Peavey Classic 30 - no output

[Raybob Bowman]

I have a 90's Peavey Classic 30 with no sound/output/voltage at the speaker. All the tubes light up/warm up but no output. I have a schematic for the amp but it isn't showing any voltages that I could be looking for on it, that I can see. Any ideas on what to look for?

Raybob

[Eric West]

Try some different preamp tubes. They can glow and still be bad. Happened on my Cl50.



EJL

[Raybob Bowman]

Thanks for the suggestion Eric, I just tried three brand new 12AX7s from China but still no sound or voltage at speaker.

Raybob

[John Billings]

Rectifier tube?

[Raybob Bowman]

Don't see a rectifier tube but there are diode bridges on the schematic. I suppose I can check the diodes but I would think if the bridge rectifiers were out, I wouldn't have power at the tubes.

Raybob

[John Billings]

Yeah, but the heaters might still work? Donno.

[Ken Fox]

You have several voltage considerations at the power tubes:

6.3 VAC heaters (if you see them glow that's OK)

Plate voltage 332 VDC

Screen voltages 327 VDC (output volume dead if missing)

bias voltage -14VDC

If you must ask, it is likely you should not be inside this amp to start with, no offense intended.

This is a difficult amp to work on due to the way they wired three circuit boards together with jumper wires. I refuse to work on these amps if it goes deeper than a tube change out, period!

I would send it to the Peavey Service Center in Meridian and let them take it apart and work on it!!

[Raybob Bowman]

Thanks for the info Ken. I understand your concern especially since what just happened to you. I know my way inside amps but haven't really been in one for about three years and needed a refresher. Since John's suggestion, I checked the diodes and found the 4 on the bias voltage all pass voltage both ways. Looks like the cause was a broken lead where two of the three boards hinge.

This amp is a nightmare to work on but I'm doing it for a good friend that bought the amp from me 10 years ago.

Raybob

[Ken Fox]

Those wires where the boards are hinged together are a big problem for sure.

Just such a bad design to work on, as you can see. A great sounding amp for sure, but a tech's nightmare!!

[John Billings]

Kinda off topic, but,,,,
I bought a Delta Blues 15" to play my baritone guitar through The transformers were really small! My tech and I replaced the power xformer with a much larger Hammond, and the output xformer with one I got from Dr. Z. What a huge difference! Tremendous amp. But my tech was cursin' his way through the connections between the boards.

[Jim Sliff]

Same as Ken - I won't work on any Peavey tube amps for the same reason. Unlike Fenders, Marshalls, Traynors, and a lot of the newer amps (even PCB's) they were NOT designed with "easy servicing" in mind, which was one of Leo Fender's Mantras, and one Jim Marshall and Ken Bran picked up from across the water.

[Mike Brown]

Call our technical assistance line at 1-877-732-8391, ext. 1420 and/or ext.1295.
Mike Brown
Peavey USA

[Raybob Bowman]

I replaced the 4 diodes but they weren't bad to begin with, evidently. It seems you have to pull them from the board to test because the circuit let it look like current could flow in reverse on the diodes. I patched the break in the hinge wires and an open connection at a power resistor and everything works fine now. What really took more patience than Job was lining up the speed nuts on the chassis just right so all eight screws would line up putting it all back together.

I'm telling my friend if it goes bad again, just get another amp on eBay.

Raybob