Fender Hotrod Deluxe poweramp distorting

[edge59]

Hi, I have a Hotrod Deluxe that has a bad farty distortion and it seems to be coming from the power amp (this is one of 2 HRD that are used at the Shasta Blues Society) The other amp sounds great! I tried plugging into the power amp in and it seems to be where the problem is as I have done this with both amps. And they have both been retubed and recapped, all voltages seem fine or are very close to the schematic. it sounds like its starving voltage, the sound you would get as if you hit a note and turn off the amp, just right as the voltage starts to drop, I swapped out PI .1uf caps and .022uf PI input cap, still that bad distortion.. Has anyone come across this? I even tried a different opamp in the effects loop. Resistor values seem to be in tolerance as well.... Any takers? Please? I thought it might be the output tranny as I get a slight different resistance reading from the brown to red and blue to red (86 and 111) Can that be a problem or is that tolerable?
thanks!
Edge59

[Dave Curtis, dB AudioTech]

Is your speaker plugged into the extension speaker jack? That's a no-no.

[6267]

Filter caps in power supply maybe? I don't know about the transformer...they "always never" match between legs, but I'm not sure how far off is too far off...is the other deluxe's opt giving similar DCR?

[Enzo]

All voltages are fine? Just what voltages do we mean? Only the ones on the drawing?

Don't just swap parts as a guess, get systematic in your troubleshooting.

Look at the power tube sockets again - unplug the amp first. CLosely, are there any cracks in the solder on any of the pins where the socket solders to the circuit board? WOuldn't hurt to reflow them.

Power up.

Look at the power tubes. Is there full B+ voltage on both pins 3 AND 4 on every power tube? Got the same bias voltage on both sides at pin 5?

Look now to the phase inverter tube - the small tube closest to the power tubes. Is there B+ voltage on BOTH pins 1 and 6? About the same voltage? I don;t know what, 200v give or take - not zero, not 400. Fender phase inverters like to eat plate load resistors. A missing plate voltage indicates an open resistor.

[edge59]

Hi guys and gals, I found the problem after doing most of your suggestions, I had purchased a Quad of GT 6L6 CHP blackplates and 2 sets of preamp tubes: 2-Tung-Sol 12ax7's, 2- Penta Labs Chinese 12ax7's, and 2-Electro-Harmonix 12ax7's all balanced pairs from Doug'stubes.com.
I was in a pinch trying to get the amps ready for last weekends Blues festival. Anyway today after checking every part, voltage, and butt crack, I found the problem to be bad solder on the 6L6 CHP pins, so I relowed the pins with some fresh solder and reinstalled them and it worked, lol! Anyway, thank you all for your suggestions! It did sound like 1/2 power and like it does when one power tube is missing, ola!
Edge59