Finally making some real progress on this set after 18 months!
The sweep board is done including rebuilding the vertical integrator couplate using C0G type ceramic caps.
After reinstalling, vertical hold was rock solid, but CRT anode and boost voltages still about 40% low.
I thought maybe an impedance mismatch using the CRT substitution box was the cause.
So I hooked up the set's yoke with an 8XP4 propped in place. It made no difference what so ever.
I did some more research and discovered the voltages and waveforms in the Riders service info for the horizontal circuit differed from the Sams and matched what I was measuring.
I also noticed the Riders shows a 6CU6 HOT while the Sams a 6DQ6. Sure enough that's what's on the tube chart.
So I dug up a couple 6CU6s and tried them. HV was even lower !
The specs are very similar though so I went back to trying some NOS 6DQ6s.
Bam, finally as I was about to give up, I found a 6DQ6 that got the voltages right where they should be!
I've never encountered a set so picky about tube before.
Now with 15+ kV and a 520 V boost, the image more than fills the little test CRT screen and the focus is sharp.
I do get some interference on the screen, but otherwise the set is working very well. Next I'll make sure all connections are tight and all shields are in place.
