questions about Scott 222B phase inverter

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Posted by microbe (A) on August 27, 2016 at 18:49:27

Hi,
I'm finally getting around to refurbishing a Scott 222B that's been sitting on my shelf for the past year or so. I replaced all of the electrolytic and film caps and brought it up on a variac today to check out the voltages and make sure everything looked as it should. Well, overall not too bad but the 6BL8 phase inverter does not look right to me; the voltages are really off. One thing I noticed right away is that the plate resistors for the triode and the pentode are 220k ohms instead of the 100k ohms shown on the schematic. The voltages on the plates are not even close to what is given on the schematic: 40 VDC on the triode (should be 78 VDC) and a measly 7 VDC on the pentode (should be 60 VDC). The cathode voltages are both close to spec. Could this amp possibly work under these conditions? I guess I could try playing some music through it and see what happens. Should I change those 220k ohm plate resistors to 100k ohm as specified on the schematic? Any advice on how to proceed would be much appreciated. Thanks!

Bill

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Topic - questions about Scott 222B phase inverter - microbe 18:49:27 08/27/16 (14)

I deleted two posts but now I think I may have the answer - Michael Samra 21:29:02 08/28/16 (2)

RE: I deleted two posts but now I think I may have the answer - microbe 11:15:07 08/29/16 (1)

RE: I deleted two posts but now I think I may have the answer - Michael Samra 00:44:01 09/04/16 (0)

RE: questions about Scott 222B phase inverter - fredtr 10:27:04 08/28/16 (2)

RE: questions about Scott 222B phase inverter - microbe 13:16:19 08/28/16 (1)

RE: questions about Scott 222B phase inverter - fredtr 17:23:41 08/28/16 (0)

RE: questions about Scott 222B phase inverter - Eli Duttman 21:50:05 08/27/16 (0)

RE: questions about Scott 222B phase inverter - FenderLover 19:28:53 08/27/16 (6)

RE: questions about Scott 222B phase inverter - microbe 20:30:29 08/27/16 (5)

RE: questions about Scott 222B phase inverter - FlaCharlie 12:18:50 08/28/16 (4)

RE: questions about Scott 222B phase inverter - microbe 13:30:08 08/28/16 (3)

RE: questions about Scott 222B phase inverter - FlaCharlie 19:06:38 08/28/16 (2)

RE: questions about Scott 222B phase inverter - microbe 11:08:08 08/29/16 (1)

Keep Us Posted - FlaCharlie 10:53:32 08/30/16 (0)

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