RCA 621ts Restoration

[old_coot88]

I need to learn to re-read stuff. Doh.

[vts1134]

Making some more progress on the set. I went though every resistor in the horizontal circuit and replaced quite a few that were way out of spec, or completely open. I fired the set up after each replacement to make sure nothing went wrong, and to enjoy seeing the picture get better and better with each step. I still have (at least) two problems with the video currently. One problem I could not get completely sorted out with resistor replacement in the horizontal circuit was a bit of tearing at the top of the screen.

It was easiest to photograph the phenomenon by injecting video right at the grid of the video amp and adjusting contrast until it showed up. It is possible to get a stable picture most of the time, but when there is full motion video on screen it will occasionally tear horizontally at the top of the screen, just like the picture above but some times much worse. The last set I worked on had a Sams for it and gave a procedure for horizontal adjustment. I cannot seem to find one in the Rider for this set however. Maybe it's just a matter of adjustment that I'm missing?
My other problem is before the video amp. I'm getting some trailing ghosting in the picture.

I haven't dived into this problem just as I would like to get the horizontal sorted first but thought I'd share.

[old_coot88]

In regards to those trailing ghosties, be sure and check peaking coils L105 and L106 for continuity.

Seems like the tearing/'flagging' is related more to signal overload than horiz. adjustment since it straightens up as you lower the contrast. This set doesn't appear to have any AGC (automatic gain control) at all. The contrast ('Picture') control adjusts the gain of the 2nd IF tube, requiring you to manually adjust it for varying signal strengths. Too strong a signal and the pic gets the bends. Just one of the charms of the old beasties, sorta like riding the gain on an old TRF radio.

[vts1134]

Originally Posted by old_coot88

In regards to those trailing ghosties, be sure and check peaking coils L105 and L106 for continuity.

Seems like the tearing/'flagging' is related more to signal overload than horiz. adjustment since it straightens up as you lower the contrast. This set doesn't appear to have any AGC (automatic gain control) at all. The contrast ('Picture') control adjusts the gain of the 2nd IF tube, requiring you to manually adjust it for varying signal strengths. Too strong a signal and the pic gets the bends. Just one of the charms of the old beasties, sorta like riding the gain on an old TRF radio.

L105 and L106 read a bit low on my voltohmist but they are in the neighborhood.
I've shot a couple of videos of what the set is doing. The first one is from the B&K 1077 and shows that the two problems seem to be interrelated. When I adjust the picture control I can get a steady picture with ghosting, or a ghost free picture with tearing, but not both. The ghosting is much easier to see in the black blocks at the bottom of the screen (is there a proper name for those blocks?).
http://www.youtube.com/watch?v=rLJRdzFB-yU
The other video displays the occasional horizontal tearing towards the top of the screen with full video that I described before.
http://www.youtube.com/watch?v=28X9hkIWCQE
I'll check the resistors and voltages in the video and if stages next to see if anything jumps out there.