Back under my 730TV1 this past weekend.

http://i1075.photobucket.com/albums/...psrvcomorr.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/...pspbsroj75.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.

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 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.

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.

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/9/8890/1...809c5d4f_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/9/8799/1...c8f40a7f_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