Finished Crack build, need help with low voltages [resolved]

[timindq]

Thanks for the reply.
Do you mean measure voltage or resistance? I want to check before applying power without the tube.

[Paul Birkeland]

Measure voltage with no 6080 installed.

-PB

[timindq]

Thanks,

Voltages are:
1 - 95 VDC
2 - 224 VDC
4 - 224 VDC
5 - 8 VDC

[Paul Birkeland]

OK, now repeat the test with both tubes pulled.

Do note that the power supply will take several minutes to drain down after you turn the amplifier off when run with no tubes.

-PB

[timindq]

With both tubes pulled

1 - 225 VDC
2 - 230 VDC
4 - 225 VDC
5 - 9 VDC

Thanks

[Paul Birkeland]

What resistance do you get between A1 and A2?

[timindq]

With or without the tube the measurement was the same. Resistance value varied like a capacitor was in circuit but averaged between 30K - 40K. Resistance shot down when I reversed the leads but would eventually begin to rise.

[timindq]

I do appreciate you sticking with me here.

[Paul Birkeland]

This sure is an odd one.  Can you measure the resistance of the 22.1K resistor across terminals 4 and 5?  You should be able to do this with it soldered into the circuit (with the amp off of course).

Either the 22.1K resistor is open, or there's some bizarre short in the circuit that I can't see that's pulling the voltage at T5 down. 

-PB

[timindq]

Good morning,

The resistance across t4 and 5 measures 22.1k. I also measured the resistance from t5 to ground with the 12AU7 in place; this measured similarly to the A1 to A2, as if a cap is in circuit. 
After work today I will recheck all wiring and see if I made a mistake somewhere that I missed the first time I checked.

Thanks again.

[Paul Birkeland]

You should be able to measure from T5 to ground without too much fuss, is it the same as T1 to ground?

[timindq]

I borrowed a better meter and performed resistance checks. T1 to ground and t5 to ground are basically the same starting at 30k and going up until I remove the leads. If I reverse the leads the circuit reads short. If I leave the reversed leads on points the the resistance will eventually climb as before leads were reversed.

Man I wish I had an analog meter.

[timindq]

Last night I did a thorough visual check of the wiring on my Crack. I see no discrepancies. Have to admit it is a easier now that I'm familiar with the thing.
After checking and measuring voltages again I decided to resolder the 22.1K resistor at t4 and t5. Voltages remained the same after touch up. T4 224VDC and T5 8VDC.
Wish there was one of those head scratching emoticons.

[Paul Birkeland]

Try putting the resistor back in.  I believe the resistor may not have been properly installed, and wasn't allowing half the 12AU7 to conduct.

-PB

[timindq]

Reinstalled the resistor and measured 22.2k ohms from B5 to A1. I used these points to ensure I wasn't moving any part of the resistor's connection. I then measured voltage at T5 and it was 9VDC. This measurement was with the 12AU7 in place and without the 6080 installed.
Voltage at T1 is 90VDC. The other side of tube seems to be working fine.

Tim