Peavey Delta Blues Red Plating

[ca7922303]

Two(2) of the four(4) EL84s are red plating.. Turned on for about ten(10) minutes and V7 and V8 slowly increased red plating until I turned off. V7 was noisy when touched. None of other tubes including 12AX7s were noisy. Haven't taken any reading yet.

[g1]

Does it have 8 tubes? Schematic attached has only 7. Check for bias voltage at pin9 of all power tubes.

[Jon Snell]

I would check the valves by swopping pairs over 4/5 - 6/7.
If the issue follows the valves, replace all four EL84s. If the issue stays with the valve holders, replace C32 & C35 both are 22n 400v (0.022uF)

[ca7922303]

Does it have 8 tubes? Schematic attached has only 7. Check for bias voltage at pin9 of all power tubes.

Yeah, meant V6/7 red plating. Swapped tubes in pairs, red plating followed the tubes, so replaced two that were red plating, now good. Will check pin #9 of all power tubes momentarily. Thanks.

[g1]

Agree with Jon, particularly with EL84's it is best to replace all four. They have fairly short lives compared to other power tubes, and if some are bad, the others are probably old enough that they are on the way out anyway.

[ca7922303]

Agree with Jon, particularly with EL84's it is best to replace all four. They have fairly short lives compared to other power tubes, and if some are bad, the others are probably old enough that they are on the way out anyway.

Will do. Thanks.

[ca7922303]

I would check the valves by swopping pairs over 4/5 - 6/7.
If the issue follows the valves, replace all four EL84s. If the issue stays with the valve holders, replace C32 & C35 both are 22n 400v (0.022uF)

Replaced all four (4) EL84S and red plating is gone. Thanks for your help.