2-el84 cathode biased amp.

[MarkT]

2-el84 cathode biased amp.
1 of the tubes is red-plating slightly. Can be seen with the room lights off.
I switched the tubes around and the red-plate occurs on only the one socket.
I'm thinking its a dirty/oxidy/loose socket or the 110 ohm grid resistor going bad. I'm going to clean the socket with a contact clean. Let it dry real good and go from there.
Cheers.
MarkT

[dtcurare]

I may have that on a new 18 tmb build.  Its V5 on mine.

[AmberB]

My suggestion would be to use a common cathode resistor for both EL-84s.  That way, you know that you have a specific resistance for both tubes.

[passaloutre]

What’s the measured dissipation?

[sluckey]

My suggestion would be to use a common cathode resistor for both EL-84s.  That way, you know that you have a specific resistance for both tubes.

Did you mean to say "use a separate cathode resistor for each EL84?