C4S - Wrong voltage on one side [resolved]

[Yosh]

0.26V. The working side has 2.26V on that pin.

[Yosh]

0.12 V (The working side has 2.27V.)

[Paul Birkeland]

How about pin 10?

[Yosh]

-0.35V

[Paul Birkeland]

Swap tubes from side to side, then recheck.

[Yosh]

400V on lug 20
375 on 16
0 V on pin 9 of valve socket
-0.03 on pin 10

[Paul Birkeland]

I'd be interested in seeing some photos of the build around that socket, just to see if there's anything obvious that might be wrong.

[Yosh]

I think I got it. I reflowed the solder joints on the relevant lugs. Seems like the 0.1 microF capacitor that connects through the lug 16 to pin 11 had a cold solder joint. It didn't originally but I must have created that poor connection when I removed the load resistor on that upper part of the lug - and somehow the heat was enough to effect the lower part of lug 16.

After reflowing/resoldering the capacitor on 16, I now have the correct voltage readings on both sides of the load resistor - and will take a second stab at connecting the B side of the C4S.

Phew. Thanks for stepping me through it and keeping my fingers crossed.

[Yosh]

Many thanks, Paul. That was it indeed. The heat applied to the upper part of the lug to remove the resistor deteriorated the connection with the capacitor connecting through the lower part of the lug. All is up and running - with the C4S doing its nice work.