Anyway I first turned the amp on this past Sunday. The only significant problem was some really loud hum. I used a single point ground bus approach with some #12 solid wire. It runs across the front of the amp. Everything was grounded to this seemingly good ground conductor. After much AG reading, I decided to make some changes. Now, the amp is very quiet. Here is what I did . . .
1. Moved the presence 390 and 1 uF off the bus and onto the back of the bias pot (ground C . . . on my sketch).
2. Moved the incoming ground, transformer ground, and heater resistors to a separate ground near the transformer (ground B).
3. Put in a new ground screw and lug near the front bus and connected the bus to his separate ground (ground A) directly. This made a huge difference. The connection through the front panel must have been pretty bad.
4. Moved the B+4 and B+5 ground to the front ground bus (ground A).
5. Moved the B+2 and B+3 ground to the chassis near the bias pot (ground C).
6. Moved the 100uF/220K filter section ground to the to the transformer ground (ground B).
7. Moved the bias cap ground to the transformer ground (ground B)
The amp sounds great. I can't belive the sounds coming out of this baby. Still have a lot of tweaking to do as I substituted a lot of parts to get it going (2 old power tubes, 8 year old filter caps, parallelled small caps, etc.).
Thanks again. Hope this stimulates some ideas for someone in a similar situation.
Boog
