Thanks JM,

I was in fact doing exactly what you mentioned. Resoldered the large caps and jacks etc, and lo and behold, everything is back in order, even the channel-switching delay has disappeared (capacitor I'm sure).

One weird thing I noticed.. the input jacks and line in/out have been switched. The input jacks are stereo and the line in/out are mono. I'm pretty sure I should just replace all of them, would you agree? Will these do?

http://cgi.ebay.com/Amp-Mono-Cliff-Input-Jack-4-PC-Terminal-Mount-S-H503_W0QQitemZ170371640384QQcmdZViewItemQQptZGuitar_Accessories?hash=item27aaf0ec40

Ok new symptoms, new problems:

-On channel A, there is now nothing.
-On channel B, there is a very loud white noise sound. I believe it's a concoction of radio signals, occasionally you can pick out voice/music/ghosts, but the guitar has no effect.
-Plugging a guitar into Line In, it works and sound great.

Switching from channel A to B is also very slow. Finally, if I tap on one of the big wide caps with the butt of a screwdriver on channel B, the radio noise seems to go away.

Hey guys,
Ok did some more testing. First of all the contact cleaner worked well on the pots, less random noise when changing stuff now.

The rectangular giant resistors are in the area that had been repaired, and I can see for sure that one of the feet (I believe from the 10ohm one?) has pulled off from the circuit board. I ran a jumper from the pin to next contact and put it all back together and things seem much better. Still when I had it on really high I hit a point where it gave up, so I think vibration is still an issue.

Secondly, I tried flexing the input cable a bit at the jack and it seems there's a problem with the 0db input (despite resoldering) so I think I need a replacement.

There's also a significant amount of resistor dust in that area.. will these things increase in resistance over time? Should I just replace them?

Thanks guys, I'll pick up some contact cleaner today and check those jacks.

Phatt: I wouldn't say the the LED and audio problems are "in sync", it just seems like two problems that are related. For example, when the audio starts to fade out, the LED stays on fine. I just noticed when I switch channels and switch back, the LEDs seem to take time to react.

Enzo: I did whack it once, and it reacted.

Hi guys!

Picked up this Crate amp the other day. Seemed to be working but the sound fades to nothing. Occasionally it'll be fine for like 10 minutes, the do nothing for a few minutes, then come back to life. I also noticed that pressing in the channel select button, then pressing it again, the channel doesn't change quickly, it takes 30 seconds to a minute for B's LED to turn off and A's LED to turn back on.

I noticed that by turning up the reverb, then disconnecting and reconnecting one of the plugs to the reverb box the sound will return, however I'm fairly certain the reverb box isn't the problem.

I took a look at the electronics and it's definitely been repaired before. There is a section that looks burned (and was repaired). I tried reflowing some of the iffy looking solder points around that area but it didn't fix the problem.

This all seems to point to transistor or capacitor problems, would I be correct?