That's funny.
I am not sure about the 220pf grid load cap and the 3.3K ohm resistor. I don't think mine has that. Must be for the JB12, not the 150. The relay thing is different in mine also, the bias is switched on the relay contacts in the middle (and lower left side of relay).
The tube is good. After getting a few bugs worked out with my microphone, I get 100-125 watts all the time, mic was cutting out, didn't know it, and sometimes I'd only get 40-60 watts on peaks, and then other times it would jump up to 100+ watts. Wierd, pot in bottom of mic going bad or having a bad spot in it I guess, moved it around a little, works fine now.
Question though for those who know. I want to put a NEW EL34 or 6CA7 tube in this amp, and I have a JB200 also, it had 2 8417's I had to pull 1 for the JB150, the other I tested, it works but arcs inside everynow and then, some kind of flakes inside there...
So I want to get new tubes for both. What is needed to change from 8417 tubes to EL34/6CA7 tubes? Just bias voltage? if that?
Is there a difference in the EL34/6CA7 tubes advertised as for "audio" (AF) amplifiers and the standard tubes? I wouldn't really think so, more of a marketing gimmic it would seem, but maybe not?
Thanks again for all the help with this antique, I have gotten really good reports on it, had to turn my mic gain down to half, but once I did that it sounds really good, which that's all that matters, and 100 watts gets out quite good just by itself, really impressed at how far I can make contacts just on the JB150.
