Peavey session 500 Pedalsteel amp

[Pecco]

Hello for all! I am first time in this forum and I like to ask help to repairing this peavey amp.It was made 1980 europe model 220 Volts. I have checked main voltage is ok through fuses and thermal overload and main transformer is gives 70 Volts AC and 20 Volts AC without load (rectified to 52 VDC and 15 VDC). When I switch amp on ,only thing what happens is the green led on front panel is light on. Speaker is ok but no sound even hiss from any outputs . So can you help me about what to check next? Pecco From finland

[Enzo]

Hi Pecco, welcome.

If you don't already have them, contact Peavey and ask for the schematics.

First thing I would do is plug a spare cord from preamp out to power amp in jacks. If this restores the sound, the power amp jack needs service. Try the same test at the effects loop. And this amp has a volume pedal jack set, so check those.

I would also try to isolate the problem. PLug a signal into the input, then connect the preamp out jack to some other amp to see what output there is. And I would also try plugging a signal directly into the power amp in jack to see if that makes sound.

Check the connector where the speaker wires connect to the power amp board. Is ther continuity to the speakers from there? And very near that connector is a wire inductor on the board. Pull up on it to see if one end has broken free.

If your amp has the output transformer, try disconnecting it and connecting the speakers directly to the amp output. Any place there are those Molex conectors, there is always the possibility of a spread pin not making good contact.

This amp has the separate 500BH power amp board in it. If the power amp in makes no sound, then verify the +/-52V is getting to the power transistors. The preamp runs on +/-15V, so verify that those vokltages are getting to the ICs on the board.

[Pecco]

Hi Enzo and thanks for support , I have schematics to 400B/G board but not exactly right one ,board is dated 1978 and I found different component layout. I measured voltages to power transistors and 52 Volts is ok ,but two wires going to pwramp board (black and white) I found only 11 Volts and one resistor is burned , side by side the molex twopin connector. I cannot read colors of the resistor and dont know the number of this because brd layout is different, is it maybe 47 Ohms ?
Best Regards Pecco

[Enzo]

400B/G is not 500BH, and the preamp is not included anyway. Contact customer service at www.peavey.com and request the schematics.

[Pecco]

Hi Enzo , I,m really sorry i didnt inform You about this amp and schematics what I have. this amp has the driverboard 400B/G and I have the preamp ,pwramp schematics from Peavey . The problem is that the schematics that peavey send are not same year model. I am repairing this amp to my friend who is discussion on steelguitar forum .The 400B/G schematic which i download this side was the same we got from peavey. At the time the problem is 1978 400B/G board has different component layout vs. the schematic what we have. ps. forgive me the bad languaga I use We call it Finglish BR Pecco

[Pecco]

Thanks to all , We are now talking direct to Peavey because the amp service history is unknown and I found several problems with earlier repairs ( changed components dont match to schematics) . Br. Pecco