trinityamps.com

The divide and conquer strategy is a good one. But I don't see how disconnecting C7 from the power rail isolates the power amp. Removing R10 would shut off power to the preamp, leaving only the power section running.

But if the amp doesn't blow fuses with C7 disconnected, it sounds like C7 is the culprit. Check it for shorts.

Thanks Mitch...actually what I did is disconnect the wire running from C7 to the junction of R16 and R17 on the terminal strip by the power tube.

But I think I've finally found the culprit...after hooking everything up again per the layout diagram, I powered it up and the current limiter bulb came on...shut it down and thankfully didn't blow the fuse. I started working backwards from the preamp this time, first disconnecting the C6/C7 as described above. Still shorted. Then sequentially disconnected all the wires from the preamp socket just in case the heater wiring was shorting out on a little wire strand or something....still shorted.

maybe one of my wires came loose under the board?....So I removed the nuts holding the board to the chassis and lifted the board up to the top of the screws, just enough to keep it in place. Powered it up...no short. I go and get my telescopic inspection mirror and look under the board. No dangling wires or anything, but It appears that one of the output transformer bolts is directly under the leg of either R19 or R26, the 2 power rail resistors mounted underneath the board. That's gotta be it.

Should've thought about insulating those legs...just didn't occur to me at the time.

The weird thing is that when I powered it up the first time after I isolated the power amp and there were no problems, when I took the board off I noticed a tiny little chip on one of the resistors. Guess that was from the transformer bolt hitting the resistor body. When it went back in a second time, maybe I installed it at a different angle...the resistor must of have slid over and the bolt made direct contact with the leg.

So this board is coming out one more time...going to go ahead and put the VRM back in, insulate the legs of R19, R26, and get this lil Tramp some tubes!

Would there be any problem moving R19 and R26 above the board? I could splice some 18g solid core wire on them to extend the legs.

Good news. Sounds like you found the problem.

You can mount those resistors above the board. It would be a good idea, the less stuff under the board the better.

Just connect them in parallel across each of the two capacitors. You might not even have to extend the leads. Leave a bit of space between the resistors and capacitors, though, in case the resistors get hot.

I ended up going with the original layout and went below the board. Got everything wired up and powered it up...everything looked good. Installed the tubes and connected the speaker. All voltage readings were spot on with the schematic except that both plates on the 12AX7 were about 10VDC lower than spec.

The amp is ridiculously quiet! No hiss or hum...At first I thought I didn't attach a speaker. In any case it all came together really good...4 years in the making and I finally got around to finishing it. Other than the bone-headed mistake with the short on the transformer bolt, this went together like a charm!