Jet City 100

[pnut5150]

Amp was red plating, checked everything in the bias circuit and it all checked good..choke started smoking today..if I'm looking at the schematic right the choke can cause red plating..right? Checked all screens and plates they are all dead on where they should be..

[g1]

What schematic? The one you have and we don't?

[pnut5150]

Oh yea this might help lol

[g1]

I'm thinking the opposite could also be true, redplating tube causing choke to smoke. Have you tried other power tubes? First verify you have good bias voltage at power tube sockets.

[pnut5150]

Yea should have mentioned that, but I have tried other power tubes, these are about a week old, bias wheel was bad, replaced it and used amp all week, then started redplating all at once. With my bias probe I am showing 50ma when I first turn it on, then it climbs to 4.20 and climbs..tubes are bbq by that time.

[g1]

Then get the bias voltage sorted out before installing any power tubes.

[pnut5150]

I'll see what it is without tubes when I get back home, when choke was smoking I quit

[pnut5150]

With all the tubes pulled I am getting no bias reading with my bias probe..all of the 470 ohm resistors have 500+v on them, however the 2k2 resistors all read -39.00v. R13 & 14 have -39.00v C10 & C11 have 500+v on one + side as well as R9 & R10. I know there is something I am overlooking..R11 is -39.96v R18 (end to bias wheel) is -39.97 and the other end is -000.0mv
Tube sockets
Pin 1 -000.0mv
Pin2 002.2mv
Pin3 538v
Pin4 538v
Pin5 -38.85v
Pin6 537v
Pin7 290mv
Pin8 -000.7mv

[52 Bill]

With all the tubes pulled I am getting no bias reading with my bias probe..

That's normal. The tube must be installed to draw any current.

You have -39 volts on pin 5, can it be adjusted any higher or lower?

[J M Fahey]

Oh yea this might help lol
[ATTACH=CONFIG]36086[/ATTACH]

Thanks bit it's almost unreadable, both fuzzy and small ... and it's only the power amp, while the magic is usually on the preamp.

Can you please post the full .PDF , as you received it?
Thanks

[pnut5150]

No it can't be adjusted, but I just checked one tube..v7&v8 does not have the 500+v on pin 6

[pnut5150]

Let me see if I can find one

[pnut5150]

http://https://www.google.com/search...D7URhL04_HM%3A

[pnut5150]

pre and pwr amp schematic