Solid State Guitar Amp Forum | DIY Guitar Amplifiers

can i ask about repairs on this board?
looking for some ideas on what could be causing this horrid sound coming from my randall rg100es guitar amp head. when i turn the master past 4 the amp starts howling. not the high pitched positive feedback sound but a low midrangybassy hollow 'howl" that drives the speaker crazy. the speaker starts to vibrate real hard like its gonna blow up. i all i have plugged in is a guitar. kinda lost on this one :-\

thanks for any responses.

Yup, you sure can, we help with repairs all the time.

As far as your problem goes, does it do it only when a guitar is plugged in?

Spring reverb picking feedback?

I think i got the same problem...i got a randall rg 80 es that i scored for free.  As soon as i plug it into the speakers i get a high pitch steady squeal no matter the volume.  any ideas of what the problem could be??

It is quite easy to regognize the problem of a spring reverb picking feedback as it creates a steadily "swelling", quite low pitched sound that increases in amplitude until the speakers start to rattle seriously. This usually takes few seconds. The sound can also be "altered" by punching the amplifier cabinet - as it is shaking the springs. Fixing it has likely something to do with checking that the reverb tank is mounted on a way that damps most vibrations. tonetechtx: Did you find out what was the problem?

troc69: I assume your amp starts squeling immediately after you have plugged it in to a speaker system. If so, then your problem likely isn't spring reverb picking up feedback. This sounds like some part of the circuit after the volume control is oscillating. Unfortunately, that could be caused by virtually anything - it is tough to say anything concrete without a schematic. Open it up and see if solder joints and components look allright. Good candidates for starting troubleshooting are components and circuit areas that look repaired/modded - and, of course, burned.