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Dang it. false reading. Replacing the resistor did not fix the issue. Square one squared

I didn't say Saint! hahaha

You're my hero Gene!

Got it! I found the R39 10 Ohm resistor was reading 15 ohms in circuit. Replaced it and now have 11.9 ohms in circuit, the other 3 are reading 11.5ohms in circuit, so close enough. and the problem went away! I just noticed I've been upgraded to journeyman, is that because I read all 228 pages of...

both check out...

Replaced D14, D15, and the Q7's. Arg. Nothing changed. Yes, that's an Oxford comma.

next up I'm going to pull and test q7

Progress I think. I removed each transistor one by one. The DBT went out on only one. The bottom transistor in row one [Lower right by transformer]. I replaced the transistor with another, and the DBT still lit up, and went out when I removed the transistor. The DBT did not go out when I removed...

Narrowed in on the issue. Removed both rail fuses and the dbt does not light with speakers attached. Replaced right fuse (as viewed from back of amp), and dbt does not light up with speakers attached. Removed left fuse, and BDT lights up with speakers attached. With left fuse still installed...

done. thanks!

I lifted the legs on d9 and d10. No change

Working on a PL400 (different than the one with the DBt issue) and would like to replace the Q1 and Q2 TIS97 transistors as recommended by the manual to correct high DC offset. Mouser and Digikey both list the TIS97 as obsolete. Although Mouser lists a substitute, the specs for the sub don't...

Good thought, that would explain the problem being on both channels. I'll give it a shot, Thanks for the idea!

Has me befuddled too.

I tried that when I removed the pots... I also checked the jacks, and they test fine as for grounding and connectivity.. sigh, I've hunted the schematic, and don't find any clue. Another cup of coffee, another pondering session.

Thanks George!

Done. No change... I even swapped out the bottom row with tested and matched 410's. I'm at a loss.

I taught myself everything I know... and I still don't know anything! I brought it up that way, but I did not have the speakers hooked up, so I had no indication of trouble. I'll try it in reverse as you suggested, this time with speaker testing. Thx Gene.

Well, that wasn't the problem. dbt still lights up with speaker hooked up.

nice!