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Mal Thomas Mal Thomas is offline
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Posts: 26
Default Need Help with speaker control

I have just become aware that one of the variable resistors (Mid Frequency
Attenuator) on the rear of one of my speakers is on the fritz.

Either the MF driver cuts out and/or the resistor, when turned, is noisy. I
have managed to 'clean' the resistor somewhat by turning it back and forth a
few times, but it is still a little noisy.

http://flickr.com/photos/22432327@N02/3136967471/ photo here.

Now I very little knowledge of the internals of a speaker so I would
appreciate some advice from someone who is more qualified than I am.

Looking at the panel in the photo, I would presume removing it would give me
ready access to the resistor, but can I expect any sealant here or are the
screws the only thing holding it in ?

I know I can get replacements of these things from an electronics components
shop, so any clue as to the type or rating would be appreciated.

Failing replacement, can I simply bypass it by removing it altogether?. I
usually run the MF one wide open, so I won't be too bothered if I lose the
control.

At the moment I have managed to find a spot where the driver is working, but
I'd prefer to find a more permanent solution.

TIA
Cheers
Mal
Oz

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Engineer Engineer is offline
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Location: Thornhill, Ontario
Posts: 104
Default Need Help with speaker control

G'day, Mal.
If you have even entry level competence with electrical stuff and a
soldering iron do not hestiate to go in, do the forensics and fix it (don't
bypass it, that would likely screw-up the speaker's sound balance.) The
potentiometer may well clean up with switch cleaner. If not a replacement
should be easy to find. Make sure that removed plates, etc, are well sealed
when you put it all back - not difficult to do: thin foam draft excluder
strip under them works well. Stick anything that need sticking with contact
adhesive. Ensure no dry joints.
Good luck!
Cheers,
Roger

"Mal Thomas" wrote in message
...
I have just become aware that one of the variable resistors (Mid Frequency
Attenuator) on the rear of one of my speakers is on the fritz.

Either the MF driver cuts out and/or the resistor, when turned, is noisy.
I
have managed to 'clean' the resistor somewhat by turning it back and forth
a
few times, but it is still a little noisy.

http://flickr.com/photos/22432327@N02/3136967471/ photo here.

Now I very little knowledge of the internals of a speaker so I would
appreciate some advice from someone who is more qualified than I am.

Looking at the panel in the photo, I would presume removing it would give
me
ready access to the resistor, but can I expect any sealant here or are the
screws the only thing holding it in ?

I know I can get replacements of these things from an electronics
components
shop, so any clue as to the type or rating would be appreciated.

Failing replacement, can I simply bypass it by removing it altogether?. I
usually run the MF one wide open, so I won't be too bothered if I lose the
control.

At the moment I have managed to find a spot where the driver is working,
but
I'd prefer to find a more permanent solution.

TIA
Cheers
Mal
Oz



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Mal Thomas Mal Thomas is offline
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Posts: 26
Default Need Help with speaker control



On 1/01/09 2:15 AM, in article ,
"engineer" wrote:

"Mal Thomas" wrote in message
...
I have just become aware that one of the variable resistors (Mid Frequency
Attenuator) on the rear of one of my speakers is on the fritz.

Either the MF driver cuts out and/or the resistor, when turned, is noisy.
I
have managed to 'clean' the resistor somewhat by turning it back and forth
a
few times, but it is still a little noisy.

http://flickr.com/photos/22432327@N02/3136967471/ photo here.

Now I very little knowledge of the internals of a speaker so I would
appreciate some advice from someone who is more qualified than I am.

Looking at the panel in the photo, I would presume removing it would give
me
ready access to the resistor, but can I expect any sealant here or are the
screws the only thing holding it in ?

I know I can get replacements of these things from an electronics
components
shop, so any clue as to the type or rating would be appreciated.

Failing replacement, can I simply bypass it by removing it altogether?. I
usually run the MF one wide open, so I won't be too bothered if I lose the
control.

At the moment I have managed to find a spot where the driver is working,
but
I'd prefer to find a more permanent solution.

TIA
Cheers
Mal
Oz


G'day, Mal.
If you have even entry level competence with electrical stuff and a
soldering iron do not hestiate to go in, do the forensics and fix it (don't
bypass it, that would likely screw-up the speaker's sound balance.) The
potentiometer may well clean up with switch cleaner. If not a replacement
should be easy to find. Make sure that removed plates, etc, are well sealed
when you put it all back - not difficult to do: thin foam draft excluder
strip under them works well. Stick anything that need sticking with contact
adhesive. Ensure no dry joints.
Good luck!
Cheers,
Roger

Many thanks Roger. Yes I do have some soldering skills (a legacy from
building model railways for some years!).

I haven't open the cabinet yet, so can I expect to find the rating or 'part
#' of the potentiometer stamped on it somewhere ? Or is there some
'standard' type used for this purpose? (it is here that my experience and
knowledge fails me).

I'll try the switch cleaner route first though.

Regards
Mal
Oz




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Engineer Engineer is offline
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Location: Thornhill, Ontario
Posts: 104
Default Need Help with speaker control


"Mal Thomas" wrote in message
...


On 1/01/09 2:15 AM, in article ,
"engineer" wrote:

"Mal Thomas" wrote in message
...
I have just become aware that one of the variable resistors (Mid
Frequency
Attenuator) on the rear of one of my speakers is on the fritz.

Either the MF driver cuts out and/or the resistor, when turned, is
noisy.
I
have managed to 'clean' the resistor somewhat by turning it back and
forth
a
few times, but it is still a little noisy.

http://flickr.com/photos/22432327@N02/3136967471/ photo here.

Now I very little knowledge of the internals of a speaker so I would
appreciate some advice from someone who is more qualified than I am.

Looking at the panel in the photo, I would presume removing it would
give
me
ready access to the resistor, but can I expect any sealant here or are
the
screws the only thing holding it in ?

I know I can get replacements of these things from an electronics
components
shop, so any clue as to the type or rating would be appreciated.

Failing replacement, can I simply bypass it by removing it altogether?.
I
usually run the MF one wide open, so I won't be too bothered if I lose
the
control.

At the moment I have managed to find a spot where the driver is working,
but
I'd prefer to find a more permanent solution.

TIA
Cheers
Mal
Oz


G'day, Mal.
If you have even entry level competence with electrical stuff and a
soldering iron do not hestiate to go in, do the forensics and fix it
(don't
bypass it, that would likely screw-up the speaker's sound balance.) The
potentiometer may well clean up with switch cleaner. If not a
replacement
should be easy to find. Make sure that removed plates, etc, are well
sealed
when you put it all back - not difficult to do: thin foam draft excluder
strip under them works well. Stick anything that need sticking with
contact
adhesive. Ensure no dry joints.
Good luck!
Cheers,
Roger

Many thanks Roger. Yes I do have some soldering skills (a legacy from
building model railways for some years!).

I haven't open the cabinet yet, so can I expect to find the rating or
'part
#' of the potentiometer stamped on it somewhere ? Or is there some
'standard' type used for this purpose? (it is here that my experience and
knowledge fails me).

I'll try the switch cleaner route first though.

Regards
Mal
Oz

The pot will either have a value marked on it or you will have to measure it
with an ohmmeter (preferably out of circuit.) Likely it's wirewound and in
the 10's to100 ohm range and linear type (not log or so-called "audio
taper".) If you have to replace it use a generic part but keep the value the
same. As a general rule, if all three terminals are connected in the XO,
keep to the same value as it's part of the XO design. If only two terminals
are connected you could use a slightly different value, say +/- 20%, if
that's all you can find or have to hand, but you'd get less or more control
range. My guess is that it will clean up fine.
Check any other resistors (typically wirewound types) with an ohmmeter while
you are at it - replace any open circuit ones (very unlikely to have
happened.) The inductors will be OK - just check the soldered joints - they
have close to zero DC resistance.
There will also be capacitors, typically unpolarised electrolytics (or two
back-to-back regular DC types.) These are a bit more difficult to test. You
might check for shorted ones with an ohmmeter but you have to take them out
of circuit first (meter should move up to over 5 Mohms as they charge to
meter voltage.) You can also check capacitance value against what is
printed on the label but you'd need a modern DMM with a capacitance range to
do this. Of course, I have to say "get one if you don't have one"! :-)
Good luck!
Cheers,
Roger
Canada


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Mal Thomas Mal Thomas is offline
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Posts: 26
Default Need Help with speaker control




On 2/01/09 2:09 AM, in article ,
"engineer" wrote:


"Mal Thomas" wrote in message
...


On 1/01/09 2:15 AM, in article ,
"engineer" wrote:

"Mal Thomas" wrote in message
...
I have just become aware that one of the variable resistors (Mid
Frequency
Attenuator) on the rear of one of my speakers is on the fritz.

Either the MF driver cuts out and/or the resistor, when turned, is
noisy.
I
have managed to 'clean' the resistor somewhat by turning it back and
forth
a
few times, but it is still a little noisy.

http://flickr.com/photos/22432327@N02/3136967471/ photo here.

Now I very little knowledge of the internals of a speaker so I would
appreciate some advice from someone who is more qualified than I am.

Looking at the panel in the photo, I would presume removing it would
give
me
ready access to the resistor, but can I expect any sealant here or are
the
screws the only thing holding it in ?

I know I can get replacements of these things from an electronics
components
shop, so any clue as to the type or rating would be appreciated.

Failing replacement, can I simply bypass it by removing it altogether?.
I
usually run the MF one wide open, so I won't be too bothered if I lose
the
control.

At the moment I have managed to find a spot where the driver is working,
but
I'd prefer to find a more permanent solution.

TIA
Cheers
Mal
Oz


G'day, Mal.
If you have even entry level competence with electrical stuff and a
soldering iron do not hestiate to go in, do the forensics and fix it
(don't
bypass it, that would likely screw-up the speaker's sound balance.) The
potentiometer may well clean up with switch cleaner. If not a
replacement
should be easy to find. Make sure that removed plates, etc, are well
sealed
when you put it all back - not difficult to do: thin foam draft excluder
strip under them works well. Stick anything that need sticking with
contact
adhesive. Ensure no dry joints.
Good luck!
Cheers,
Roger

Many thanks Roger. Yes I do have some soldering skills (a legacy from
building model railways for some years!).

I haven't open the cabinet yet, so can I expect to find the rating or
'part
#' of the potentiometer stamped on it somewhere ? Or is there some
'standard' type used for this purpose? (it is here that my experience and
knowledge fails me).

I'll try the switch cleaner route first though.

Regards
Mal
Oz

The pot will either have a value marked on it or you will have to measure it
with an ohmmeter (preferably out of circuit.) Likely it's wirewound and in
the 10's to100 ohm range and linear type (not log or so-called "audio
taper".) If you have to replace it use a generic part but keep the value the
same. As a general rule, if all three terminals are connected in the XO,
keep to the same value as it's part of the XO design. If only two terminals
are connected you could use a slightly different value, say +/- 20%, if
that's all you can find or have to hand, but you'd get less or more control
range. My guess is that it will clean up fine.
Check any other resistors (typically wirewound types) with an ohmmeter while
you are at it - replace any open circuit ones (very unlikely to have
happened.) The inductors will be OK - just check the soldered joints - they
have close to zero DC resistance.
There will also be capacitors, typically unpolarised electrolytics (or two
back-to-back regular DC types.) These are a bit more difficult to test. You
might check for shorted ones with an ohmmeter but you have to take them out
of circuit first (meter should move up to over 5 Mohms as they charge to
meter voltage.) You can also check capacitance value against what is
printed on the label but you'd need a modern DMM with a capacitance range to
do this. Of course, I have to say "get one if you don't have one"! :-)
Good luck!
Cheers,
Roger
Canada

Magic, even I can follow that.
Appreciate your time.

Thanks
Cheers
Mal
Oz
(..off to the shop to buy some cleaner.....and maybe a new DMM!)





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Eeyore Eeyore is offline
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Posts: 8,474
Default Need Help with speaker control



Mal Thomas wrote:

I have just become aware that one of the variable resistors (Mid Frequency
Attenuator) on the rear of one of my speakers is on the fritz.

Either the MF driver cuts out and/or the resistor, when turned, is noisy. I
have managed to 'clean' the resistor somewhat by turning it back and forth a
few times, but it is still a little noisy.

http://flickr.com/photos/22432327@N02/3136967471/ photo here.

Now I very little knowledge of the internals of a speaker so I would
appreciate some advice from someone who is more qualified than I am.

Looking at the panel in the photo, I would presume removing it would give me
ready access to the resistor, but can I expect any sealant here or are the
screws the only thing holding it in ?


Probably no sealant and it's very unlikely to be critical anway.


I know I can get replacements of these things from an electronics components
shop, so any clue as to the type or rating would be appreciated.


Take a pic of the rear, next to a ruler.


Failing replacement, can I simply bypass it by removing it altogether?


Depends how the circuit's configured.

Graham

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Eeyore Eeyore is offline
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Posts: 8,474
Default Need Help with speaker control



engineer wrote:

There will also be capacitors, typically unpolarised electrolytics (or two
back-to-back regular DC types.)


Probably worth replacing regardlesss given the likely age.

Graham

 
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