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Peavey F800G Falling apart, Motorboating
This is the same one as I posted before. Sucks. I got the amp to pass signal again and was able to get everything functioning less the tremolo with a custom made footswitch. CST came by, loved it, wanted the tremolo to work as well. Went back through the preamp and in the process, all of the thread wire started breaking down, fray and or break off from being moved too much (input to power section, reverb RCA's, input leads to preamp section, etc. Then, no signal again. I can trace signal to the volume pot, but no overdrive. There's also a new buddy of consistent motorboating noise coming from the speakers with or without signal applied... Cements replaced, checked output transistors with a diode test and they all check out. I also replaced the 22Ohm resistors (1watt) on the power section too. No luck. Any suggestions? Thanks in advance.
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Found additional broken wire at one of the output transistors. Motorboating has stopped. Went to test and voltage to preamp was really low. Tried to bring back to 24VDC but it won't go past 11VDC before decending again... -
A *beast* of an amp.
Would love to hear it with 2 x 4 ohm cabinets, full tilt ...... from a distance.
Check that those voltages posted on the 24V regulator are still there.
The lowest transistor is used as a Zener (it was cheaper way back then); if you are far from the stated 9V there replace it with a 9V Zener (I think the normalized value is 9.1V or thereabouts) or you'll never be able to adjust properly.
Good luck.Juan Manuel FaheyComment
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Nice! So the SPS953's were both malfunctioning. Replaced and got voltages back, but so is the motorboating...Comment
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If you disconnect the preamp from the power amp does the motor boating go away.
If you inject a signal straight into the power amp, does the power amp work properly.
If so, inject a signal into the input of the preamp & follow it through the signal path. Where does it start to go screwy. Thats the part that needs to be fixed.Comment
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