kill_surf_city · 15271
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I would disconnect the blue wires feeding the "I" terminals on the front C4S board and redo the voltage checks on the C4S shunt regulator board above the 12AU7 socket.
Post IA, IB, OA, OB, KregA, KregB voltages. There was and still is something wrong with the power supply regulator that's built on the 12AU7 socket (which I why we have you test it early in the build), so this portion of the circuit needs to be working properly before moving along to the rest.
KregA definitely shouldn't be going that high. Are you sure that's not in mV instead of V?
Something like this could be a shorted 431 regulator, though typically we don't see them short in that manner, or possibly a jumper on the C4S board above that socket that isn't wired properly.
There's a front C4S board that sits up by the three signal tube sockets, then a C4S regulator board above the D socket. On the C4S regulator board you've shown me, I would reflow all the solder joints other than those for the LEDs. If you are using lead free solder, I would grab some 60/40 Kester rosin core solder. If you are using leaded solder, I would turn up the heat so things are a bit more willing to flow out.
