Fender hot rod deville has weak output

[bigdrums925]

I've done all the usual testing (tested the tubes, input to the amp in jack, tapped the board and components, checked all the resistors & diodes on the amp board) and small repairs (resoldered both boards) and I'm completely stumped. Also tried pre amp out to another amp. From what I can tell the problem is on the amp section, (generated wave into the amp input results in same very low output. Checked the speakers DCR 3.8 ohms. There were many cracked solder joints on the amp board but built them up and made sure they flowed well. I also checked all the power supply voltages, and at the power tubes 6L6 GT's-- 3.2VAC ON PINS 2, 472 & 470.7 on the plates pin 3, 470 on both screen grids pin 4, -55 on both control grids, (yes it's running cold because I turned it down due to slight red plating) and 3.2 vac on both heaters, pin 7. I've also re-arranged and swapped the tubes all to no avail. No differences to report at all.
Any suggestions?

Here's the schematics

fender_hotrod_deville.pdf

[Enzo]

Are the speakers plugged into the MAIN speaker jack, and not the AUX or EXT speaker jack? VERY important.

[bigdrums925]

I also jumped the preamp out to the amp in. Still the same weak output. Also checked all the DC voltage test points on the schematics. And injected a 286mv 1k signal into the amp in, with an 8 ohm load connected measuring a pathetic <1volt output at the load. Help! One note: when I checked the diodes CR4, CR5 I got a 1.2 voltage drop. Is that normal for R3000 diodes?

[glebert]

Are the speakers plugged into the MAIN speaker jack, and not the AUX or EXT speaker jack? VERY important.

I always want to make that mistake with these amps. Is it so hard to actually label the jacks?

[bigdrums925]

Perhaps not but how do you tell? One of the jacks that's closer to the output tranny is more elaborate than the other and I assumed that was correct?

[bigdrums925]

Ya the other speaker jack is even lower output.

[Enzo]

Look on the sticker on the wall of the cab, the thing that shows the tubes. The jacks are identified there.

Look at your schematic. The MAIN speaker jack is the simpler of the two.

[bigdrums925]

Yes Enzo, that was it. Completely counter intuitive, but thank you!

[mozz]

Plate resistors on the phase inverter? Don't know if it was this model or not that had that problem.

[g1]

Yes Enzo, that was it. Completely counter intuitive, but thank you!

And running into a short would also be why you got red-plating (assuming it was when pushing signal rather than idling)