GE 800D restoration

[bandersen]

Slowly making progress. Very frustrating set to work on!

Went over the horizontal circuit testing every mica cap and subbing when in doubt. Nothing made any difference.

Vertical hold was improved by replacing the marginal 12AU7 video amp and cleaning the vertical hold control.

Another issue has been the contrast control. I only got an image for about the final 20% of the control.

This control straddles the two B1- and B2- buses and provides grid bias for the tuner RF amp and 1st IF stage. I don't believe this set has AGC.

There is a string of three resistors between those two buses that establish the voltage difference between them. One of them - a 47 ohm - was measuring about 90. Replacing that gave me about 35% action on the contrast control.

It's still finicky, but with patience I can get a stable, watchable image.

That leaves the vertical fold on the left side. I saw a slight bump in the sawtooth wave on the HOT grid, but I think it's more likely some ringing in the yoke or damper somewhere.

This is with a 5AXP4 test CRT so I'm not concerned about the focus or off center image.