# Volume dropping randomly in a solid state amp



## kat_ (Jan 11, 2007)

I picked up an 80s solid state Randall on the weekend and it's having a volume issue. It will stay at normal volume for about a minute, then drop down to nearly silent for a minute, then back to normal, then back to silent, and keep repeating that cycle.

I need to open it up for a good cleaning anyway and I have a schematic so I can check everything over. Is there any particular area that's likely to be causing this?


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## mhammer (Nov 30, 2007)

One possibility is residue/dirt build-up inside the volume pot. A good shpritz with contact cleaner can help.

Another is off-spec caps in the power supply, though I need to ask if the tone remains the same and only the volume changes.


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## kat_ (Jan 11, 2007)

Cleaning the pots did help. Thanks.

I think the caps are leaking too. There's a noticable hum even with all of the knobs turned to 0 and when I switch the amp off there's a slight delay then a pop. My old Randall did the same thing though so I'm not too bothered by it. The hum doesn't get any louder as I turn up, so even with the volume on 1 I drown it out.

Thanks for your help. I need to play more to test more of it out now.


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## mhammer (Nov 30, 2007)

The good news is that if it IS the caps in the power supply, it's a cheap fix. Once you're in the range of 63v or lower, even large-value caps (2200uf and even larger) aren't all that expensive, and are often easily found locally.

It rarely hurts to upgrade the PS caps, too. If they are currently 1000uf, try 2200uf instead. If they're 2200uf, try 3300uf or 4700uf. It'll take longer for them to drain after the power is cut, but it'll give you a little more reserve power when you slam the strings.

The other thing is that cap sizes have probably come down in size since the amp was built, so you'll likely be able to fit a higher value in the same physical space.


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## kat_ (Jan 11, 2007)

They're currently 6800 uf, 50 volts and the size of C batteries. Next time I'm at Active I'll check for replacements.


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