Peavey Combo 300 won't turn off

[booj]

There's a "doohiky" that the power switch connects to, as well as the fuse holder, a resistor from one side of the power switch, and the power transformer. It's not on the schematic. Anyway its shorted, and the amp is always on regardless of the position of the power switch. (which reads good)
151[1].pdf
I figure it's a remote switcher, which allows the use of a cheaper power switch.
Anybody seen one of these? I'd ask Peavey for one but what am I asking for?

[J M Fahey]

I don't understand your schematic nor picture, but, out of the top of my head, I think they might use the mechanical power switch to turn on a Triac, which now is shorted.
Please draw the full wiring, from one plug blade to the other, including everything in that path.

[booj]

Please draw the full wiring, from one plug blade to the other, including everything in that path.

Thanks for the reply J M! the drawing is about as complete as I can make it. The round circle in the drawing is the temperature cut off sensor mounted on top of one of the output transistors. The square thing is the doohiky in the picture. Perhaps the triac device you speak of.
One lead from the power switch goes to the temp sensor. The other lead from the power switch goes to the resistor connected to the "doohiky". That tells me the dookiky responds to the signal (ac line) supplied by the power switch. The other two lugs of the doohiky connect the fuse to the transformer input. The transformer input line is also connected to the polarity switch.
It's probably a solid state relay. And it probably lost its little life when the power supply diode, two output transistors shorted, and both circuit paths connecting AC to the board vaporized.

[J M Fahey]

OK. I suggested (and still do) that you reconstruct the AC path so you can apply power straight to the power transformer itself.
Draw it (a rectangle will do) , and the wires leaving it. Some (probably 3) will go towards the diodes, another 2 should go towards AC power, going through switches, thermal sensors, doohikeys, gizmos or whatever, some of which will be bypassed to turn that amp on in the conventional way.
It's not that powerful to *need* a triac or SS Relay , but a good reason would be to avoid turn on-off thumps .
Probably you can live with them [] *and* a working amp.

[Enzo]

It is a triac. Peavey often used them in larger amps. It isn;t so much they can use a cheaper switch, it is there so the switches will be reliable. NO arcing from huge switched inrush currents. All the switch has to do is turn on the triac gate.

Look on the part, I bet it is a Q4025, or possibly a Q4040. It is a boxy thing, but it is still considered a TO3 for some reason. The base plate I suppose. Those are 400v 25A or 40A plain old triacs. Nothing fancy about them, I think Q4040 is a Trecor number, but some other brand with different numbers is fine if it meets those basic specs. PV part number is 70404040, and they would be happy to sell you one.

The identical circuit is used in the PV Renown 400 as an example, look at the mains wiring on this schematic.

Really, all you need to do is replace the triac. Probably riveted in, I drill out the two rivets, swap triacs, and pop rivet the new one in place.

[booj]

Thankyou guys. Enzo, thanks for the info! I was getting there, but it took like, 3 trys to get the gal at the Peavey end of the line to understand my email address, let alone help me figure out what the part was. Plus the Combo 300 scat didn't even show that circuit.
Mouser has those parts as
576-Q6025P5 and 576-Q6035P5