Peavey Ultra Plus 120W Tube Amp No sound output

[Kegfish]

I haven't used this amp for ages, it's been in the box for years but after I completely dusted inside and out and went to use it today - no sound output.

After I bought it I sent it to Peavey and they serviced and re-tubed it. I don't recall if I have used it since though I surely would have tested it upon return so I'm presuming it worked at least once.

The power tubes appear dark, I'm presuming the heaters aren't getting power but all of the lights and indicators are working. I was wondering if anyone had taken one of these apart before and where I would find the fuses, I don't see any external fuse locations? Are the feet screws what hold the amp in the cabinet?

I appreciate any help!
Kegfish

[Enzo]

I think so, I think it is like the 5150. So just unscrew a rubber foot. if it has a ling machine screw, then that is the case.


Yes, there are fuses inside the amp.

The voltages the amp runs on can KILL YOU, so be very careful inside.

There will be wires over to the power tube socket board, look close at the connectors. DO any of the pins or wires look brown or burnt?

[Kegfish]

Thanks, I'll get started, I didn't want to take anything apart until I was sure the foot screws were right. I was worried I would loosen something inside by mistake. I've done some amp work before but its been forever. I'll post back after I have it apart. It kills me it looks perfect [externally] but not a peep. Thanks again for the help.
Kegfish

[Kegfish]

Hi Enzo, I removed the amp from the cabinet, the boards and area are pristine, I can't see any discoloration, no dirt/dust, and all connectors and ribbon connectors are in place and seem tight. There are 5 fuses; one I believe to be the main, [it is alone at the end of the enclosure, outboard of the power switch, and the wires are going to the power switch] it is a charcoal colored 5A 250V [ceramic?] has a label next to it warning "for safety replace with same size and type fuse" the label calls for 5A/250V and the 5 is hand written but the 250V is preprinted with the label. The other 4 are on the circuit board; 3 are clear with spring type wire visible and all appear intact though I can't read the sizes. The fourth is also on the circuit board but I can't see through, it is white, [ceramic?]. All the power and preamp tubes also look pristine. The only thing I could see that seemed odd was on top of one of the transformers, nearest the power switch end, has a copper plate on top of the transformer but the other transformer, on the input jacks end, has no copper plate though there appears to be little blotches of clear ameba shaped dried blotches, [possible hot glue residue?]. I was wondering if maybe it should have a copper plate as well? Could it need to ground to the reverb unit above it for some reason? I didn't notice if the transformer with the plate was in contact with the reverb unit when I took it apart.

At any rate I'd really appreciate any help or ideas as I really don't know what to check next.
Thanks Kegfish

[Enzo]

The amp left the factory working, so let's not take up our time trying to look for original parts beiing wrong. The transformers are fine. Glops of potting tar are fine, the copper band is a shield on the power transformer.

The only REAL test of a fuse is to remove it from its clip and measure it with a meter, especially the ceramic ones you cannot see into. And in fact, if your heaters are not lighting up, then that white one is the probable suspect. don't measure it still in its clip, pull it first.


The main fuse must be OK if some functions of the amp come on.

[Kegfish]

I did get the white fuse out, it is a 10A and it continuity checks good. Should I measure it for a specific value? The others were going to be harder to get out and I didn't want to risk breaking one since they appeared intact. I thought the same about the grey one. Also since I wrote last I've been poking around more and from a different angle I spotted a discolored spot on one of the ribbon connectors. So I imagine I'm stuck with a trip to the shop after all; unless you have any other ideas. Do you think it could make the discoloration and not blow one of the fuses?

[Enzo]

Fuse checking is for continuity, not a specific resistance.

yes, a connector pin can easily burn up without taking a fuse.

If fuses are OK but no tube heaters glowing, then we follow the 6v heater current from transformer to tube socket to find where it goes missing.

[Kegfish]

Good morning, I was afraid you'd say something along those lines. I have a DMM but not a huge amount of experience actually measuring voltages; as where and how to get to the points. I have the chassis removed and unhooked the discolored end of the ribbon connector removed. It appears the problem was with the 3rd pin, heavy discoloration around the pin on the board, though it doesn't seem loose and the connector hole looks burnt pretty good. I do have a second Ultra I guess I could remove the ribbon from that one but I'm afraid it'll burn that one up as well. Any thoughts on where and how to measure the voltages? Thanks

[Enzo]

That burnt pin is most likely the problem, the female and male are not making a connection inside the connector. SOmetimes we just hard wire past it.

[Kegfish]

Thanks, I think I'm probably at my limit until I can get a schematic and find out what the pin goes to. I may just have to wait until I can send to Peavey. Thank you very much for all your help I really appreciate you time and efforts. Kegfish