1963 Zenith 29JC20 restoration
 

I picked up this Zenith 29JC20 last week at the Richmond Antique Radio and TV museum estate sale. My hope is to restore the set and use it daily. Here are some pictures of it before I get started. It's PVA has started turning green. I may attempt the cataract removal process if it affects the picture much. The cabinet is a little rough but not too bad. The service tag (PSI?? weight??) lists a bunch of service in the late 60's. The Picture tube is a 21FJP22A rebuild dated late 1973. Looks like its got the same tie-strap around the cloverleaf that I read about on other 29JC20s. Looks like some recent replacements of a few capacitors with orange-drops and only two small electrolytics. First I will check the picture tube with my slightly flakey CR70. Then I plan to shot-gun the old caps, the electrolytics, replace all the off value resistors, check the coils, and replace the bad tubes before I power it up. I am curious how this narrow band chroma set with RE phosphors looks compared to my 21CT55 with its 21AXP22A (my avatar/signature).

My very first concern with that set would be the integrity of the plastic/(nylon?) coil form of the H efficiency coil, which tends to crystalize over time and fall apart. If that happens, the requisite 'dip' in cathode current of the H output tube is lost, allowing the current to soar 'waay over spec.

Very nice.. These Zeniths seem to be popping up lately.. I wonder how the CRT is..

I'm going to be getting one in a few weeks, so this should be an interesting thread.

I'm guessing that the tag *actually* belongs on a fire extinguisher. :scratch2:

Picture will be brighter for sure, but will you enjoy the colors as much as your wonderful 21CT55? Be interesting to see side-by-side photos when you are finished restoring the Zenith.

jr

Zenith sets do tend to have rather sharp monochrome detail, focus, and contrast...It can be so good that one can still think the picture looks good with moderate tint and gray scale miss-adjustment....Granted later roundys and rectangular Zeniths are what I'm familiar with. The only RCA based set that could hold a candle to it is my CTC-4, but the 4 don't get good color at the same fine tune point as monochrome, and the sound is best at a third spot so it could be an alignment fluke.

At the moment mine is still intact. Is there some way to visibly see that it is crystalized? On other sets where the ferrite cores have been tight, I have let them soak in a little WD40 which seemed to ease their movement. Any suggestions for this coil?

I used a hair dryer to loosen them, then some gentle prodding with the twiddle stick is usually all it takes.

:banana: Apparently the CRT emissions are good! :thmbsp: I coaxed my CR70 into working. My CR70 was tripping its power switch/breaker when I had this CRT plugged in and all set up. I found that turning the filament range setting all the way down, switching it on, and then bringing up the filament adjust to the 6.3V kept the switch from cutting out. Guess I should re-cap the CR70? Anyway it showed good emissions on all three guns, even with 5V on the filaments.

I am guessing that the more narrow chroma bandwidth will just mean a lower color resolution than the wideband 21CT55. It interesting that the current crop of 4K displays are using this same high-res luminance + lower-res color to lower the bandwidth to allow HDMI 2 to drive 4K:
http://hdguru.com/hdmi-2-0-what-you-need-to-know/

I think its based on the human eye seeing B/W in higher resolution than color.

Dave

I will definitely give that a try. Gentleness counts on these old sets.

Dave

From the photo, it looks like the coil form is phenolic. If so, you're in luck. The whitish, semi-clear plastic forms are the ones that crystalize.
If the three blue adjustment coils on the convergance board also have phenolic forms, you're doubly in luck.

That's exactly right. That's why earlier hi-resolution chroma was fudged to simply 'paint' color in the BW image.

Yes the convergence board coils also look the same. From a couple of tags on the set I think it was made in 1963. Maybe Zenith changed to phenolic coil forms by then.

It is the other way around. The phenolic forms are the old type, and Zenith moved away from them to the notorious plastic forms that they had from the mid 60's to the late 70's.