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RE: questions about Scott 222B phase inverter

Posted by microbe (A) on August 27, 2016 at 20:30:29

In Reply to: RE: questions about Scott 222B phase inverter posted by FenderLover on August 27, 2016 at 19:28:53:

Hi,
Yes I did change all the caps in the power supply. Here are the readings I got for the different nodes (in parentheses) along with the values shown on the schematic:

node 1 (right after the 5AR4)- 375 VDC (378)
node 2- 365 VDC (372)
node 3- (to center tap of output transformers)- 350 VDC (361)
node 4- (pin 9 of 6bq5)- 310 VDC (343)
node 5- (to the plate resistors of the 6BL8)- 280 VDC (312)
node 6a- (to pin 3 of 6BL8)- 105 VDC (93)
node 6b- (to the plate resistors of tone circuit 12AX7's)- 270 VDC (271)
node 7- (to the plate resistors of the phono amp 12AX7's)- 205 VDC (219)

So the voltages don't seem to be too far off, maybe a bit high. I actually plugged the amp in and played some music through it, doesn't sound too bad. I'm really surprised this thing will work with these low voltages on the 6BL8 plates. I guess I'll leave everything as is for now since it seems to be working. Thanks.

Bill

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