1971 Philco color Tube Hybrid

[Lain94]

Here are some photos of the schematic, I have used my oscilloscope to check various points, so far I have concluded the burst amp transistor is ok as well as the 3.58mhz oscillator IC based on the waveforms I got. I am suspecting a bad or out of tolerance crystal at this point and already ordered a replacement one of the appropriate case size and power rating. We will see if that resolves this color being out of sync.

https://imgur.com/a/ZgjkHZm

[old_tv_nut]

If the oscillator is running but won't sync, I suspect the crystal is OK and something else is wrong. It appears that D98 (or D96, hard to read) (between R124 and the IC) is a varactor diode used to control the oscillator frequency. I would check it out.

[old_tv_nut]

Have you checked the diode? I'd like to know if my guess was wrong or not.

[Lain94]

Diode will be checked next, crystal replaced and issue persists albeit not as severe. I am thinking this could be simply a matter of adjusting the 3.58mhz oscillator inductor.

[old_tv_nut]

Originally Posted by Lain94

Diode will be checked next, crystal replaced and issue persists albeit not as severe. I am thinking this could be simply a matter of adjusting the 3.58mhz oscillator inductor.

You mean you haven't tried adjusting it yet?

[old_tv_nut]

Does the service info give an adjustment procedure? It looks to me like there is a tuned output transformer that may or may not have much effect on the oscillator frequency depending on wha the internal IC output circuit is. Is that coil mentioned in the procedure?

[Lain94]

Originally Posted by old_tv_nut

You mean you haven't tried adjusting it yet?

I later ended up trying to adjust it but to no avail, all it seems to change is whether or not the rainbow barber polls pattern is in motion or not. I will be revisiting this project soon as I had to put a lot of things on hiatus last year but will be going on a marathon of sorts later this summer and I am aiming to get the Ford Philco color sync issue resolved hopefully soon.

[Lain94]

Originally Posted by old_tv_nut

Does the service info give an adjustment procedure? It looks to me like there is a tuned output transformer that may or may not have much effect on the oscillator frequency depending on wha the internal IC output circuit is. Is that coil mentioned in the procedure?

From what I have been able to deduce there is a varactor that is controlling and automatically adjusting the oscillator frequency in parallel with the oscillator itself.