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One further consideration. The previous owner wired in a couple of input potentiometers ala Series 2. I didn't mention them as I assumed the Amp was working prior to losing some transistors. Here are some pictures, I somewhat wonder if the input/output wiring is incorrect? I would remove them...

it is not channel specific, a does it with either left or right speaker connected individually or together

no sir

OK, I brought the Variac up to 45V, and the output reading was at 7 volts. It was rising as I increased the voltage from the variac. Just to double check, I disconnected the speakers, and the out put voltage dropped to .05V with the variac all the way up to 120V. BTW, I have a volt meter inline...

I'll do that if you think it's ok to run it with the bulb lit? The variac wont do above 70 Volts due to the draw when the speakers are hooked up.

Well, still the same. hmmm

I'll give that a shot. I haven't installed the Output Relay yet. I am hoping to have the unit sorted out before making changes.

nope To simplify the issue...whenever I hookup speakers, the DBT lights up.

Still wondering if anyone has suggestions.. grounding seems fine

Thanks for the idea, I'll check that out. Long term I might WOPL this one, but the board looks nice for now. With every measurement checking out that I described, I'm willing to bet it is something simple. Too simple for me. LOL

OK, I brought them both down to .37V. No change in issue

typo. i meant .49 v i'll double check.

Ya hey gang. I have another stump the Sunnbobb issue. I'm working on an pl400 with the PL14 Board. I haven't found anything in the service manual that deals with this issue. Using a DBT and a variac, with no out puts, the amp fires up fine. With just the DBT, and fired up hard from 110V, the...

Docs sent

LOL, major brain lock. I had the bag side by side with the bag of TP9054's. It's the 9054 that I have 10 of, and need two more. Thanks for the catch. And if anyone needs 15025's, LMK.

This amp came with four 66546's as output drivers on the bottom row, and the rest of the transistors were B05's. of which 3 were bad. I have a set of 10 15025's I'd like to use, I need two more. I have removed all the B05's.. I tested the 66546's, installed them, and the DBT is behaving. Now I...

Found it. Bad RCA B05 transistor. You nailed it. Thanks for the help!

And another twist/clue. If I take out all of the row 4 transistors, and install all of the row 3 resistors, the DBT doesn't light up. Then, If I reinstall one or any of the row 4 transistors, the DBT lights up.

Took the cooling fins off, cleaned everything, there is no damage to the sockets in row 3. The weird thing is if I put any of the screws holding the transistors in row three, the DBT lights up, a single screw anywhere along the row, lights up the bulb, yet row 1 is fine.

Cool, will report back, thanks!