6080 sparking

[Paul Birkeland]

Can you reconnect the HV winding, run the amp with just the 12AU7, and report the DC voltages at terminals 1, 2, 4, and 5? 

The set of circumstances we see here isn't making a ton of sense, so it's best to double check the measurements.

[rehhy]

I re-soldered the red wire and also re-soldered a joint that looked a bit iffy around the coupling caps.

 With the test done, the voltages now look (mostly) correct:
at T1: 92.1vdc
at T2: 220.1vdc
at T4: 220.1vdc
at T5: 92.1vdc

Also, there no longer seems to be any hum from the transformer.

[Paul Birkeland]

Those are exactly what we want, now try with the 6080.

-PB

[rehhy]

Alright.

 I used the original 6080 that was supplied with the kit - it seems that once the original arc happened it knocked a bit of coating off the plates, as it also arcs a bit in the other functioning amp. The same thing happened with a 6AS7G.

 I didn't want to leave it too long as I could hear some small arcing happening inside the tube, but I let the voltages normalize as the tube came up to temp.
 
That said, the voltage measurements are as follows with the 6080 plugged in:

 T1: 175vdc
 T2: approx. 80vdc
 T4: approx. 80vdc
 T5: 175vdc

 I could use the last spare functioning 6080 I have, but if that one gets turned inside out, I'll have to order a couple more to test anything else.

[Paul Birkeland]

Those voltages look good.  Terminals 7 and 9 should show something around 100V when the 6080 is plugged in.

Do you remember which solder joint caused this problem?

[rehhy]

Yes, the voltages at T7 and T9 are 102vdc and 104vdc.

I went around the power supply and just cleaned up a couple of the solder joints, made sure nothing was dry and removed any excess solder.

The joint that was dodgy was where the coupling cap and the output to the headphone jack join at T6. I noticed that while the wires were making a decent mechanical connection, I actually didn't have solder running over the entire hole in the terminal. I did test this joint for continuity and there didn't seem to be any problem.

 Maybe it has something to do with the coupling caps? It's possible, though unlikely, that I overheated them.