Help troubleshooting SE Pentode amp

[Carlp]

I've built Eli Duttman's Dirt Cheap Single Ended amp from here:
Audiophiletalk - DIRT CHEAP SE amp
This is a 6BM8 amp, and I'm using a Russian counterpart. Having problems with one channel and someone on that forum is trying to help, but the other forum just doesn't have a lot of people willing to give me ideas. Schematic attached.

One channel works well, the other produces nothing. I've checked, rechecked and checked the wiring again. Even unsoldered and tested some components. Resoldered many joints though all looked good.

Troubleshooting so far: swapped tubes, swapped inputs, swapped speaker leads, wired in a new pot. I even moved the OPT primaries from each channel to the other, while disconnecting the feedback. In this case the problem switched sides, so it seems like there's a wiring problem and NOT an OPT problem.

B+ is 227V, drops to 150V at the triode plate on the problem side (L) and 118V on the right. Triode plate load resistor drops 100V on the good side, 70V on the bad (there are a few other items dropping voltage before the load resistor). Pentode voltages all seem fine (and pretty much the same) for each channel. Both channel heaters read close to 7V, but the problem side seems to glow noticeably less, even with each of my 4 tubes. I'm running a 12.6VCT transformer with AC on the heaters in series. Finally, problem side cathode (for the cathode) reads 2.3V whereas the good side reads 1.6. Pentode cathodes read 16V and 15V L and R. Oh, and DC voltage drop through the OPT primaries is 5V L side (problem side) and 4.75V good side.

Anyone have any ideas? On a suggestion from someone on the other forum, I am going to try to measure current in the cathode, but I don't have a way to do that yet.

Thanks, all.

[DF96]

What is the voltage at the junction of R10 and R11? Have you checked the values of these two resistors? Is there any possibility of a positive voltage being applied to the OPT secondary, as this would affect the triode bias via R13.

It looks like the triode is being biased back, although I would expect low output rather than no output.

[Carlp]

Well, DF96, you may have hit on something. I get about 1.1V at the junction on the left (problem) channel, and about .05V on the other side. So...that could be the voltage problem. That, of course, made me look more closely at the R11 resistors, and in fact, they appear to be different. The R side IS 100R, but the left/problem side looks to be in the K ohm range. I'll double check, fix as needed, and get back. Maybe later tonight.

Thanks a ton for that pointer!
Carl

PS - I had one other amp for which I made a similar mistake and it took me a long time to find. Odd how that works. I can look it over and measure, and just not see the problem.

[Carlp]

Ahhhhhh. I'm listening to the new amp late tonight and it sounds quite nice indeed.

As it happens, R11 on the left side was 100 K ohms instead of 100 ohms. Replaced it and got sound immediately. This is (sadly!) similar to the mistake I made on Eli's El Cheapo to which I referred earlier. Strangely, that error was also in the cathode resistor. But I'm very happy to have resolved this issue.

Thank you so much DF96. Your work is done here. Wish I could pour you a single malt. Guess I'll have to pour one for myself instead...

Carl