50 watt jmp

[tvjr]

Hi Chuck,happy thanksgiving. Hope all is well.I got another 12ax7 brand new and plugged it in .No change,still speaking volume. I got pissy and retouched all the tube connector pins with my soldering iron just to make sure there o.k. Sprayed all the pins on the tubes and worked them in and out for awhile, no change. then got really nervy and lifted the entire board to look underneath and all looked o.k. No broken joints or anything visible. Put it all back together and nothing has changed it's still the same, what a suprise! At least i didn't break anything else.By the way ,that cap second from the end of the board that's not on your board is 330uf 6.3v if that helps. Thanks for your time and effort,it's turkey day so just relax and take it easy. TVJR

[acorkos]

check the dc voltage on pin 4 of each power tube. and meter the 1k screen resistors on those pins, make sure they are up to spec.

[tvjr]

jmp 50 watt 76

Thanks for responding,believe it or not i managed to get this thing working. Like hitting the lottery i touched pins 1 and 6 onV3 with the mutimeter ,and presto i had good volume. So i went to the board and put the meter across the 100k resistor and the same thing happened. So i soldered in a new 100k and whamo just like new.Holy crap,can't believe it,it works. I would like to thank all who helped me get to this point,the forum works. thanks again, TVJR

[Jazz P Bass]

Ideally in a static test you would read the Vdc of the preamp tubes at pin#1 & pin#3, pin#6 & pin#8.
That reading will tell whether or not the circuit is conducting or not.

This is why I stated this.
If you would have measured the dc voltages, to ground, of all the 12AX7s at Pin 1 & then Pin 3 & Pin 6 & Pin 8 you would have quickly verified that Tube #3 was not conducting.
Hence your bad 100K load resistor.

[tvjr]

jmp 50 watt 76

Dear Jazz, you were right ,guess i wasn't smart enough to listen.Next time i'll pay more attention. thanks ,getting smarter a little at a time. TVJR

[Chuck H]

I actually did see it in your second post. But I guess I didn't read the post carefully enough because though I did see the high plate volts I misinterpreted it as V1. That's why I was looking for a cathode fault on V1.

Glad you fixed it.