Back with a 630-TS Problem

[Chris K]

Hi all. Good to be back. Life got really, really "lifeie". Re-configured the shop as well. Just got overwhelmed with TVs, parts and junk.

I'm working on the granddaddy of post war RCA TVs. The horizontal is completely unstable, "twitching" almost like something is intermittently arcing although I can't hear or see anything. It won't lock. C168 on the phase can, value 153, has been replaced in fact, EVERYTHING in the horizontal circuit has been replaced. I guess the first thing I should do is check for cold joints. All the tubes in the horizontal circuit have been replaced multiple times with known good tubes. Any suggestions as to where I should start?

BTW, just for anyone who remembers my issue with the T-65, KCS47 and the bent hourglass sides, it was the yoke swap I did. The original yokes are back in place and it's got a rectangular picture. Not magnetized.

[Yamamaya42]

The synchrolock circuit is a very fussy beast to tame!
When it works, it works very well, but when it misbehaves, It's a real bitch! :/

[Chris K]

Yeah I can't even get a solid sawtooth for the horizontal frequency. I can get it to 15.75 KHz then it jumps all over the place and the trace goes haywire then it holds for half a second etc. Like I said, it strikes me that it might be an intermittent connection although all the coils ohm out so I think cold solder joints is where I should start.

[old_tv_nut]

No experience with the synchrolock circuit, so can only make ignorant comments:

1) I'd look for cold solder joints too, but not expect to find any if I had replaced all the parts

2a) Any possibility of having a replaced part value with the decimal point in the wrong place?

2b) Does anyone know of parts value mistakes in schematics depending on the source?

Edit: 3) is there a way to break the loop (like grounding the phase detector output) to see if the oscillator is stable or jumps around by itself?

[Yamamaya42]

There's an EXACT adjustment for the adjustment for the horz osc, in the SAMS, was that followed?

[DavGoodlin]

I have a similar issue with a 630 TS horizontal sync pulse getting lost before going to the oscillator.
Been sitting for months waiting for a fix after complete recap.
I'm working on it for another VK member who has a Philco 65 roundie for me as compensation.

First step is to check your work, one cap off by factor of 10 or to wrong spot can cause mayhem and we all have done it.

Synchro-guide is explained in RCA literature (can supply some if needed) and re-reading it may help both of us.

I'm enlightened by Wayne's last comment above; grounding a feedback loop can give a clue if oscillator itself has good output waveshape, part of adjustment procedure noted. (have a scope?) This may help uncover source of unstable operation.