Measuring Resistors In Circuit

[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"?

 

[Paul Birkeland]

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

That's where OKC connects.

 

[Toys4Boys]

Woo Hoo!!! Listening as I type, first impression is good but need to break it in and do more listening.

Thanks for your help Paul, in the end I'm not sure what did the trick, though I did manage to snip my 3L A2 A7 lead at some point.