It's almost certain that will be a bad Lytic(s) in the Vertical circuit.

There are usually several attached to the vert osc/output tube and that is a classic symptom.

The vertical height and linerity controls will fix small problems but that is severe!

Strange, many old sets will fire up and work to some degree but the Vertical is the one thing that is always messed up :dunno:

Wow... is that Lucy??? She's a little down in the mouth! :p:

Yep,
Bad electrolytics in the Vertical section. 3 resistors also needed replacing. Looks great now! The audio is very clear. It's nice Zenith put the buzz control on the back of the chassis instead of under the CRT like in the 1950 model. Still have some work to do on the Radio/Phono. Stay tuned.

Jim

You'll want to look in the Vertical Output circuit for the cause of the nonlinearity in most cases. The Vertical Linearity control will correct minor nonlinearity but it's a sign of circuit trouble if the control has to be turned too close to either extreme to get a good, linear sweep or if the control reaches the end of its rotation without fully correcting it. Electroytics are most often to blame and there are a few around the oscillator and output stages for decoupling and bypass. You've got full height, so I would say the waveforms' amplitudes should be close to correct unless the Vertical Size control has to be cranked way up. Good vertical locking indicates that the oscillator is able to synchronize correctly. Also check any waveshaping networks for an out-of-tolerance resistor or cap. If you haven't replaced all the paper caps in the vertical section, one of those could be part of the problem, but electrolytics are the most likely culprits. Vertical output amplifiers are basaically single-ended Class A audio amps designed to have very low distortion and optimum low-frequency response.

Porthole Progress
 

I finished replacing all the electrolytics today. Very good vertical locking, Never flips or rolls. Just watched Rita Hayworth in "Gilda" and everything looked great even the TV.:) The only oddity left is getting the picture to lock in when the set is turned on. I always have to give the horizontal hold a slight turn to lock the picture then everything is fine. I waited a full 3 minutes when First started to see if it just needed to warm up but no luck. My 1950 Zenith Porthole locks in about 30 seconds after it's turned on. Any ideas?

Jim

Jim,

Once you have the picture locked apply a small piece of scotch tape down at the bottom of the screen where you won't see it. It will hold the picture stable.

Let us know if this works K? ;)

Rob

Ha Ha,
Everyone knows you have to slap the sides of the cabinet and pound on the top or is that a lost art form?

Jim

Not at all Jim, I use that technique on my Computer Monitor all the time.



:lmao:

Latest Project/Brain fart
 

So I'm working on this RCA 2T51 re:http://audiokarma.org/forums/showthr...&threadid=7085

After replacing several caps inside the HV cage the #*&$ thing didn't work anymore :dammit:

I futzed with it for an hour or so before I remembered this set uses an electromagnetic speaker and it WON"T WORK if it's not plugged in :dammit: :dammit: :uzi: :nerd:

Heh heh.. anyway it works again now, the picture is nice and bright after getting rid of the bad resistor and getting some HV to the CRT Anode. :beerchug: Nice and clear too, even with the 8" test CRT I was using.

Only thing now is the Vertical is badly messed up, there is a three section Lytic I haven't done yet and I am pretty sure that will take care of that.

I don't think I'm going to recap the I.F section, it is working great right now so why tinker and screw up the alignment?

The Shelby 2T51
 

Well I've got this set working pretty well :D

I added a page to my Site for it and made a small video.

Let me know what you think

http://www.vintagetvsets.com/2t51.htm

Customer's Dumont RA109 Ready
 

This was a massive project! Lots of circuitry in this set (35 tubes) and it's now fully recapped with a nice and bright used 19AP4. The original dud was going to be rebuilt, but got "aired" during shipping to Hawk-Eye. Obtained a replacement with help from Hawk-Eye. The tuning dial cord on these things is a real fun project to re-string, especially since Sams "forgot" the diagram for the TV/FM dial cord. They have the AM tuner's stringing diagram, but this set didn't have the AM tuner or phono options.

I brought up my Andrea 16" roundie on Saturday. Most of the lytics reformed nicely. The radio sounded great with no hum:D

Now it's time to get caps. One of the lytics in the vertical, I think, is dead shorted (low voltage).

I enabled the HV after reinstalling the 16GP4 and was rewarded with an image. It was nice and bright with washed out video. I know this set will look great after I recap.

Alright, I should have recapped before I brought it up, but the local parts distributer's hours conflict with my work hours.:mad:

If you don't mind vidcaps (I don't have a digital camera or scanner), I'll start filling the gallery.

I think I've got a winner here.:D

Go for it!

1957 GE Television
 

Here's my latest project, A GE 24" Television.
I had to replace 6 "Lytics" and 9 caps to get it back to great performance again. Nice set with a clear picture and the Mahogany cabinet is near mint. Got this one from captainmoody, Thanks!
Jim

Nice set Jim!

:thmbsp: