Measuring Resistors In Circuit

[Paul Birkeland]

The 0V at OkC may be what's driving all the issues.  Perhaps consider posting some build photos when you get the chance.  Something like this could easily be caused by a solder bridge on the 2N2222 on that side of the PC board, or you could have no heater voltage on the EF86 on that side (the STP that feeds pins 4/5).

[Toys4Boys]

Any thoughts?

[Toys4Boys]

Huh, don't know why I didn't see your post. I'll take a look tomorrow and send some pics if the suggestions that you made don't resolve the problem.

Thanks

[Toys4Boys]

I measured pins 4 & 5, 50-56 volts both left and right sides.

[Paul Birkeland]

These are the joints I would focus on circled in red, as they don't look well soldered.  In the blue circle, be sure there's no connection between any pair of those pins.

[Toys4Boys]

I have gone thru as you suggested and get the same results. I have examined the solder connections with a magnifying headset and all looks good.

[Toys4Boys]

Is it isolated to the C4S board?

[Paul Birkeland]

The front C4S board can be installed inverted, so all the connections are reversed 180 degrees.  Doing this can be useful to see if the problematic voltages swap sides in the amp or stay with one side of the C4S board.

[Toys4Boys]

Exactly what I was thinking. Project for another day, time for some Celtics Bball.

[Toys4Boys]

Apparently the C4S board is fine, flipping the left channel to where the right was and the problem manifests on the left channel of the board now. Does that help pin it down?

[Paul Birkeland]

I would be extra sure you're getting the appropriate DC voltages at pins 4 and 5 of the 9 pin socket on the problematic side.  Those should be about 50V and 56V.

[Toys4Boys]

One question, could it be a bad tube?

[Paul Birkeland]

A bad EF86 could be swapped to the other channel, then that 0V at pins 3/8 on the EF86 socket would switch sides.

[Toys4Boys]

Pins 4 & 5 are fine, I will try swapping the tube if you think that is the next step.

[Toys4Boys]

I don't follow when you say "then that 0V at pins 3/8 on the EF86 socket"?