Help with 12up4 to 12lp4 swap

[jsandlin]

I am restoring 2 Zenith port hole TV's but unfortunately both have dead 12up4's. From what I am seeing the chance of finding a good 12up4 is close to zero. I have 2 good 12lp4's I want to use. Has anyone done the swap?

They seem to physically fit the chassis is open in the front so there is no problem with clearance there. The rubber front mount fits and bolts into the chassis with no problem and the yoke is against the bell of the CRT.

The problem is that the raster is about 2 inches short all the way around the tube as if the yoke is pulled back.

The only think I can see is I am trying to use a single pole ion trap and have to have it all the way back to the socket to get a picture. I have never had any experience with ion traps I just used the one that was on the tube originally.

Any help would be appreciated.

Thanks
Jim