Stabilizing a TS-18

[Zenith26kc20]

This weekend revealed a problem I have never seen before. The vertical centering control had gone down to 1 megohm. This disabled both horizontal and vertical centering! I pulled the leads loose connecting the two controls and ohmed them out, the vertical being low. I went so far as to pull the control to be sure it was down in value. It is still linear thru it's range and the tap is correct in being half (.5 meg) on each side of the control. I put some 1 meg fixed resistors in place of the control and the horizontal centering works great. I may try adding one 470k resistor in each leg of the control to bring it back to 2 megohms. If the centering is adjustable enough (right now, with the fixed resistors it's nealy perfect) I may just leave it like that.
Now the snowy picture has to be tackled!
Oh, that is my test 7 inch CRT. I am very careful with the 8 inch. That one came from the bakelite TS-18 that is really nasty. Someone put some green plastic to hold the CRT in place and it melted everywhere. It took me an hour to scrape the bell and face clean. It's a Philco tube and it is in great shape!