I notice that there is some vertical foldover at the top of the raster.
The Sams says check 12BH7 VOT.
One side checks ok and the other is in the yellow ? range. Could this be the cause.
The ion trap was right where it should be which means low HV or weak CRT (maybe it needs to "cook" for awhile)



BTW I think I figured out why the tube was glowing blue. I had swapped the 6SN7 osc tube with another one from the set. Maybe the oscillator is picky?.

Status of the set.
I replaced the 12BH7 vert, output tube to no effect. Still has foldover.
There is sound getting trough and I presume video but there is no sync.
Horizontal hold is at the one extreme there is maybe 10-15 horizontal lines.
Turn it too far the other way and HV cuts out and it makes unhappy noises.
Vertical hold appears to keep rolling as well. I have replaced the sync separator tube with another one with no effect.
I am guessing that I should check the voltages on the 12SN7 sync separator?

I have gotten the set to display a picture.
The only thing is that it will not lock on powerup, you have to adjust the horiz, hold.
It seems there is some component that will not allow the set to lock when cold until it warms up after about 2 minutes.

Is it just the horizontal that is unstable? If so shotgun the resistors and mica caps in the horizontal oscillator, Horiz. AFC and any feedback from the fly. If not do the same for the sync section.
It may be a good idea to adjust the AGC (if present first).
If you rather troubleshoot than shotgun, I recommend getting a can of freeze spray letting it warm up and stabilize then start spraying things with it running. The part that makes it flake out when you cool it is the problem.

The set seems to have quite poor horizontal lock.
I have borrowed a HV probe from a friend and it seems to measure a little over 10kV maybe 11kV. The top half inch or so of the picture when locked seems to pull to the right gradually getting worse, eventually the horizontal lock is lost. Vertical is rock solid. Should I go on a witch hunt in the horizontal oscillator section.

Probably. Your not using a VCR as your signal source correct?...VCRs often will cause bad horizontal tearing at the top of the screen on tube era TVs.

Actually, I am using a vcr.

I bet the VCR is at least part of your issue. Try a DVD player. It's OK to use the VCR with the DVD as the problem only happens when you play a tape.

I tried hooking the TV up to a Super Nintendo game system via the composite out and the horizontal lock was solid. No tearing. Now there is a new problem I just noticed. there is a "flag waving" effect in the picture. The left and right edges seem to ever so slightly wave back and forth like a flag.

So the width narrows and widens differently as you look up or down the screen, and the whole effect rolls up or down the screen right? On rect color sets that is called pincushion...On monochrome sets that is called bad electrolytic caps or insufficient filtering.

The left and right sides are straight.
The effect is very subtle, you only see if if you look for it. All electrolytic capacitors are brand new from nichicon. Could I try moving the video wire of the crt away from the rest.

Well I spoke too soon.
The dreaded horizontal issue is not fixed by not using a VCR.
It would seem that the horizontal oscillator is running off frequency, being that the spot where it locks is at one extreme of the control. I switched out the horizontal osc tube for another one and it just made it worse (new tube checks good), there was different sounds and it was so off frequency that the high voltage died when you turned the hold control.
Should I try and get a hold of a oscilliscope?

What I would do is put back the good tube, get the hold as close to center as you can then adjust the H osc transformer/coil to re-sync...If you can't get the front control to center you may have to alternately walk the pair. There is often two adjustments on the osc. can one is for stability. If the service lit lacks a non-scope method of adjusting the osc. then it may be a good idea to get a scope on it.

I tried what you suggested. I think that made it worse, there is now no point where it will lock the picture.

You have to follow the horizontal osc coil proceedure, per the schematic. The set also uses the horiz phase detector circuit, another 6SN7 next to the 25L6. Check around that area. :scratch2:

I feel really mad.
I managed to break the fine tuning shaft.
The shaft is broken where it connects to the little plate in the back.
Does anyone have a spare tuner or a way to fix it?

I fixed the fine tuning shaft.
I also replaced the two 150k feedback resistors from the flyback.
They had drifted up to 195k each.
No change.
Should I check more resistors.

I have purchased a Eico 460 oscilloscope. I have restored it and built a 10x probe.
Can I connect the ground lead of the scope to the chassis? The chassis is connected to a isolation transformer.

Fine, as long as it's connected to an isolation transformer.

I have scoped out several waveforms in the horiz, osc section and they don't really match the schematic.
The waveform on pin 1 of the 6SN7 multivibrator looked squished vertically and the general
shape did not look right. Is it better to start at the sync separator and go towards the oscillator or vice versa?

Here are some of the waveforms I got with the picture locked.
Sync phase inverter (12SN7, pin 4)
Attachment 194193
Horiz, AFC (6SN7, pin )
Attachment 194194
Horiz, multivibrator (6SN7, pin 6)
Attachment 194195
After I got these I tried to check the waveform on pin 1 of the oscillator tube.
When I connected the scope probe to that point the lock just disappeared completely.
Is that a clue?
Ignore the 2 dots in the pictures, its a reflection from the ceiling light.

I think I have found the root cause of the problem.
Video noise on the sync signal. When you turn up the contrast there are various points on the right side of the screen that pull to the right. But when the screen is black, it goes away.
I will be doing some more probing with the scope to find where it is coming from.

The video noise appears on the power supply.
It goes away when the video output tube is removed from circuit and connect to the filament string with clip leads.