Thanks! I checked my manual and it looks like my version and yours are not the same. In the version I have the "Nine Pin Socket Wiring" for both the 300b and 2A3 cases are the same and no LED was used...
Edit: I found a thread in the Paramount section and the two LEDs are indeed belong to a 2A3 version. Strange that I read all the 2A3 parts and couldn't find where two LEDs are used. Probably they're belong to an older 2A3 wiring.
By the way, my 300b Paramount build is 220V and I followed PJ's advice to use the 2A3 choke wiring (attached photo). All four LEDs on the C4S board and both tubes are on. Resistance check is fine. All the non * ones are correct, the * ones are slightly off but is similar to an "Doc B approved" set I found here. The voltage readings (AC voltage of 223VAC rate) are mostly good except for a few falling outside of the 10% error.
Terminal Mine A(B) Manual
1 404(407) 440
5 64(69) 71
9 175(175) 200
10 0(0) 0
16 436(439) 457
17 0(0) 0
18 0(0) 0
19 176(175) 200
A1 72(72) 74.1
A2 404(407) 440
A3 0(0) 0
A4 66(68) 69.2
6V red 2.88(2.93) 3.1 VAC
6V black 2.88(2.93) 3.1 VAC
Kreg A 3.2(3.9) 4.1
Kreg B 7.1(7.8 ) 6.3
OA 300(304) 300
OB 175(175) 200
So a few questions... before I plug in some music of course.
- The OA starting voltage fluctuated a bit around (and above) 350V a few seconds once I turn the amps on, but settled in at 300V after 10s or so. Is it acceptable?
- Should I be worry about the mismatch Kreg readings (more than 10% error)?
- I adjusted the potentiometer to read 175V at the OB pad, and I thought the reference reading (at OB, and 19?) should be 175V but it is listed as 200V. Am I missing something?
- I didn't do the hum adjustment since it's tricky to do that with the side of the 300b tube. I supposed I can listen to the speaker white noise and do that later without a meter?
