Amp acting strange, any ideas what might be wrong?

[jangles642]

Ok so I bought a used amp (Rouge GS-100) It worked for a bit, but now when I turn it on and play, it is very quiet...like abnormally 'I can barely hear anything' quiet. It's quiet UNLESS I turn the volume all the way up(still quiet at this point) and strum real hard. At this point it crackles a bit and then "kicks in" and has normal very loud volume. I can turn the volume back down and play on it normally. It will stay like this for maybe 10-20 minutes, then it dies again. If I repeat the "kick start" process, it will start working again.

What the hell is going on here? Help would be greatly appreciated...I'm playing live on Thursday, and it would suck to be one amp short!

[Enzo]

Does it have effects loop jacks?  Or headphones jack?   next time it does this, try poking a plug into the FX return briefly.  or take a spare cord and plug it from send to return directly.

[Roly]

These are common signs of a dirty connection somewhere in the signal path.  A common cause is dirt in the bridging contacts of the Fx Loop sockets.

By jumpering them with a lead you take these contacts out of circuit, replacing them with the lead.  This often effects a "cure", however the fault is still there and these contacts need to be cleaned.

Other causes are dirty input and output sockets, dirty or damaged pot tracks, and less commonly any plug and socket connections internally.


PS a some clear pix of the front, back, and the underchassis or internals would be a help considering the circuit is not yet available.

[jangles642]

Update: I tried using a cable and connecting effects return to send...no help. But, I did try plugging my guitar directly into the effects return and that helped the volume a little, but not much over the normal inputs. I'll get pics up soon. Thanks for the suggestions so far!!!!

[jangles642]

Ok so I took the amp apart and sprayed contact cleaner (from Radioshack) in all the pots and in all the jacks, and then just sprayed a ton all over the circuit board hah. I also made sure all the plastic wire connecters were secure. I put the amp back together and....MAGIC!!! IT WORKS!!!!!!!!!!!!!!!! At least for now. We will see if it is still functional tomorrow.

I really cant believe it, because everything actually looked really clean on the inside of the amp. I was not expecting that to work!

Thanks guys/gals for the help!!!!!!

[Roly]

Generally an intermittent connection has to be in a pretty bad way before you can actually see the dirt causing the problem.

On the down side you haven't actually located the fault, so you can't be sure you've actually repaired it; but on the upside you know the amp is basically working okay, and you can be pretty sure now that it's only a dirty contact somewhere.

If it happens again, (with the power off and unplugged) you can work/scrub all the connectors by unplugging them and plugging in again.

If you feel okay working under a live chassis, you can feed a small signal in, say from an MP3 player, and try gently tapping with a chopstick or similar insulated prod around the various connections and see if you can localise it, or even pin down the precise connection that is giving you trouble, then give a good wipe, squirt, wipe (but I would avoid giving the while PCB a bath, these cans of "instant technician" sometimes contain light fractions that some components don't like - contact cleaner is for contacts.

Don't forget to report back and let us know how it turns out.

HTH