Help, How to clean/ reset a Volume Pot?

post questions / problems regarding Cyrus kit here, or any other queries of a tech nature.
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mr_yogi
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Help, How to clean/ reset a Volume Pot?

Postby mr_yogi » Mon Mar 12, 2018 12:06 pm

Hi,

Not Cyrus related, but I know there is a host of electronics knowledge in here. I've just bought a 90's Kenwood Mini System and the right channel was player quieter than the left. You can see this visually by the peak meter on the power amp. It's source independent and I've tried swapping the apeakers around. Moving the balance about half way tot he right equalised things.

So after a Google I found it was probably the volume pot as the channels are separate and they can go out of balance over time. So I decided I would clean it. Not having any contact cleaner to hand I just tried moving the volume back and forth repeatedly with the unit off. The good news is that the issue is definitely the volume pot, however the bad news is that while before the difference in output across the front speakers was small, it's now HUGE. :P In fact the right channel is barley producing anything.

Help please, HELP! ;)

mojo
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Re: Help, How to clean/ reset a Volume Pot?

Postby mojo » Mon Mar 12, 2018 1:54 pm

There are several different types of construction and materials used in potentiometers, but the most common type use a resistive carbon-based film on a substrate, with a metal contact that slides over the film. Generally what happens is that the film wears down, and the resistance increases slightly in the process (hence the volume gets lower at a given position).

And then there comes a time when the film wears through completely - initially just in places where the control is used most. This leads to complete loss of signal in those places.

Unfortunately once wear really gets hold, bits of the film start to come off and contribute to a higher wear rate. Moving the volume control through its range repeatedly is pretty much the worst thing to do, because this drags all the crud that accumulates at the end of the range that is normally used and spreads it all round the track, accelerating wear further.

Although there are ways that this can in theory be fixed, they are actually very hard to do in practice (I say this from actual experience of trying to do it), so the only really satisfactory solution is to remove and replace the pot.

(I should add for those that are not aware: only very very early Cyrus products use potentiometers for their volume controls.)

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mr_yogi
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Re: Help, How to clean/ reset a Volume Pot?

Postby mr_yogi » Mon Mar 12, 2018 9:04 pm

Bu**er. :o

Edit: Thanks for the reply.

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Re: Help, How to clean/ reset a Volume Pot?

Postby mr_yogi » Mon Mar 12, 2018 11:37 pm

Well a slight update, the issue doesn't actually seem to have gotten any worse, thank goodness. When I replaced the speaker leads, I did so fumbling around from atop the speakers, and I stuck positive cable into the gap under the string clip instead of through the hole, hence the near total lack of sound :-[