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hello, i have the amp in the title, had it for years, and now all the sudden when i play through it, it goes to this loud humm, beat on it, works for a bit, then does it again, ive tore it appart many times, resoldered all connections, and nothing works, i found if you grab the transformer and wiggle it around it'll work while your doing that, but as soon as you let go it goes back to the humm? im pretty good with working on electronics, but this has me baffled. ive tightened all the srews, cleaned all the connections and all that to, i dont know where to go on it now?
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Isolate the problem.
Flex the main filter caps. Does that make any difference?
Look at the main voltages for the power amp. I don;t know what they are, but I'd guess 30-40 volts one each polarity. Are both about the same? When it hums, does one drop a lot lower?
Then look at the low voltage rails - probably +/-15VDC for the op amps. Again, are they both about the same and up to voltage?
use a chopstick or other insulated thing and poke each copmponent on th board. Find any that affect the noise?Education is what you're left with after you have forgotten what you have learned. -
hi Enzo, thanks for the reply, ive actually done most of that, i havent tested any voltages though, ive tried to isolate it, but nothing really seems to affect it. the one thing that does, is on the effects loop, external speaker and foot switch jacks, i move them around, and that works sometimes for a little while. ive even disconnected the reverb rca's, that doesnt do anything at all. im stumped, it also seems like vibration has a lil to do with it to? could something overheating cause this? when it 1st started this, it was almost like after it warmed up for a while it would stop doing it, and i could use it for a long time, but eventually it would do it again. please excuse my ignorance lol, im not familiar with what capacitors do and transistors and all that, i know how to replace the parts that are bad, but i dont know what all the lil parts do, or what the voltages are and stuff. i do appreciate your help though!Comment
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If it respnds to beating, then there is a loose connection.
You must be meticulous and probe each and every part - give them a little shove.
I would power down and remove the main board. Look at the solder under EVERY one of those rectangular cement power resistors. try specifically wiggling them.
Your main filter caps are the largest cylindrical things on the board.Education is what you're left with after you have forgotten what you have learned.Comment
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