I hate coming across repair threads with no closure or report back, so for anyone coming across this in the future:

Q15 was shorted, which looks like it was killing the bias. The "power amp in" wire in the molex connector was in the wrong spot, as suspected. Some of the outputs were blown, but I don't believe this was the original issue, I think I caused this when I removed those diodes to test.

It's up and running and sounds killer. Thanks for the help folks!

I sort of wondered if there was a meter impedance issue...the .33s were reading somewhere around 1.5, and I've already got new ones on the way so I guess I'll know soon if they read the same.

Thanks!

Thanks all - I've got a bulb limiter built and 3 new power transistors on the way (two were fried, one had an out of spec hfe). I also tested all the 5w resistors in circuit, most of which were out of spec, so new parts for that on the way as well.

Once I replace them, I'll post pics of the connectors, voltages at the test points requested, etc. Thanks again!

Some more info/clues if they're helpful:

-in trying to set the bias according to the service manual, I get .01mv across r18.  Doesn't change at all with trimpot adjustment. Bias transistor q13 checks good, as do q4 and q5 and c13.

-I read in another thread to lift a leg of each cr2 and cr8 to effectively remove a limiter part of the power amp circuit to see if that was at fault. Did that, which promptly blew the 10A fuse F3 on the power amp board.

Thanks for any insight!

Effects send and return jacks are good - they come before the pre-amp out in the circuit, which works great. I've injected signal at the power amp in with the same farty results. However, I realize this also includes the CMOS limiter. To try to isolate that, I've injected signal at C1 - same results.

However, as I mentioned in my first post, the input end of C1 doesn't seem to be connected to anything other than an empty molex pin. That's why I was hoping someone would have a picture, so I can determine if there is an error with the board connections.

Hey folks, I'm having an issue with a Sunn Coliseum 300. Here's the schematic:

http://www.prowessamplifiers.com/schematics/sunn/Coliseum_300_Bass.html

With a guitar plugged in, it gives no sound unless the strings are plucked hard - then it farts and fuzzes a bit. It sounds great through the pre-amp out jack.

I don't yet have a dummy load to use to do all of the test point voltage testing, so I'm trying to see if I can figure it out before jumping to that. I hooked up a signal to C1, assuming that's the power amp in point, and got the same result. However, I'm confused by a connection issue - in the schematic, it looks to me as though R302 in the preamp should connect to C1 in the power amp through the molex connector, but that's not actually what's happening. Instead, R302 is on pin 1 of the molex and connects to the TP6 junction. C1 doesn't appear to be connected to anything, as that spot in the molex header (pin 2) does not have a wire connected to it. Is this correct? Does anyone have a picture of the internals of this amp to compare?

Thank you!