Motorola 17T21 Flyback & Schematic

[Electronic M]

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.

[Mre12ax7]

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.

[Electronic M]

Originally Posted by Mre12ax7

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.

[Mre12ax7]

Actually, I am using a vcr.

[Mre12ax7]

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.

[Mre12ax7]

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.

[dieseljeep]

Originally Posted by Mre12ax7

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.

[Mre12ax7]

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?

[Mre12ax7]

Here are some of the waveforms I got with the picture locked.
Sync phase inverter (12SN7, pin 4)
IMG_0378.JPG
Horiz, AFC (6SN7, pin )
IMG_0379.JPG
Horiz, multivibrator (6SN7, pin 6)
IMG_0380.JPG
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.