Thank you for your answer
Here are my voltages:
terminal:
1 - 83VDC
2 - 166VDC
3 - 0VDC
4 - 166 VDC
5 - 86 VDC
6 - 0VDC
7 - 105 VDC
8 - 0 VDC
9 - 107 VDC
10 - 0VDC
I redid all the solder joints again now, not luck. I'm very certain that I don't have a bad solder joint. I'm an electronic engineer myself, I solder quite a lot at work.
I used sand paper on the tube pins also for better contact.
Could this be in the sockets? Should I use some contact spray?
What if it's really a tube, how could I prove this?
I don't think it's in the power supply part, that would affect both channels right?
Could this be resolved when I install the Speedball?