Tube Socket Or Not Tube Socket - Ampeg Reverberocket 212

[marcumh]

Reverberocket Main PCB Schematics (27801HK_).pdf

Good evening gentleman,

I am working on a Reverberocket R-212 that has a tube redplating. While looking at voltages I noticed I am getting ~20-30vdc at pin 6 on the redplating tube. I pulled the tube socket and voltage at the points are good (no dc @ pin 6). The socket is in physically good condition, there is no detectable continuity between any of the sockets. I would have popped another in, but I'll have to order it in; so I figured I'd talk to you fellows in the mean time. Just wondering if any one has experienced this with a tube socket (if that is the problem)?

I should add. That when the tube socket is in; my bias voltage is down from ~-40vdc on both sockets to ~38vdc on the "non-bad" socket and ~33vdc on the "bad" socket. When the "bad" socket is out, both sides are stable at ~-40vdc.

Have a good evening.

[soundguruman]

[ATTACH=CONFIG]22021[/ATTACH]

Good evening gentleman,

I am working on a Reverberocket R-212 that has a tube redplating. While looking at voltages I noticed I am getting ~20-30vdc at pin 6 on the redplating tube. I pulled the tube socket and voltage at the points are good (no dc @ pin 6). The socket is in physically good condition, there is no detectable continuity between any of the sockets. I would have popped another in, but I'll have to order it in; so I figured I'd talk to you fellows in the mean time. Just wondering if any one has experienced this with a tube socket (if that is the problem)?

I should add. That when the tube socket is in; my bias voltage is down from ~-40vdc on both sockets to ~38vdc on the "non-bad" socket and ~33vdc on the "bad" socket. When the "bad" socket is out, both sides are stable at ~-40vdc.

Have a good evening.

A. Clean the pins on the tube with scotch bright polish pad. Make sure the pins are bright and clean...
B. Spraying cleaner into sockets is just about worthless. Cleaning does not fix worn out plating.
The plating wears out on the socket, you may read a voltage, but the voltage may not be reaching the actual tube pin.
OR you may actually have a bad tube, or the plating on the tube pin may be oxidized.
When the contacts become oxidized, it can burn the plating, inside the socket. Then the bias may fail, etc...
Well, if it drops the voltage when the socket is "in," there may be burning through the insulation on the socket...
This burning forms a carbon track. The carbon is just like an extra resistor in the circuit.

*Once a carbon track forms (it may be invisible), you cannot "clean" it off. The socket MUST be replaced. There is no easy way to fix it permanently.
** Cleaning sockets with spray cleaner is a joke. The cleaner can cause MORE arcing and burning. There isn't any cleaner that is rated for that temperature and voltage.

Although spray cleaner on a socket may temporarily fix a problem, it's going to re-occur. Do not depend on cleaners to fix worn out plating, or carbon traces in the socket body.
The bias SHOULD be on pin 5. If you read voltage on pin 6, you have a defective insulator in the socket!

[Bruce / Mission Amps]

Since you should not have a positive voltage on the grid, my guess is a just bad power tube too, and probably nothing else.
Well, that is assuming it is a 7591A.

[marcumh]

Thanks guys. I should have mentioned that I did try different tubes with the same result. I have a replacement socket OTW.

[Jazz P Bass]

Have you ruled out a leaky coupling cap? (C21 or C22)

[marcumh]

Have you ruled out a leaky coupling cap? (C21 or C22)

I have not. Since the issue is only present if the tube socket is soldered in (with or without a tube in place), I've pretty well had blinders on about it being the tube socket. Of course I'm open to the likely hood that I am

[marcumh]

Just to put this one to bed; the problem did turn out to be the tube socket. Thanks for the replies.