Peavey Deuce problems... Need Help!!!

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cannadaincowboy
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Peavey Deuce problems... Need Help!!!

Post by cannadaincowboy » Mon Feb 06, 2023 2:59 pm

I bought a Deuce for 100.00 and replaced the speakers With G12T-75. I replaced the tubes with new ones and still don't have full power. I can turn the master to 10 with the Pre around 3/4 in the normal input. It's loud but not as loud as it should be. I connected the Eurotube Bias probe to one of the tube sockets and into my fluke. I wanted to see where the plate current is and should be around 38 to 42 milliamps at 70%. With a 2nd Fluke meter connected My plate voltage is 508VDC PIN #3. So with everything connected I was warming the tubes and had my voltage reading on pin 3 at 508V. I then switched the lead to pin 4 and turned on the standby switch. Voltage was 504V on the meter and PIN#5 is 55V. then I looked at the milliamps it flashed to 31MA then it started dropping and settled on 0.6 milliamps. Putting my hand about 2 in from the tubes I couldn't hold my hand there for more than 6 seconds. I am going to replace the high voltage transistors in the power circuit I bought the MJE3439 transistors. Hopefully, that fixes the issue. I've never seen this happen in my Hiwatt and wondering if anyone had a similar problem. Or is there anything else I'm missing? The filter Capaciters all look like they have been replaced.
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dak
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Re: Peavey Deuce problems... Need Help!!!

Post by dak » Mon Feb 06, 2023 4:55 pm

In the image called deuce7.jpg on the upper right there is a resistor which has burnt the PCB below: apparently it is running hotter than it should. To its lower left (skipping one) there is a ceramic capacitor with a burned spot on it.

I am not sure about the plentiful brown goo everywhere. If it's intentionally there, I have problems guessing its purpose.

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Pappy B
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Re: Peavey Deuce problems... Need Help!!!

Post by Pappy B » Mon Feb 06, 2023 9:34 pm

the brown stuff is just glue to keep parts from moving.

I wouldn't throw any more parts at it until the circuit board is pulled from the chassis and the traces inspected. You may have to repair some traces. That large resistor should get hot but not to the point of burning the board. Another resistor may have gone out of spec or the electrolytic capacitors may have failed. I always recap amps that old. And usually replace the power resistors.
The more I learn the more I realize how much I don't know.

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j0nsnell
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Re: Peavey Deuce problems... Need Help!!!

Post by j0nsnell » Tue Feb 07, 2023 2:04 am

Why replace the phase splitter transistors when they are AC coupled and have no bearing on the quiescent current draw of the output valves.
You are barking up the wrong tree!
Check the bias -ve voltage for stability and the grid coupling capacitors to the output valves for DC leakage.

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