[Resolved] Crack OTL - Voltage Check Issues

[awkatche]

Just finished assembly of the Crack OTL. Passed resistance checks - terminal 6 had an issue originally and was registering infinite resistance, but re-soldered the right channel connection on the headphone jack and that resolved it.

For voltage checks, I verified that the tubes glowed. At first, I registered a voltage of around 90V on terminal 1, but then it dropped to 0V. Now all terminals 1-5 are at 0V. Terminals 7 & 9 read around 70V, while 6-8-10 are at 0V. The LEDs on the 12AU7 didn't light up (or if they did it was too faint to notice).

Thoughts?

 

[awkatche]

Photo in case that helps

 

[Paul Birkeland]

Often issues like this will be resolved if you reheat all of the solder joints in your amp.  By that I mean heat the joint for at least 10 seconds for all joints except A3 and A8, which take the least heat to solder and are probably OK.

I would suspect that the red wire leaving B2 and heading up to the front of the amp isn't well captured by solder.

 

[awkatche]

Thanks. Following your advice I checked resistances down the power line from terminal 13. As you guessed, the connection at B2 wasn't strong. Re-soldered and now all voltages check out. Thanks!