EL84 plate red-hot on Dynaco ST35

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EL84 plate red-hot on Dynaco ST35

Postby coolhandjjl » Tue Apr 26, 2016 1:37 pm

Hi-
I've a Dynaco St35 with original transformers, but rebuilt with Audio Regenesis boards and the Gillispie EFB Mod. I bought it already modded, but I re-tubbed it. I bought JJ driver tubes and Genalex Gold Lion re-issue EL84 power tubes bought as a matched quad. Not long ago, one channel sounded scratchy, and today, the plate in one of the power tubes turned red hot upon startup, so I shut 'er down right away. Before I put in new tube/s (I've an email message into Jim McShane already), are there any components on that board that should be checked that may have damaged that tube? All I have is a volt/ohm meter.
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Re: EL84 plate red-hot on Dynaco ST35

Postby coolhandjjl » Wed Apr 27, 2016 1:57 pm

Update: I tightened the pins and used same tube in same position, it didn't red plate anymore, but the tube still sits wiggly loose in it, and when touched (or barely breather on), makes static in that channel and bias voltage continues to climb. I'm guessing the socket pins are beyond tightening, so I'm looking at replacing the socket.
coolhandjjl
 
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Re: EL84 plate red-hot on Dynaco ST35

Postby paart » Wed Apr 27, 2016 5:24 pm

If the socket turns out to be the issue, then I would consider replacing all six, that is,
if you installed all the same brand when you did the modification. The same goes if any are the original Dynaco sockets. I’ve seen a number of crappy Chinese sockets over the past few years. The only sockets that I use now are Belton micalex sockets which are sold by a number of dealers, including Dynakit, Tube Depot, and Parts Express.
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Re: EL84 plate red-hot on Dynaco ST35

Postby coolhandjjl » Wed Apr 27, 2016 5:38 pm

Thanks for the tip! I've read others recommending those as well.
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