I've been reading the thread, trying to soak it up. I'm going to just say that I got from this, so correct me if I've missed something.
> PT and OT resistance measurement seem normal. I think that "UL" reading may just be what your meter says on a complete open circuit.
> PT and OT don't seem to have external shorts. Overcurrent seems to be related to just the output tubes being in.
That seems to me to indicate that something is wrong with the output tube circuits (um.... duuuh...
) and you have reasonably eliminated a bad tube. New electrolytics and checking components/shorts seems to eliminate a failing electro.
Observations and questions:
One of your posts said: "Primaries I get .84k ohms to each plate. And 2.5, 3.5 and 6.5 to ground for 3 primary wires." about the OT. Is that right??? If any of the OT primary wires are under 10 ohms to ground, you're going to get overcurrents through it. Can you re-check that and try to verify that? Was that taken with the tubes in or out? Ideally, put the tubes out and with the line cord unplugged, measure from output tube socket pins to ground for the two "outside" connections.
On the output stage itself:
This circuit relies on the current through the shared cathode resistor for reverse bias on the output tube grids. A failure of the bypass cap on the cathode resistor R241 would likely cause what you're seeing. So would getting the polarity of the bypass cap C224. So would a short to chassis of the cathode leads of the output tubes; however, your test for shorts should have eliminated that.
> Is the cathode bypass cap C224 absolutely, positively soldered in correctly, not backwards?
> With the AC line cord unplugged from the wall, what is the DC resistance to ground from the plate, grid and cathode pins in the sockets for the output tubes?
> With the output tubes out, IIRC you can power it on and it does not overcurrent. With only the output tubes left out, and it powered on, what are the DC voltages on the filter caps?