Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Eros Tape => Topic started by: keithp on July 04, 2015, 11:37:58 AM
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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?
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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
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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
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Here is what I measured:
IA 292
OA 223
IB 291
OB 87
KREG A 5
KREG B 0
Thanks for your help
Keith
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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
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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.