CTC-5 focus problem

[frenchy]

My CTC-5 has a somewhat intermittent problem with the rear focus control. It was working, but sometimes it has a whole bunch of range (from fuzzy at both ends) but now almost no effect... now after reflowing the solder on the pot lugs, it really doesn't seem to be doing anything. Fortunately though where it is now seems to be pretty nicely focused.
Sometimes I could poke around on that board and the focus drifted so I'm thinking it might be a solder connection, but the reflow didn't help. Now after I did that, even poking doesn't do anything. Any ideas on where the connection problem might be exactly? The pot itself is relatively new (maybe a few hundred hours on it) and clean so it's not the internals of the control. Switch of the 1V2 didn't do anything. What can I rule in or out since, while the control doesn't seem to have any effect now, I do have very decent focus in the picture as it stands? Could the pot still be bad? I'm going to pull the chassis and investigate further with measurements and more solder checks and such but wondered if anybody had any helpful hints. Thanks!
Frenchy

[Don Lindsly]

The pot is very kikely bad. That is a common problem with that chassis. It is a special control capable of a couple of thousand volts scan freq AC. When the focus rectifier tube shorts, it usually takes the focus pot.

Don

[frenchy]

Turned out the cause was the pot - sort of. I had reflowed all the lugs on it (and all the resistors back there, almost all of which I'd replaced years ago for being out of range). But the center lug only appeared that the wire was well-connected to it; wire was broken but it was still 'connected' via the melted wire insulation stuck to the lug. Prepped that center wire and resoldered. Focus is working dandy again. Thanks for pointing me in the right direction.
Now I can witness the VHF stations all go dead on it tomorrow : \
Frenchy