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Yeah, thanks guys. I'm going to follow the power by tracing the schematic from the jumpers, all the way till I find something. I'm at a loss to explain why it's been so difficult to find where the power stops. I've already checked every connection with a DMM while also doing the wooden stick...

Comparing the two boards, all is well and equal for the B+ and B- voltage. Left board, the good one, shows correct voltages at base and emitter of all TO-3s, roughly .380V. Right side bases and emitters are dead. Collectors on both sides show appropriate voltages. As stated earlier, there are no...

Thank you. Most appreciated. I'll get at it today and let you know what I find.

No, there isn't a problem with the screws. It's just that I use hundreds and hundreds of the things in some sprint car fabrications I do, and the ones I used on the TO=3s were from different batches. They vary in absolute length (which isn't critical for the units I produce) depending on what...

No. Sorry. My mistake, again. After the DBT test, I unhooked it from the amp and then plugged the amp directly into an outlet. At that point, I tried to play music through the two channels. The left sounded great. After the right channel produced such terrible sound, I unhooked the speaker and...

"I ask one last time, did it come up on the DBT WITH BIAS the first time or was bias dead on the one channel (one channel was dead)?????? Did you ever get music from both channels at the same time? (clear, undistorted, full volume music through one channel only, left channel)" — In order to be...

Okay, the first issue is that those are old photographs. The bias transistors have been replaced and the holders aligned properly. I did a reflow on all the wires from the backplanes to control board. They are solid and I've checked them with a magnifying glass and DMM. I followed Joe's...

Yeah, sorry guys. Thanks for all the help you've given to this and other projects. It must be frustrating that I don't work straight through and finish this thing. Unfortunately, that hasn't been possible for me. Truth is, I'm fully disabled, and when, what, and for how long I can work on things...

Resurrected amp project. Half way there. Powers up fine. Relay clicks. Left channel has good bias and puts out great sound when connected to source. Right channel almost dead. A very faint crackling sound, like a bad connection, but no volume to speak of. No/zero voltage at bias check point. All...

Well, I don't know if I solved the mystery, but I found something. First, I took the pot back out and completely disassembled the unit. As one of you predicted, it was clean and fine. However, the two 1000uf 50v caps that sit behind the pot were loose. I noticed this the first time I went in...

The way this all started was when I hooked the unit back up and turned it on, for the first time in a about a year, I was getting hum. When I fiddled with the knob, it varied, but didn't go away. I pulled the cover and fiddled with the body of the pot and was able to generate even more...

All by itself, on the bench, 120VAC measured, voltages appear to be spot-on: +15.15. -15.03/ +18.45, -18.55. What next? There was speculation that the pot was not the issue. However, the hum was there at zero volume, but gone by 1/3 volume. Why would it disappear, other than because of the pot...

Thanks for the input. I'm going to check those readings tomorrow. But are you aware that there has been a modification to the power supply? It's in this thread. The modification was vetted by everyone who looked at it. One of our community even printed up the new boards. I don't think that...

I did not take it apart because of the starlock on the back of the shaft. All I did was get some space between the two mods, then used DeOxit, several times, along with air to gently blow it out. After that, I used the DMM to check the ohms, and something wasn't right at the zero mark of the...

Thanks, but yeah, I checked all the voltages. Also, the damn thing worked just fine for a long time. This is new. It's improved since I cleaned the pot, but it didn't go away. And when I put the pot back together, still off the board, I checked it with a meter, and it was doing weird stuff. The...

My 3300 sounds fantastic! Unfortunately, there's hum that seems to be coming from the volume pot. I pulled the pot, took it apart and cleaned it thoroughly, then carefully resoldered. The problem went away initially, but came back after the unit was up to temp. The hum is loudest at 0 volume...

I'm just going to replace all the important parts. It doesn't cost that much to do so, and then I'll feel more confident when I bring it up again.

Both Q7L and Q8L appear to be blown. At least that's what my DMM is showing with them in circuit. Since I have to pull the board anyway, I'll remove 7 and 8, and test them out of the circuit, just for curiosity. Of course, I'm going to replace them as well. I have a few 651s. I'll have to order...

Isn't that covered by the Dark Lady Sonnets, #127–154, regarding failed connections?

Thanks Joe, I'll definitely do more testing tomorrow.