Pls help troubleshooting amp!!

[redshark]

A friend gave me an amp to fix. He told me someone turned on the amp without a load and left it on. So OT and power tubes were gone. Replaced OT and power tubes and the amp plays but power tubes redplating like hell and smell like they r cooking. Checked plate voltage and is low 330 vdc's and when put probes to read current is too high...338mA!!! what could be wrong?
thanks in advance!!

[benoit]

I would probably look for burned resistors and/or somewhere where an arc caused a connection between two power tube pins.

[Structo]

More information needed.

What is this amp based on model wise?

Is it cathode biased or fixed bias?

What are the power tubes?

Measure the DC voltage at Pins 5 of each tube and report back.

[redshark]

Thanks Tom!! marshall 50 watt head, 4 input, el34 looks like someone added a master volume....I'm testing the amp with sovteks 5881 (don't wanna damage brand new jjel34's) let me take voltage pin 5, fixed bias, brb...

[redshark]

weird readings on pin5 -0.038vdc and -0.430vdc

[labb]

I would take a close look at the biasing circuit.

[Bob-I]

weird readings on pin5 -0.038vdc and -0.430vdc

There's your problem. It should be more like -42. Bias supplyu took a hit as well.

[redshark]

I'm starting to think the PT is bad, measured all components in the bias circuit and individually they test fine, but voltage is only -4vdc. I went down to the PT, trying to read AC and is low, 2hundred something, I think I should be getting like 380vAC before rectifier diodes. More ideas?

[Structo]

I would disconnect the HT leads and measure the unrectified voltage.
You may have one or more shorted diodes, unless it has a bridge rectifier.

[redshark]

One more reason to hate PCB's!!!!
All this time checking stuff, component by component, and all the problem was that one of the traces of the PCB in the bias circuit wasn't conducting, so I never had bias...One more lesson to learn!! just soldered some wire and problem fixed... what a waste of time!!