Fender Blues DeVille 4x10 Re-Issue Problem

[Zippy]

I plugged in a chord,and there's a major loss in volume.

I don't get this. If you have no cord plugged in, you should have no volume. How can you get a "major loss in volume" by plugging in an instrument?

[billyz]

Test for bias voltage at the power tube pins 5. I believe the 220k grid load resistors are on the same board as the power tubes . So the ribbon is probably not your problem if you have bias voltage at the tube pin. Of the all of these I have worked on never found a bad coupling cap . So leaky cap is improbable too. Swap the tubes if red plate follows the tube you know the drill. Get a good set of tubes.

[soupbone]

Test for bias voltage at the power tube pins 5. I believe the 220k grid load resistors are on the same board as the power tubes . So the ribbon is probably not your problem if you have bias voltage at the tube pin. Of the all of these I have worked on never found a bad coupling cap . So leaky cap is improbable too. Swap the tubes if red plate follows the tube you know the drill. Get a good set of tubes.

Excellent!Thanks for the info Biily Z.!

[JazzGuitarGimp]

I plugged in a chord,and there's a major loss in volume.

I don't get this. If you have no cord plugged in, you should have no volume. How can you get a "major loss in volume" by plugging in an instrument?

Zippy, I can't tell if you're being sarcastic or serious.
If serious, I think what the OP meant is that the amp isn't as loud as expected.
If sarcastic, I say The last 'chord' I plugged in was an Ab13#11

[soupbone]

I plugged in a chord,and there's a major loss in volume.

I don't get this. If you have no cord plugged in, you should have no volume. How can you get a "major loss in volume" by plugging in an instrument?

Zippy, I can't tell if you're being sarcastic or serious.
If serious, I think what the OP meant is that the amp isn't as loud as expected.
If sarcastic, I say The last 'chord' I plugged in was an Ab13#11

Funny.

[Stevem]

Alot of those cheap 2 cent bias pots in those amps go intermitant( like 80% of the time once a tube red plates) so I would get a normal size 1/2 watt pot, hard wire it in with long enough leads to let you silicone glue it down some where.
There is plenty of room to drill a mounting hole for the new pot over by the speakers jacks and thats what I mostly do though.
Also be sure to go over all the solder connections on the tube sockets with leaded type solder, (not no lead solder) as you will likly find atleast on the output tubes rings around the pin solder joints which means they are going bad.

[Zippy]

I plugged in a chord,and there's a major loss in volume.

I don't get this. If you have no cord plugged in, you should have no volume. How can you get a "major loss in volume" by plugging in an instrument?

Zippy, I can't tell if you're being sarcastic or serious.

Thanks, JGG - my bad. I'm a very literal person - when I troubleshoot, I look for causality. This really did trip me up. I see now what the OP may have meant, when you put it that way.

[groovtubin]

I don't get this. If you have no cord plugged in, you should have no volume. How can you get a "major loss in volume" by plugging in an instrument?

Zippy, I can't tell if you're being sarcastic or serious.
If serious, I think what the OP meant is that the amp isn't as loud as expected.
If sarcastic, I say The last 'chord' I plugged in was an Ab13#11

Funny.

Been modding/repairing these amps since 1998, the solder joints RIGHT at the pilot lit under shrink wrap, will go COLD, n cause ALL kinds of prob`s, loss of volume, popping, etc...talk @ circuit constants! The low voltage hi current power supply sees all that crap goin on n DON`T like it! lol! I`ve seen these amps change channel all on their own due to that one prob at pilot light!

jim@Omegaamps

[Stevem]

It may very well be that your problem is a bad output transformer, also note that the bias adjust trim pot on these amps and the smaller Deluxe model drift often,and or fail and go open.
If your negative bias voltage on pin 5 of each tube is the same then there is a chance that both tubes are good and you have a bad solder connection on that tube socket.
Check also for voltage on pin 4.