Speedball 1 & 7 channel high voltage

[BrettMatthews]

Hey guys, I just finished installing my speedball into my crack which was working great before. I am just having one small problem now, my voltages at terminals 1 and 7 are out of spec, all other voltages are fine. Voltages are as follows:

1 - 116
5 - 101
7 - 127
9 - 117

So my B side is is right around the range of the upper specs, but my A side is definitely out.

All LEDs light up (the ones on the small board arent as bright as the rest though, not sure if that is normal or not), I have triple checked resistors and they are all correct, and I have gone over most of the solder joints.

Any suggestions are greatly appreciated.
Thanks
Matthew

[Paul Birkeland]

Does the voltage at T1 change if you run the Crack without a 6080?

[BrettMatthews]

Yes the voltage does change if I remove the 6080:

1 - 91
5 - 78

[Paul Birkeland]

It shouldn't, is the B+ wire from the big board going to terminal 1 or terminal 2?

[BrettMatthews]

The B+ wire from the big board is going to terminal 2.

[Paul Birkeland]

The connection at B4 is very close to touching B3, if they were touching with a 6080 in the socket, that could have some unpredictable results.

[BrettMatthews]

It must have just been the camera angle as it definitely wasn't touching, but for good measure I trimmed it and retested but there was no change.

[Paul Birkeland]

I'd go over your solder joints then, both on and off the boards.  The functioning of the small PC boards is independent of the large PC board, so if running both tubes causes odd performance in the 12AU7, then there may be a marginal joint.

[BrettMatthews]

So I've had a chance to work on this some more but still haven't been able to solve my issue.

I have tried swapping the small boards and the problem did not follow the small board so it's not an issue with those, and I have rechecked the solder on 1l and 1u and the tubes that those spots are going to and that didn't help either. The voltages did come down a little bit after I reflowed the joints on the large PCB (good side is about 90 and bad side about 108) but the one side is still out of tolerance. Any other thoughts or spots I should look to?

Edit: reflowed the solder on the big board again, no change.

[Paul Birkeland]

Such a problem could also be caused by weak heater voltage.  This is the red/black twisted pair of wires that feeds from power transformer terminals 4 and 5 to B7/B8, then down to A4/A5/A9.  Removing the 6080 removes most of the load on this feed, and could allow for the 12AU7 to properly heat if there's a marginal connection here. 

It's possible to measure this voltage, but I would recommend reheating ALL of the joints mentioned above. 

[BrettMatthews]

Thanks again for the suggestion, sadly it still did not fix the issue. I reheated all of the suggested points but did not bring the voltage down at all.

Is there a chance this could be tube related?

Edit: Since you said it is possible to have these voltages I decided to give it a try and see how it sounds (work setup, e10, dt770 250). A couple things I noticed were the noise floor is quite high overall, and if I tap on the metal top plate I can hear it from the right driver, I hear a ting sound, but only really from the right driver. Not sure if this points to anything or not though.

[Paul Birkeland]

Set your meter to AC voltage, ground one probe (sometimes easiest to smoosh it under the solder tab at the #8 screw back by the IEC), then carefully measure the AC voltage at A4, then measure the AC voltage at A9. 

This is very unlikely to be tube related since the 12AU7 works fine without the 6080 installed in the amplifier.

[BrettMatthews]

Okay so the ac voltage measurements are as follows:

A4: 0.01vac
A9: 5.8vac

[Paul Birkeland]

There's a very slight chance that a different 12AU7 might give different results, but there isn't anything about the installation of the Speedball that would bring about these changes unless something fundamental to the circuit was disturbed or altered. 

If at all possible, with the little board pulled up and out of the way, can you confirm your voltage at A8?

[BrettMatthews]

Voltage at A8 is 0Vac.