Question from struggling newbie dumb guy.

[sdorer]

I'm trying to make an octal tube Gibson ga30 and having sa heck of a time. I'm using an old hammond organ amp with a field coil speaker' It has a paraphrase phase inverter. With this is it expected that one of the 6v6 plates is running 40 volts different than the other. Between the field coil speaker and the sj7 input tube I'm really struggling. Also if anyone has the pin voltages for a ga30, early octal version, I would appreciate it.

[alvarezh]

I see octals for the rectifier and power tubes, if that what you mean, then see if this helps:

http://www.gibson.com/Files/schematics/ga-30b.gif

All the best.

[Structo]

Are you still using the field coil speaker?

I believe they used the field coil as the choke for the power supply, correct?

I have a 12ax7 version with voltages but that may not help you.

Since this is a cathode biased amp I would suspect the tube that us pulling less current to be dying.

If you want to use as permanent magnet speaker you may be able to sub in a 10 watt resistor 300-500 ohm or use a choke coil.