I have a problem with guitar amp. It is a Randall RG200. At idle it has a louder than usual 60hz hum. as I turn it up there is no signal until around "7 or 8". It kind of crackles through loud and powerfully. At full it will almost run. Signal does not decay it just drops out. Could someone please point me in the right direction? I would like to solve the problem myself (with help). I will try to upload jpegs.
Did it get worse over time or did it just happen suddenly?
What happend at the time it died?
I've seem guitar amps with T03 ouput devices sometimes the leads get dry joints as they see a lot of thermal stress. this is why i ask the above.
but heres my 2 cents worth:
You could have lost output from one rail by the sound of what you are saying. but the input cct may be fine.
I'd measure for:-
Dc at the output, should be close to 0 volts. ie across the speaker.
Also the VAS transistor voltage across the CE.
if you can measure the bias current would also be good to know if it still exists.
and post you findings.
also if you have an incircuit transistor tester it would come in hand.
but by the sound of it I would guess probably a driver and an ouput device have failed at the least, other than the 2 blown resistors.
What happend at the time it died?
I've seem guitar amps with T03 ouput devices sometimes the leads get dry joints as they see a lot of thermal stress. this is why i ask the above.
but heres my 2 cents worth:
You could have lost output from one rail by the sound of what you are saying. but the input cct may be fine.
I'd measure for:-
Dc at the output, should be close to 0 volts. ie across the speaker.
Also the VAS transistor voltage across the CE.
if you can measure the bias current would also be good to know if it still exists.
and post you findings.
also if you have an incircuit transistor tester it would come in hand.
but by the sound of it I would guess probably a driver and an ouput device have failed at the least, other than the 2 blown resistors.
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