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Post subject: Fender FM 100H losing volume
Posted: Sun Aug 17, 2014 10:49 am
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Hey All --

Got a question about my FM 100H amp head. Its 100W, solid state with a clean and dirty channel. I picked it up a few months ago used (obviously!) and its starting to have an issue with the volume. When I first bought it, it did have some crackling in the volume pot, but after some contact cleaner the crackling went away and the amp was great for a while. Now, the amp will lose all volume completely while playing or fluctuate from very low to where the dial is set. At other times, I can crank the volume to 10, and it still sounds as if it is set at two.
Is this an issue with my volume pot, or is the power fluctuation an indicator of some other issue? Any help would be appreciated!

Thanks --

Bud


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Post subject: Re: Fender FM 100H losing volume
Posted: Sun Aug 17, 2014 12:04 pm
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Hi jerrybud,

It could be the pot. Some pots have plastic instead of carbon for the resistance, and contact cleaner can melt the plastic, ruining the pot. Actually, contact cleaner should not be used for anything but contacts and other metal parts, it is not good for most electronics. There are spray cleaners for pots, but even that can ruin the ones that have plastic inside.

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Post subject: Re: Fender FM 100H losing volume
Posted: Sun Aug 17, 2014 6:04 pm
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shimmilou wrote:
Hi jerrybud,

It could be the pot. Some pots have plastic instead of carbon for the resistance, and contact cleaner can melt the plastic, ruining the pot. Actually, contact cleaner should not be used for anything but contacts and other metal parts, it is not good for most electronics. There are spray cleaners for pots, but even that can ruin the ones that have plastic inside.


At least in the case of Frontman 212R, which I understand is essentially the same amp with two 12" speakers, the pots are sealed. If the pot is bad, replacement may be the only solution.

Jerrybud, are you any good with a soldering iron? As this is a single circuit board amp, be careful.

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Post subject: Re: Fender FM 100H losing volume
Posted: Mon Aug 18, 2014 4:34 pm
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I'm not too shabby with soldering iron so I'll try replacing the pot. Question is, what kind of volume pot do I replace it with? I have some new 250k and 500k pots for guitar, but I'm not sure if I can use these....

Thanks for all the help!!

Bud


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Post subject: Re: Fender FM 100H losing volume
Posted: Mon Aug 18, 2014 7:11 pm
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jerrybud wrote:
I'm not too shabby with soldering iron so I'll try replacing the pot. Question is, what kind of volume pot do I replace it with? I have some new 250k and 500k pots for guitar, but I'm not sure if I can use these....

Thanks for all the help!!

Bud


If I am correct that FM100=Frontman 212 as far as the amp, this should answer your question:

http://support.fender.com/schematics/gu ... ematic.pdf

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