I wonder if this could be horizontal garbage on the contrast control line? Can you see any pulses on the contrast control? Are all caps connected to it good (C7, C6, any others that may be off the edge of the schematic you posted)?

Edit: you could try bridging these points to ground with a spare 50 microfarad.

I have now directly connected video from my generator to C28 which connects to pin 1 of V9 of the 6AU6 video amp. The picture is now clean. The white line is gone. The problem must be in the IF system ahead of the 6AL5. How would you track this problem in the IF stages to locate the problem?

Try AC shorting the grids to ground, through a cap,
going backwards, to see if the IF is near oscillation.

or

just align per instructions.

Though this indeed looks to be more idiosyncratic than
misalignment.

Is the white bar still present with no signal (i.e., just snow)?

Brett: I think you are on to something. It has a flaky contrast set up. I will check it out tonight.

You might try displaying that video line on your scope like in the second picture, triggering on that channel. On a second scope channel probe around to see if you can find a pulse that occurs when the white line does (the jump up in the video trace). That might lead you to where the two signals are combining. Maybe a leaky tube socket.

EDIT: I wonder if it has to do with the DC Restoration circuit.

Doesn't it look like the contrast control in that chassis is basically controlling the gain of the rf and possibly a couple IF tubes, like a manual agc? I think that practice was found to be a no-no pretty early on in the game, and most manufactures opted for controlling the gain of the video amp.

Hm.. since it's manual, wouldn't it be mgc 'stead of agc? Just messin with ya. :D:tongue:

Good catch. :D

More testing.....
If I pull the signal off the antenna input, the white bar goes away. Only snow appears on the tube.
If I tweak the horizontal hold so the picture unlocks horizontally, the white bar stays in place and does not track the horizontal sync bar. See photo.
Again, when a direct video signal is applied after the detector tube to the video amp, the picture looks great and there is no white line.
Bar only appears when video off the detector feeds the video amp.
Since the white bar does not track the horizontal sync pulse, I am now really confused. I originally thought the white bar was part of the picture as it does show up that way on the scope, but looking at the photo I took off the CRT, the picture information is separate from the video image.

This does make sense if you understand that the black bar is always part of the video. The black bar is where the horizontal video sync input pulse is in the video signal. The white bar in your case IS coming from the horizontal sweep signal, it always is at the start of the sweep. Looks to me that part of the horizontal sweep sawtooth signal is getting into the RF-IF-Detector area.
Are there sweep wires (like yoke) near that area?

Exactly. The deflection is is leaking into the tuner or IF stages.

Another thing to look out for is missing shielding on the tuner/IF (especially tube shields) and the HV (is the HV cage installed?). If there are any B+ lines shared between the horizontal stage and the tuner the filtering on those is suspect.... may want to check for heater-cathode shorts in the tuner/IF and the horizontal stage too.

What is the actual signal source you've got going to the antenna input?

For a Signal Source I have used both off air signal from a VHS Deck modulator on Channel 3 and a also a Leader LCG-396 NTSC Pattern Generator.
The HV cage is installed.
Only one tube has a shield and that is the tube at the very front end of the tuner. Does anyone know if this set came with tube shields?
B+ is not used in the IF circuits. Only used in vertical output stage from what I can see on the schematic.
No Yoke wires in this area of the IF strip.

The IF has to be supplied positive voltage from some B+ rail of some type or it wouldn't pass any signal at all...

If the schematic happens to use the archaic B+, B++, B+++ notation to differentiate the different B+ rails know That I wasn't referring to the B+ rail specifically but to all positive supply rails categorically when I used B+ in a previous post (and I generally refer to it categorically in most posts I make). If any positive rail is shared between the tuner/IF and the horizontal sweep/sync separator that could be a leakage path for the noise you see.