Pignose 7-100 Problem

[Khas Evets]

I know it's an amp, but it not far from a Ruby in complexity.

I have a Pignose 7-100 (the small one) that is acting funny. It works fine for a while then switches to a fuzzy, saturated sound with a slight volume drop. It also self oscillates. I can tune the oscillation with the volume knob. I've checked for any bad connections, and it appears to be related to the larger transformer or the 1000uf power filtering cap. Jiggling them gets it to stop. Also, one of the TIP41A transistors (TIP410 in the schem below) is running hot to the touch (the one on top in the picture below). I've attached a schematic from another post. Another note, my Q1/Q2 transistors are 13107's.

Besides using the enclosure for a new build, can anyone point me in the right direction to fix it? I have checked the voltages yet, but I will.

[Gus]

Cool little amps

Now first it is a amp in a box with a speaker.  So there is vibration. 

Redo all the solder connections or just the ones by the higher MASS parts, output transformer, interstage transformer and bigger caps.

Check for breaks in the traces

[Khas Evets]

Good advice. I do think the amp vibration sets it off. I'll redo those solder points. I forgot to mention, touching the larger transformer on the left side (where the windings are) stops the problem. That could either be the solder joints or a problem inside the transformer. I'll start with the joints.

[B Tremblay]

Hey, that's my amp!  I took that photo long, long ago with the idea of tracing the circuit since there was no schematic floating around.  Now there is!

[Khas Evets]

I'll take some pics too. I have it disassembled, so we'll have a front and back shot.

[Johan]

I never saw the schematic for this one before but allways suspected it was something like this...just a app.note application, perhaps slightly moded...
compare to this...

from this thread http://i31.photobucket.com/albums/c356/StebenDerMeister/muldeacy.gif

everyone knows about the "Deacy" and rumors say Micheal Schenker recorded the "Lights out" album ( U.F.O. )with a pignose...
j

[mdcairo]

Hey all, bumping this old post.

I'd like to put a pignose clone together. Anyone has some info on the transformers and diode?
I look everywhere but I only found sketchy information.
The picture above is great. Anybody has good pictures of the back side of the pcb?

Thanks! m

[dave-the-hat]

A blue diode with a  stripe is a zenner  diode. the  inter stage transformer  will most likely be as LT700 / LT44  sorry can't help on the output transformer.
if someone  could measure the resistances of the   transformer  winding it should  be possible to figure out the likely turns ratio. and you should be able to work out the  power from the circuit.
regards
dave

[Electron Tornado]

Here's another schematic: