing
so, neither have they, as far as I can find, issued a reason for the
failure.

If the amps are still in warrantee, don't do anything that might void the
warrantee.

Long past warranty, which is why I doubt Adcom would issue any further
info on problems with the unit. It's called EoF (End of Life).

[w_tom]

On Jul 28, 7:51*pm, Casper wrote:
You ever hear the phrase, "get a second opinion"?

"Get a second opinion" ... from responsible sources. Finish the
quote. After visting your doctor, do you get a second opinion from a
fortune teller's crystal ball?

You have a second opinion. The unit came with the correct fuses.
Your second opinion is the tech manual that also says those fuses must
be installed. How may hearsay opinions do you also want?

Meanwhile, go to someplace that will always have these fuses if
available:
www.digikey.com
www.mouser.com
www.alliedelec.com
www.newark.com
www.jamesco.com

No reason to waste times asking sooth sayers in the newgroup what
they think. They are not designers who installed the original fuses
AND who wrote the tech manual. This is not rocket science. Everyone
who disputed the tech manual is also been a source of hearsay.

To discover a cure for cancer, go find a priest. He is just as
reliable as a doctor specializing in cancer treatments?

And finally, was the design found defective. Was the design changed
because fast blow fuses tripped too often? A tech support rep who is
responsible would say so. But one who is being politically correct
might not or could not bother to learn what he was supposed to know.

[Casper[_4_]]

Thank you for the additional information on fuses, it was very
informative.

I will bet that ADCOM did not state that Slow-Blow fuses were OK, but
more likely stated that you could use them in place of much-higher
rated Fast-Blow types. I also expect that they responded to your need
to procure them locally vs. purchasing more apt fuses by mail-order.

Perhaps I should clarify this better. Adcom supplied me with the
fuses. I have both the name of the gentleman I spoke with and a letter
from Adcom. The GSP-560 has four fuse sockets, all labeled 4A/250V
fast-acting 250v, 5x20mm GMA-Type fuses. The only fuses I was able to
obtain, until Adcom's package arrived, were 3A/250v FA (Fast-Acting).
The paperwork from Adcom states they sent me 4A AL Mini (2CM) GMA
fuses but the actual fuses in the package are 5A/250v slo-blo. I
initially thought perhaps Adcom made an error sending me the wrong
fuses (wrong pick-bin?), but they said those are the fuses they use
and will work fine in the amp. I realize these 5A fuses will take
longer to blow than the 4A and am merely concerned that the unit may
incur damage in the time it takes these fuses to blow as opposed to
the original prescribed ones, expecially as this is an older unit.

After reading reports of other GSP-560 owners having the same fuse
problem, it begs the question what is the cause, especially since they
do not blow frequently. I am personally neither equipped or
knowledgeable enough in this area to attempt a technical
determination. I had considered sending the amp out but the cost of
that, plus any repairs, may be considerably more than the amp is
worth. Given newer technology, it may be more practical to completely
replace. So I guess perhaps my question should be, " .. is it worth
it?"

My personal habit with these things is to set up the equipment on a
metered variac, determine the maximum current draw under load and
install a Dual-Element fuse at/slightly below that rating. Quite
often, I have installed D/E fuses at 1/3 to 1/2 the "nameplate" rating
with excellent results and no trouble with false-failures. Funny how
with the well-designed (and made) stuff, the rating is quite close to
the actual - and most came with D/E fuses "from the factory".

Unfortunately those tests are beyond my means. The only local repair
place who still does in-house repairs advised me they will most likely
be unable to define the cause. However with the additional detailed
information about fuses, I feel a bit more confident about
substitutions. I got some 5A250v FA and am currently using them in two
of the slots and they have yet to fail. The other two slots still have
the original 4A250v FA and have not yet failed.

Enjoy.

Peter Wieck
Melrose Park, PA

Thanks for all the information and advice. I've been quielty reviewing
this newsgroup for some time and slowly adding to my knowledge in hi-
fi, especially in areas I do not normally tread.

With music making it's changes from LP to CD to digital files (mp3,
lossless, etc,.), I have started thinking it might be time for me to
do the same, ergo my interest in this group and 'news' in this ever
progressive arena. While I still haven't completely convinced myself
to part from my old audio habits, I am open to change. I started many
years ago by passing on my LPs to go to tape and then to CD, which is
the current majority of my collection. At this time I have yet to
convince myself to give up my CDs, but I have been converting them
over to the computer since I spend much of my time there. In pondering
my present listening habits, I've been looking at my existing setups
and considering making the changes in them to suit my current needs.
Thus I have been spending more time with my older equipment in
consideration of what I use, what I really don't, what can stand an
upgrade, and, if so, to what? I suspect, from what I have been reading
here, this is a perpetual question for those of us in love with
music .. or audio-nirvana.

[Peter Wieck]

On Jul 29, 9:41*pm, Casper wrote:

I realize these 5A fuses will take
longer to blow than the 4A and am merely concerned that the unit may
incur damage in the time it takes these fuses to blow as opposed to
the original prescribed ones, expecially as this is an older unit.

YIKES!!

A 5A slow-blow fuse may _never_ blow as compared to a 4A FA-type - all
the while letting the magic smoke out of your amp. I do not get a warm-
and-fuzzy feeling about what you have written, what ADCOM has told you
or anything else going on around this discussion. Fuses are simple in
concept, not-quite-but-very-nearly as simple in application. Get the
correct fuses.

http://www.mouser.com/Search/Product...n4RteGlA%3d%3d

The voltage rating is not relevant if you in the USA and operating at
standard wallplate voltage.

Much more on fuses he

http://www.circuitprotection.ca/fuseology.html

There is no need to upgrade vintage equipment if it is otherwise
operating properly and you are otherwise happy with it. It, like
anything else, does require the correct care-and-feeding however.

Just an aside: if the factory-specified fuses keep blowing *AND* this
seems to be a problem with the species in general *AND* there are no
apparent collateral problems *AND* there has been no degredation in
performance *AND* no apparent signs of trouble - smells, heat, buzzes,
smoke - it could simply be that the original specified fuse was too
light for the circuit in actual practice. And with the general
increase in line-voltage in parts of the US over the last 10 years, a
marginal design *COULD* cause trouble. *SO* - get the correctly rated
fuses - buy a box of them - and at least attempt to protect the
equipment rather than just the real-estate. But leaping from a 4A FA
to a 5A Slow-Blow - well, you may as well cut a piece of 5mm copper to
the correct dimensions and drop that in place as far as the equipment
is concerned.

Peter Wieck
Melrose Park, PA

[Bob Eld]

"Casper" wrote in message
...
Question: Why did the original fuses blow? Whenever a fuse blows there
has
to be a reason and you haven't even mentioned the reason. Are you sure
that
the conditions that blew the fuse are OK and all you need do is replace
a
fuse(s)? I'd dig deeper if it were my amp.

I wish I knew the cause. If I knew the reason I would have stated it.
This is the only piece of gear that blow fuses. Adcom offered no
answer except to examine the unit.

Why not get the right fuse(s)? If rat shack doesn't have them get them
from
Mouser, Digikey or other electronic distributor.

When I searched for this size, I found a distributor but they would
only sell in quantity. I don't need hundreds of fuses.

I personally would never take the word of some bimbo out in the front
office
unless she got the replacement spelled put in the manual or provided a
service bulletin for the change.

The type of fuses required are marked directly on the board in the
amp. The replacements were directly from Adcom, per their tech.

The way you talk about this, being out of back-up fuses suggests that
this
amp may blow fuses all of the time? Maybe the originals were under rated
and
the engineers decided to go to a slow blow to fix a problem with the
product. If so, it would be nice to get this in writing as a service
bulletin on the amp.

The unit did not come with 'back-up' fuses. I don't keep spares around
as I've never had a need. I have replaced the fuses a few times,
meaning more than a package of three and far less than a case. [3-10
times?] Fuses under-rated? Or Adcom error? I had hoped it was already
a bulletin but it appears Adcom has had, or has, no interest in doing
so, neither have they, as far as I can find, issued a reason for the
failure.

If the amps are still in warrantee, don't do anything that might void
the
warrantee.

Long past warranty, which is why I doubt Adcom would issue any further
info on problems with the unit. It's called EoF (End of Life).

All of that being the case, just stick in the Adcom supplied slo-blo's and
keep your fingers crossed. No point in beating a dead horse!