Advice on dealing with a focus element issue in a 21AXP22

[Electronic M]

So I've been working on a CTC-4 I got from a member here. The set came to me making a raster on original caps.

It had some arcing noises. I eventually discovered they were from the CRT when unplugging the CRT hv lead caused the noise and unstable 1.2KV DC read on the main B+ line to go away and stabilize to the rated 350V DC respectively.

I tried to discharge the HV then pulled the shroud and got a good bite off the CRT anode cone...I then realized the HV connection spring was missing 1/3 off its end, and mashed against the insulator (thus to reach the CRT it had to arc)...Folding it out to make contact caused it to snap off so I robbed the same part off of a spare CTC-4 CRT insulator shroud I have...That fixed the arcing and I could get the set to pass lousy color video with lots of issues with HV stability etc.

With low HV I could get a full screen focused picture that would intermittently be part way swamped or completely out of focus by hum (seemed to be synched to vertical most of the time, but occasionally would roll or be gone for 30sec).

Once I recapped enough to get stable HV I began to realize I can't get focus with the HV normal. The focus seems to be stuck WELL under 1KV, and was loading the focus rect tube down to 2KV through the series resistors.

Now at the end of the night I confirmed that disconnecting the CRT socket restores focus voltage to normal 3-4KV...

The CRT does not show signs of gas (if it did I'd expect the HV to arc to the focus and some neck glow).

I'm probably going to continuity check the focus tomorrow. I'm pretty sure my tester doesn't have a 'remove focus shorts' setting. How should I clear the focus element short I expect to find tomorrow?

[Electronic M]

Today I learned that on a CTC4 if the screens are set too high it can load the focus down ...got a good focused crosshatch displaying right now.

[old_coot88]

[Electronic M]

This is as far as I got.
IMG_20190421_205249100 by Tom Carlson, on Flickr

The can lytic cluster is still original as are all the papers in the audio section, the low voltage lytics in the HV cage, and there may be a paper composition domino hiding somewhere.

Color lever varies horizontally across the screen, color lock ain't terribly stable from power up to power up, and dynamic convergence won't exist till I install the chassis...I've got it connected to the cabinet on cable extenders, but didn't have one for convergence so I left the one in the set unplugged and grabbed a second one (from my Seville) to use as a dummy load for the chassis.

[Rocket]

Very nice! Cant wait to see how this looks as you work on it : D