MC275 Gordon J. Gow no glow on 12AZ7 & no right channel sound

Hello All,

I am new with the forum and looking for some help on debug/fixing a problem that I am seeing on MC275 Gordon J. Gow(serial number E96??).

I got this amp from a good friend of mine who had this amp setting for almost 2 year in the original box.

I hook it up and power it up but no sound on the right speaker... I debugged it and find out that the second from the right 12AZ7 tube does not glow. I tired to switch it with other 12AZ7 which glow in the other socket but no-glow stays with the problematic socket...

I have not opened it up yet since I am sure there is something I can try to do some quick tests and fix... I do have a multimeter which I can use to check on a few connections.

Can someone tell me what I can do to debug further and possible cause and fix for the problem?

I live in Los Gatos, CA and if there is reputable shop near by, I am willing to try that as well.

Thank you.

Peter.

Clean the tube pins and sockets with DeOxit, Peter. If it was sitting, a mechanical problem is more likely than an electrical problem until doing things like metal-to-metal cleaning are completed.

You can easily confirm that the filaments in the tube is intact by checking resistance between pins 4 and 9 for one of the triodes and pins 5 and 9 for the other triode.

I've not had the good fortune to see inside one of the GG amps but the next step is to measure the voltage on the same pins of the offending socket to determine if there really is voltage being presented to the socket's pins.

As for a place locally, Surtech and L&M are frequently mentioned in the SF Bay area. Here's a past AK thread on the topic.

Cheers,

David

Thank you very much for your reply, David.

I will do the "DeOxit" cleaning first - this shouldn't be too hard and also measure the voltage on the Pin 4&9 and 5&9(I am guessing that the pin 9 is the ground?)on the other working socket and this non-working socket to compare.

I will report back the result in a few days.

Thanks again!!!

Pin 9 is the common side of both filaments. Google '12AZ7 pinout' for details.

Cheers,

David