I posted a question about this set on another thread but I figured I would make a thread for the set and keep it all in one place. This is my second ever restoration and it is going 100 times faster than my first. I've recapped the chassis, fixed a problem with the flyback, and replaced the megohm resistor between the HV rectifier and the crt anode that had drifted WAY high. To my delight the set is producing a picture :banana:. My next hurdle to tackle is a vertical linearity problem. I'm going to go hunting in that area for any out of spec resistor and check the height and vertical linearity controls for spec. There is a video link below that shows off the problem very well.
http://www.youtube.com/watch?v=zK56_BK_7vA&context=C2c47eADOEgsToPDskLBVGQ_GYMFlODWfOTpscLd

Hmmm... can't easily see a vertical linearity problem in your video. That's much easier to see with a test pattern.

Things to look for:

- drifted resistor values
- wrong capacitor values (double check your replacements, and don't use ceramic disks)
- weak tube
- bad potentiometer

Yoke or vertical output transformer issues usually have more severe symptoms, although I have seen a case of a leaky vertical output transformer (leakage between primary and secondary) which caused subtle problems in the vertical system.

It is much easier to see with the test pattern below. No time tonight for poking around under the chassis but I thought I'd post a picture of progress so far.
http://farm8.staticflickr.com/7153/6513264441_38c297496d.jpg

My next hurdle to tackle is a vertical linearity problem. I'm going to go hunting in that area for any out of spec resistor and check the height and vertical linearity controls for spec.

Using the numbers from the Sams on

http://www.earlytelevision.org/tv_schematic_diagrams.html

A logical order to test:

Check or substitute V14.

Check voltages on V14A & V14B.
Note: Remember that on this tube you are not measuring to chassis.

On V14B:

Check C58, C57 for leaking, if replaced check for correct value and for leakage.

Check R67 for correct value.

And the two electrolytics, C2 and C1, check by jumping.

Also jump C3 across the height control.


My best guess is that the big fat C58 going from the vertical osc. plate to the high resistance grid of the vertical output is leaking.

C58 originally was only a 200 volt, I'd go at least 600 on this one, as a little leakage here can give the vert output a very hot plate.

C57 originally was a 1000 volt.

James.

Looks to me like you have a horizontal width problem, not a vertical linearity problem...??

Looks to me like you have a horizontal width problem, not a vertical linearity problem...??

John,

You are 100% correct!

With only the image of the test pattern visible and the height stretched, I had assumed that the RCA roundie was flipped on its side for under-the-chassis checking, but a quick enhancement of the picture to see what is hidding in those shadows reveals that this is not the case.

Let's see if I can undo my rather large goof.

On page 24 of the Sams, you will see the horizontal adjustments.

I would suggest checking or replacing your 6BG6 and then trying (count your turns so you can undo any changes) adjusting the horizontal linearity and see if that helps. Warning: These linearity coils sometimes freeze with age and if forced, you can break the tube. I would suggest a gentle test wiggle with the power off, so you can feel if the core is stuck or not.

If this adjustment seems to be addressing the right problem, and you have recapped and and tested all the tubes in the horizontal section, you might consider doing all the procedure on page 24, with this warning: A mistake in doing the horizontal oscillator adjustment can sometimes be very difficult for a learner to resolve.

James

I think it is me that made the rather large goof, not you James. I thought the picture was stretched vertically so I misdiagnosed the problem as vertical linearity. I did not recognize that the picture could instead be squished horizontally, and therefore a horizontal problem. Interestingly enough when I adjust the width, as well as the horizontal linearity slug there seems to be no change to the picture. Both turn easily and were not stuck at all. The horizontal linearity coil looked a bit melty from the start and I suspected it might be problematic when I first laid eyes on it.
http://farm8.staticflickr.com/7030/6522274419_04312ecfe7.jpg

Width Controls seem to vary in sensitivity from brand to brand, set to set, etc.

The RCAs that I own of that same vintage (721TS, 721TCS, 630TS) seem to need quite a few turns of the Width Control before you get any change.

Now, my 1950 Zenith 12" Porthole, with the Width Control on a slider, is way more sensitive. You breathe on it and you get a change.

Width Controls seem to vary in sensitivity from brand to brand, set to set, etc.

The RCAs that I own of that same vintage (721TS, 721TCS, 630TS) seem to need quite a few turns of the Width Control before you get any change.

Now, my 1950 Zenith 12" Porthole, with the Width Control on a slider, is way more sensitive. You breathe on it and you get a change.

I'll give width another shot when I get back in front of the set.
Thanks for the first hand knowledge, it makes things easier and less scary for sure.

Don't be scared by a little bubbling on the wax around the coil. The big question is whether the windings have continuity and whether the adjuster has any effect at all.

Horizontal linearity is one of the more difficult things to get right on certain TVs (difficult for me, anyhow). Your linearity is noticeably off when viewing a test pattern. I doubt it is half as noticeable if you are simply watching a movie or TV show.

I would follow the instructions in the manual, as suggested, and then see how it looks.

Phil Nelson

I suspect that all that is wrong is the 6BG6. Try substituting a new one.

On page 24 of the Sams, you will see the horizontal adjustments.

A mistake in doing the horizontal oscillator adjustment can sometimes be very difficult for a learner to resolve.

James

You aint kidding!
Gosh did I get my self in trouble while trying to go through the oscillator adjustment. The width is much closer to being correct but I've completely destroyed the picture in the process.
I've given up for the evening because I started to get frustrated and will pick it back up tomorrow. An opportunity to learn oscillator adjustment thoroughly through thoroughly messing it up :).
Edit: I have three horizontal output tubes, the two that tested good gave me pretty much the same results, another that I was unsure of gave me a severely degraded picture.

Coming back fresh made a big difference. I dialed in the horizontal and figured out my problem. This is my first round screen set and I didn't have an idea of what the final picture dimensions should be. I measured the bezel on the cabinet and realized that I had the picture stretched out WAY too far vertically. After I dialed back the vertical size the picture became much more linear. It's still not perfect towards the top of the picture (as you can see by the clock at the top), but it's close enough for me to watch some movies on it and put it back in the back of the restoration cue and move on.
http://farm8.staticflickr.com/7162/6546644389_1653b358a6.jpg
I installed the chassis into the cabinet and now my favorite TV in my collection is a working TV :banana:.
http://farm8.staticflickr.com/7170/6546682687_9b0c0af10c.jpg

That set looks scrumptious, and so does your avatar! :yes:

Your set looks great. I can't really tell from the clock in your picture that the vertical linearity is off by much.

Back under my 730TV1 this past weekend.

http://i1075.photobucket.com/albums/w438/vts1134/38DEADAF-49DF-45E3-9DE9-283E6F97619F_zpsrvcomorr.jpg

I had a problem with the horizontal on the set. As the set would warm up the horizontal would drift which would require an adjustment of the horizontal hold. Eventually, 1 to 1 1/2 hours of use, I would run out of room on the hold control and the picture would fall out of sync. This is our only TV in the upstairs living room and on the weekends we definitely need more than an hour's worth of viewing time, and it's a pain to have to adjust the controls every 15 to 20 minutes.

I replaced a very out of spec resistor in the horizontal oscillator circuit, but after repeating the horizontal alignment procedure it again drifted after 45 minutes or so. I then (and I can't believe I didn't start here) swapped the horizontal oscillator 6SN7 tube with another one in the set. I fired the set up without doing the alignment procedure and let it play. It was rock solid with no drifting in the horizontal for an hour or so. I had to turn it off at that point as I was ready to head to bed. I'll fire the set up again tonight and see if it makes it past the two hour mark without the need to adjust the horizontal control.

That is the way of restored sets that get lots of use. My 1971 Zenith has been a near daily use set for nearly 5 years, and every few years it needs new horizontal deflection tubes, or chroma osc. tube..... This is the phenomenon that is reason why we find sets with original caps, and resistors, but several replacement tubes.

The Horizontal problem was solved with the new 6SN7 in the horizontal oscillator. Lesson learned and I think I'll start with tube replacement in an offending circuit from now on when a problem rears it's head. Always go for the low hanging fruit first :yes:.

Since the chassis was out on the bench I decided to give it an upgrade with a new CRT, and elected to try a 10FP4 in the set even though it's not OEM spec. I was hoping for a nice bright image for daytime sports viewing. The 10FP4 definitely doesn't disappoint in the brightness department, and not having to worry about ion-trap placement was a plus. While I was at it I thought I would, with the help of every one here, take the opportunity to learn a bit more about the set and what might be causing different problems.

The photo below shows the set with the new 10FP4 installed. I've highlighted four problem areas. Can any one help identify what the problems are, what may be causing them, and what (if anything) can be done to solve them?

1- Ghosting
2- Vertical Linearity
3- Focus*
4- Horizontal Linearity

http://i1075.photobucket.com/albums/w438/vts1134/730_zpspbsroj75.jpg

*I believe the new CRT is a rebuild as I can detect a neck weld point when the light is just right. The 10BP4 I had installed previously did not have this focus problem, although that may be simply a coincidence.

Well I've got the focus problem figured out. The focus coil needs to be adjusted beyond what the mount will allow. I guess the 10FP4 and it's straight gun is just different enough that it needs a different angle on the focus coil. I'll modify the mounting holes so I can position the coil where it needs to be with the 10FP4. I'll have to hold off until the chassis is back in the cabinet as the CRT will be in a different position than my temporary out of cabinet support.

Now to tackle the next problem, the ghosting. Does anyone have any thoughts on what could be causing it?

*Edit
I haven't yet tried the tubes in the IF and video sections yet so I'm going to start there and see if that is the culprit of the ghosting.

Now to tackle the next problem, the ghosting. Does anyone have any thoughts on what could be causing it?

.

It is the IF alignment.

It is the IF alignment.

You can test whether the alignment or the video amplifier is responsible for thr ghosting. Simply rotate the fine tuning control and if the ghosting changes, then it is the IF amplifier. In the nearly 70 years since the set was manufactured, the alignment will change. Especially, when in the past, a phantom tweeter likely intervened.

a phantom tweeter likely intervened.

A what now? :saywhat:

A what now? :saywhat:

The "phantom tweeker": a past individual who had a passion for adjusting things which did not require adjusting. On the other hand it could be a bad tube or the coil adjustment drifted as it aged. Obviously my auto correct did not know what a "tweeker" was.

Nevertheless you should make the fine tuning test for the ghosts.

The "phantom tweeker": a past individual who had a passion for adjusting things which did not require adjusting. On the other hand it could be a bad tube or the coil adjustment drifted as it aged. Obviously my auto correct did not know what a "tweeker" was.

Nevertheless you should make the fine tuning test for the ghosts.

Most times I've heard it mentioned here it was under the name 'screwdriver drift'...

I'm glad I don't have auto correct sometimes....Someone on AK has the rather humorous signature line "Dear auto correct, I'm sick and tired of all your Shirt."

Before doing alignment, I would try subbing the IF tubes, beginning with the last one. But watch out for tweeters though.

:D

Phantom Tweeker makes much more sense :yes:.

Adjusting the fine tuning does change the ghosting somewhat, and at one end of the control the ghosting is actually doubled up so the image is tripled. As I adjust the fine tuning I also have to adjust the picture control due to the changing signal level across the fine tuning range. I could post a video to show the behavior.

As per old_coot88's advice I am going to procure more 6AG6's to sub in for the IF tubes to see if that makes a change. I'm secretly hoping it wont as I eventually need to learn IF alignment and I may as well start with this set.

The Horizontal problem was solved with the new 6SN7 in the horizontal oscillator.

Wrong :no: :tears: :thumbsdn: !

Sad to say this was not my problem. I let the set play on my bench for a couple of weeks every night for a few hours with zero problems. I thought the problem was licked until I re-installed the chassis into the cabinet and the problem reared its ugly head once again. I couldn't believe it :sigh:. So once again I hauled the chassis downstairs to trouble shoot. Again if I play the chassis in the open cool basement air it will go for hours without a problem. What I had to do was give it a "cabinet" to get things heated up.

https://c1.staticflickr.com/9/8890/18045741270_db809c5d4f_z.jpg

This did the trick and it displays the same symptoms it does upstairs in its cabinet. As the set heats up the horizontal drifts requiring an adjustment of the horizontal hold control. Last night I had it on for three hours and it needed to be adjusted at one hour and at two hours. It probably would have needed adjustment again if I could have stayed awake longer. It's not so much of an inconvenience to have to "bump" the control every hour when watching the set, but the drift never stops and eventually I run out of adjustment at the end of the control making the set un-watchable.


I have replaced C65 and C66 with no change. I will try C59 next. I have swapped V15 twice with no effect. All of my resistance measurements are within spec at V15. I'm kind of at a loss.

https://c1.staticflickr.com/9/8799/17612812583_fcc8f40a7f_z.jpg

Could be a resistor too..... Turn it on and use a soldering iron to warm up a few
parts quicker than what an hour would take.... But be aware too much warming
may make a good part look bad....

I wonder if your odd linearity problems are related to the focus coil.....
I don't ever recall seeing vertical linearity different on the right,
and left sides of the screen at the same time... That looks like
stray magnetic fields..... Maybe the gun is not put on straight....?

.

If you can get ahold of a can of Freez Spray aka Circuit Cooler (RS still sells it AFAIK), let the TV get thoroughly warmed and into the fault condition (a blanket over it speeds it up). Then hit each component with the spray. It's almost guaranteed to pinpoint the drifted part.

I had a set do the exact same thing. I started with a heat gun to speed up the failure and isolate the area and the a soldering iron and freeze spray to narrow it down to a tubular ceramic cap that would be the equal to your C59. Changed it out and all is good.

Gregb