Yesterday was a great day. I needed the B-2 to be ready, so I took a half day off and spent all my time till 10:00 PM on it. It was a stressful day
The situation yesterday:
At first, I needed to come up with a solution for the LED's. Four in parallel with one resistor can cause problems. So what I did, was pretty simple, I replaced all jumpers with resistors and for the last LED (on the right) I removed the pin which makes connection to the minus trace and soldered a small wire on the minus leg of the LED inside the original rubber lamp holder. Afterwards I connected a resistor on it and soldered it on the minus trace of lamp number 3. In that way all LED's have their own resistor and the board was kept original.
I used 820 Ohm resistors to get 12 mA on the LED's and I used 140 degree radial beam warm white ones.
Then the speaker switches, they needed to be cleaned and conserved. They had to be desoldered from the board in order to do it.
I was pretty shocked by how clean they already were
Just some mild oxidation.
Internal parts were deoxidized and faderlubed, the mechanical parts were lubed. The board was cleaned afterwards.
Forgot to take after pictures.
Then I replaced the orange +85 and the -85 green power supply wires between the power board and the driver boards. The old ones were pretty brittle and have broken off a few times during the process. I used some nice silver plated wires in original color, but with larger diameter. I also changed the E wires between driver boards to power board with black ones to suit the internal design.
Then it was time to reinstall all boards.
Then it was time for first start-up. Exciting!
Bias pots closed, meter hooked on +85. Power on, CLANG! Nice.
+85 and -85 were still spot on.
Then bias and dc balance. I'm not very happy about the Bourns single turns. Very hard to adjust bias at a round number. Took me half an hour to get them both at 60 mV. But it remains stable. Dc offset is around 1 mV.
Not too happy about the LED color, they are too yellow. Maybe I need to change them.
Some listening tests, sounds great!