630TS Lost the Vertical
 

OK guys. I've been asked to look this chassis over and see if I can find the problem. Well I can't.
The background is that it has been recapped and some of the resistors have been replaced. It did have vertical when first tried but then lost the vertical soon after. The Vertical Centering pot does move the trace up and down. The Vert. Lin. pot has little effect.
Here's what I did so far.
1) I checked out the Vert. Osc. and the Vert. Output transformers. Both ohmed out good.
2) I ohmed out the yoke and it checked good.
3) Checked the tubes in the Vert. section along with the tubes in the Sync section. All tested in the good range.
4) Traced all the components in the Vertical section to see if they went where they were supposed to along with their values. All looked good.
5) Checked and cleaned both the Height and Vert. Lin pots. Both checked good on the ohmmeter.
6) Did a through visual for shorts, solder blobs, etc.
7) Tapped on the chassis some but that didn't help either. :>).
Here's a picture and then a video of the situation.
Any ideas guys?

https://tvrestorerguy.com/wp-content.../100_0184a.jpg

And the YouTube video:

https://youtu.be/RyM6xCjcXiY

What about the hold pot ?

Yeah, that ohmed out good. It was cleaned too.

Got scope? Checking the waveforms against the schematic (if sams that early have waveforms) should reveal issues.

Another method is to connect the heater to the output tube grid...That will inject a 60Hz signal and give the output some drive. If the output works with injected drive then you can also do the same at the osc. grid to check whether the isue is in the coupling between osc and output or a lack of oscillation.

Better to couple it through a cap. Value not critical, .047 - .1 mf or so.

Guys,
I coupled the grid of the output tube to the heater and then did the same for the OSC. tube. I used a .047 cap as suggested.

The first picture shows without any heater coupling to the grid.
The second picture shows the Output tube.
The third picture shows the OSC. tube.

https://tvrestorerguy.com/wp-content.../100_0189a.jpg
https://tvrestorerguy.com/wp-content.../100_0188a.jpg
https://tvrestorerguy.com/wp-content.../100_0187a.jpg

Looks like when the heater is coupled to the grid of the OSC. tube I get the most Vertical.
I'm puzzled. I thought it would be greater vertical with the Output tube coupled.

I'm not electronically adept, but just wanted to chime in that when I acquired my restored 630 I had a heck of time getting the rear adjustments just right. It took a careful tweaking of all controls to keep the picture centered and steady. The "sync lock" thumbwheel control was particularly touchy. Once set it's been fine.

Joe,
Where is the "sync lock" thunbwheel" control?

It's on the rear chassis with the other controls. It's the small thumbwheel control that is positioned slightly higher than the rest of the controls. I believe towards the middle, right above the antenna input panel.

Where is this sync-lock control in the circuitry?

If I'm not mistaken that sync control is an aluminum square can with the adjusting screw in the center. I don't think it's on top it's on the under side of the chassis .

Yes... horizontal frequency slug B2, and the terminal strip below is "sync link"

jr

Vertical oscillator blocking transformer?

The control I was mentioning is on the back of the chassis directly above the antenna terminals. It's a thin control shaft with a thumb-wheel end. Here's a pic from the Net where you can easily see it:

Sorry, the antenna terminals are in the upper left, above the power transformer, the terminal strip by the ul sticker is the "sync link" strip, see my previous post.

jr

My bad- I don't have easy access to the back of my set. No, not the antenna terminal. It's above what looks like an antenna terminal near the center of the back the chassis.

Well maybe. It did ohm out good. I have another NIB that I thought I'd try to see what happens.

Primary to secondary leakage in the blocking trans could cause bias issues...Shorted turns could detune the frequency and suppress oscillation. Did you compare tube/schematic voltages in the vert stage yet?

Blocking xfmr was my first thought, once he got sweep by injecting at the osc. grid.

It was the blocking transformer! I had another one here and put it in. Bingo!
Thanks for all the suggestions.

:banana::banana:

:thmbsp:

Can you measure anything odd on the bad transformer? Seems as if we have seen several now that have appeared to be good, but did not function. :scratch2:

jr

I measured the leads each other and to the case. Everything seemed good. I then hit it with my heat gun and got this:

https://tvrestorerguy.com/wp-content.../100_0196a.jpg
https://tvrestorerguy.com/wp-content.../100_0197a.jpg

Yup, a transformer! I ohmed out the windings again and the values crept up from pri-1130 to 1533, sec-153 to 173. I also checked for shorts between the leads and shorts to the core. All seemed good.

Wondering if a shorted turn could kill AC operation, but change DC ohms only a tiny amount, so undetectable with an ohmmeter?

That's what I'm thinking. Or there is some leakage that won't be measurable with a low voltage ohmmeter. You'd need an insulation tester - AKA "megger"

Well now after getting a decent picture with direct video injection, I can't get a good picture through the antenna terminals.
So I replaced the resistors in the IF stages. The caps were previously replaced. Still not a good picture. I get decent sound though.
So I tried a quick alignment but the signal was very small going through to my VTVM. When I made an adjustment the needle moved just a little bit.
After that I tried it again. No joy. Here is the picture I get of a test pattern. You can see it is there, it just isn't very good. The tubes were tested and they are good.
Any ideas? Thanks.

https://tvrestorerguy.com/wp-content.../100_0246a.jpg

Looks like some sort of regeneration (?)
Is this what it looked like before you attempted alignment?
It helps others to help you if you show a picture of the problem before you try to fix it.

Are all tube shields in place?
Could it be an AGC problem?
Sorry for a dumb question, but did you completely disconnect everything you used for direct video injection?

Yeah, the same thing before the alignment.
All shields in place.
Everything is disconnected.
Actually the same thing before I replaced all the resistors too!

Warning: I would wait for more comments and ideas from others who have worked on this chassis, but here's my 2 cents anyway.

I forgot there is no AGC, just manual Picture control - I would check the voltages and operation of the control.

Also maybe a bad bypass cap in the IF (all those 1500 pF caps).

Good operation with direct video injection rules out anything after the injection point.

The 1946-48 630 chassis have a reputation for bad mica caps in the IF...One of the only cases where I advocate recapping the micas.

Yes, I replaced those micas and the one coming from the tuner.

Might be a good attack to take a spare 1500 pf and bridge the replaced ones one at a time. (?)

The micas in the IF stages are all 270pf. Are you saying to bridge each one with a 1500pf one?

Sorry, I meant the 1500 pf bypass caps that are everywhere. Did you replace any of them? If not, that is even more reason to look for trouble with one of them.

OK, that makes sense. None of those were changed. There's a bunch of them. I'll let you what I find.
Thanks.

OK, I jumpered each 1500pf bypass cap with some clip leads attached to a 1500pf mica cap. It wasn't as hard as I thought it would be. Still no joy. I'm suspecting the tuner.
Anymore ideas I could try?

Even though the IF tubes test ok, I would try swapping them out to see if the symptoms change. :scratch2:

jr

:thmbsp:

I take it you found no hot spots that changed the behavior when touched.

How does the picture react as you turn the Picture control up and down? Do the streaks move? Or is there only a contrast change?

Another question: what do you get if you disconnect the input signal? Can you get snow without streaking?

OK, I swapped out each one, one at a time with another NIB RCA 6AG5 that tested like new. Still no joy. Basically the same with each swap out. Good idea though.