Hello all, so as the title implies, I have a Fender Princeton Chorus red knob solid state amplifier, one of the early ones (about 1988 or so). The problem that I am having with it is the volume is fluctuating. After about a minute of normal playing at the set volume it will drop to about 60% of that for a minute or so then go back to the set volume. Its not intermittent, it does it all the time and has only been doing it for about 3 - 4 weeks.

Any clues to what could be causing it?
Have you checked the tubes?
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I think it's the tubes

Really though I have no idea, what's the price of the amp, are they sought after?
If not might be easier to just buy a new amp.

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I've had (more or less) the same problem with another amp of mine. It's probably the power supply. Take it to a tech and get him to check it out.

Mine broke because I used it (once) through an unstable power generator (you know, the kind you pour diesel in and electricity comes out). Maybe you did something similar?
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Could be a lot of things. First thing to try is jiggling the pots, especially the volume and gain of course. If that has no effect, try pulling the plug out of the input and plugging it back in. Then try the same with the speaker cable (if it isn't hardwired). If any of those has an effect then you've discovered the fault.
It could also be the guitar cable or the guitar itself, try others.
Beyond that you are looking at something more difficult and most likely cost more to have a tech find and fix than the amp is worth.
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Is it a smooth change in volume or does it kind of 'pop' between different levels? Any static or other noises when it happens? Loose wiring, such as speaker wiring, will make other noises not just volume changes in my experience.

Unfortunately it's either something really simple, like a loose wire, or it's likely not worth fixing.
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Thanks guys, as far as value goes, these old girls are on the way up, 5 years ago you couldn't give them away, 3 years ago they went for about $150, now they go for around 300. They are supposedly one of the best clean amplifiers getting around. There is no noise as far as switching between clean and dirty, or when the (fault occurs) volume drops. One thing it does do is pop very loud when it gets turned off at the switch, not every time but 50% would be close. Whether that has anything to do with it I do not know. Oh yeah went to check the tubes but Im stuffed if I can find them. The closest ones are in a draw in my desk and they are fine...