Pignose G40V?

[reddinis]

I'm going thorugh trouble shooting charts and such right now, but wanted to post this now to maybe make things quicker.

Basically, I was playing my amp this morning, it was working fine. I turned it off, walked 50 yards home with it and set it down in the living room.

Just now, I fire it up and there is only a loud hum - no sound from the guitar coming through at all.

Edit: The volume and master volume both affect the hum, it can be turned down all the way?

Any help appreciated. Thanks.

[reddinis]

When I turn it on with guitar plugged in, if I hit a string, the hum dies down briefly, each time I hit a string, but then comes right back.

When I power the amp down, I can hear the voltage draining through the speaker. I turn it off and the hum fades slowly.

[reddinis]

I had put a push/ pull pot in the negative feedback loop to change resistance and to be able to take it completely out of the circuit.

I have now put the NFB loop back to stock, and now there is no change in the hum when I hit a string.

[reddinis]

Did I Blow My OT?

The resistance on the primary side looks to be good. With no power on (voltage drained) all of the secondary leads are shorted, which is normal? Is that right?

I haven't done the test for the secondary windings where I would put half of 6.3V onto one of the primary leads, yet.

But, does it sound like my OT could be bad?

I've never had a problem with this amp. I put in a new OT (old one worked fine) and did the NFB mod. It worked fine this morning. Tried to fire it up later today and it's not working. I've been messing with it for a while now haven't figured anything out.

Any help appreciated. Thanks.

[Euthymia]

Tried swapping the preamp tubes for known good?

[reddinis]

Thanks, Euthymia. What happened was, I switched the NFB loop in while powered up (big pop). It looks like I killed the capacitors around the phase inverter. I didn't see the phase inverter glowing at first because of the tube shield.

I was in a state of panic. I spent a lot of money on this OT. I'll be able to get caps tomorrow and hopefully it's just the caps. As far as I can tell right now, everything else is fine.

Also, I've never had a problem with this amp, had it for a long time. I only changed the OT to improve tone.

[Euthymia]

While you have the the PI tube out check the values of all the resistors associated with it. If you nuked the tube, it may have crisped one or more of them.