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Extended FP III Shunt Reg problem

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pdxgrampa:
This is not a new build has been in service off and on for a few years.
It would drop out briefly and then recover and then failed completely.
A side LEDs were on B side not then A side LEDS were off but MJE 350 was conducting.



H1: 24.5 VOLTS
H2: 29.4 VOLTS

A SIDE HIGH VOLTAGE                              B SIDE HIGH VOLTAGE
7:   223   VOLTS                                                  7:    222   VOLTS                                                 
9 :  213   VOLTS                                                  9 :   221   VOLTS
10; 204   VOLTS                                                 10:   221   VOLTS

 
TERMINAL
12: 116 VOLTS
15:  78  VOLTS

21: 115 VOLTS
22:  21  VOLTS

31: 78   VOLTS
32: 115 VOLTS

Paul Birkeland:
Are you able to post photos of the PC boards?

For the most part, on just about every Extended Foreplay III that I have serviced that was initially in working order, I end up building a new center PC board for the high voltage shunt regulator.

It's very easy to see if this is the issue, as the center board you have now will be a bit black under where the MJE-350s each sit.

-PB

pdxgrampa:
This the B side MJE 350

Paul Birkeland:
Can you tell me what voltages you get at:

1.  The metal tab of each MJE-350 on the center board.
2.  Kreg A and Kreg B on the center board.
3.  The metal tab of each MJE-350 on the outer boards.
4.  The metal tab of each MJE-340 on the outer boards.

-PB

pdxgrampa:

Paul here is what you asked for:

All voltages referenced to terminal 18

The voltages on the side MJE 350s and 340s are all 78 volts

Tab on A side shunt reg board 350 is 117 volts dropping slowly from 123 at first measurement.
Tab on B side is 116 down from 126

A side Kreg is 0 volts
B side Kreg  7.5 volts

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