Bad Tube? Bad Joint?

[Ag_Nathus]

Hi everyone, I have a 100w plexi kit and am now getting 20V DC on pin 8 of V6! All the other pin 8s on the other power tubes are behaving at 34mV. Is this most likely a bad tube or a bad connection on or off the board? Any help on where to start would be awesome! I am including a picture of the chassis, maybe someone could point out the region to start in.

Thanks!

AG

[IMG=http://img829.imageshack.us/img829/4179/dsc04141jc.jpg][/IMG]

[toner]

Swap tubes around to see if it's the tube or socket.

If it's the socket, the most likely causes are:
- bad 1 ohm resistor (check resistance with meter [power off])
- bad/loose ground connection on that resistor's ground lug

It could also be the solder joint on pin 8, depending on where you measured the voltage (on the pin directly or on the resistor leg that connects to it).

[Ag_Nathus]

Thanks for the tip! It appears to be a bad resistor since it is showing infinity on my meter, where the other resistors are all 1. something. Since the amp is biased to the other tubes, and I dropped it a touch to be safe, is it still safe to play until I can replace the resistor? They are only used for biasing anyway, right?

Thank you for your help!

AG

[toner]

...is it still safe to play until I can replace the resistor? They are only used for biasing anyway, right?

No! Do NOT run the amp that way.

I'm not sure about damage to the amp but it's possible. You should replace the bad resistor with a wire to ground until you get a new resistor. The tube won't work correctly.

Normally the cathode (pin 8 ) is grounded. Leaving an open resistor (infinite resistance) there will break the ground connection.

[Ag_Nathus]

Ahahaha! Thanks, my bad.
Thank you for your help!
AG