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Author Topic: shunt regulator voltage is low [resolved]  (Read 1968 times)

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Offline keithp

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shunt regulator voltage is low [resolved]
« on: July 04, 2015, 11:37:58 AM »
I am testing the shunt regulator voltage before proceeding with the signal path wiring. One channel is perfect at 225 volts and the other one is only 95 volts. I switched 12BH7 tubes and get the same results. I am proceeding to dismantle the board and rewire. Any suggestions?
« Last Edit: July 11, 2015, 04:20:13 PM by Caucasian Blackplate »

Online Paul Birkeland

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Re: shunt regulator voltage is low
« Reply #1 on: July 05, 2015, 07:39:29 AM »
One channel is perfect at 225 volts and the other one is only 95 volts.

You have a short at your socket, between D2 and D3 or D7 and D8.  This is grounding either D3 or D8 through one of the 220 Ohm resistors, which gives you ~100V instead of 225V.

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Online Paul Birkeland

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Re: shunt regulator voltage is low
« Reply #2 on: July 10, 2015, 10:15:21 AM »
Hello Keith,

Just checking in to see if you've made any progress.

If this suggestion did not solve the problem, can you post these voltages:

IA
IB
OB
OA
Kreg A side
Kreg B side


-PB
« Last Edit: July 10, 2015, 10:22:34 AM by Caucasian Blackplate »
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline keithp

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Re: shunt regulator voltage is low
« Reply #3 on: July 11, 2015, 08:50:12 AM »
Here is what I measured:

IA        292
OA      223

IB      291
OB     87

KREG A      5
KREG B      0



Thanks for your help
Keith

Online Paul Birkeland

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Re: shunt regulator voltage is low
« Reply #4 on: July 11, 2015, 11:29:22 AM »
KREG B      0

This is very indicative of a short between either pins 2 and 3 on the 12BH7 socket or pins 7 and 8.  (Sorry to sound like a broken record, but the voltages are strongly pointing to this)

It's also possible that the Kreg on the offending channel isn't connected to the correct pin on the 9 pin socket (should be 3 or 8).

It's also possible that the wire intended to go to Kreg is going to -reg.

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline keithp

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Re: shunt regulator voltage is low - fixed
« Reply #5 on: July 11, 2015, 03:35:51 PM »
I found a bad solder joint in the ground circuit on the shunt regulator board. Resoldering the joint seems to have fixed the problem as I am now getting ~220 volts on both of the red leads.