1962/3 Zenith 27KC20Q

[rca2000]

Originally Posted by Penthode

With the documents I received with the Zenith, it appeared two subsequent sets were purchased as subsequent replacement sets: a hybrid GE in the early 70's and a solid state mid/late 80's Capehart . There was no sign of the later sets in the house. This suggested despite newer "replacement" TV sets bought, the previous owner hung on to the old Zenith. I was told by the new owner of the house, the set was hidden away with stuff placed on top hence I do not believe the Zenith was used much at all after the new sets were bought. Perhaps sentimentality and the memory of the hefty purchase price made it difficult to part with the Zenith? Nevertheless the Zenith remained in the same house for nearly 52 years.

I tested the sets original Zenith CRT and there was initially little sign of any cathode emission. Leaving the tube heated for an evening, the tube eventually showed good emission on all three guns. I wonder if there is a relationship how many years the tube sits dormant and how long it takes to wake up?

One way or another...SOMETHING prevented it's demise. And it sat there for all of those years...just WAITING for someone like one of us to come along--who would appreciate it for what it is. In all likelihood--those other sets LONG ago--hit a packer truck..but somehow--the Zenith was spared...

And aren't you glad it was ?

You said-"stuff was on top of it" and so it was used as a "shelf" That MAY be what saved it...

Round color tubes often have decent life after all of this time. Both of the CTC-5's I have ran across in recent years had very good, like new tubes. But my 29JC20 does NOT have a good tube, the red gun is weak--and will not come up. I wonder why--maybe my set got a lot more use--or the tube was defective from the beginning. It will work--but is obviously deficient on the reds.

I do have a JP22 I could put it it that is quite good--but it has been sold. I have one more--in a 24NC31 parts set--a channel master dated 1979 I think--that I think tested good some years ago--and maybe sometime--I will put it in there. One way or another--I am going to pull that tube and all else-- and get rid of the cabinet--I need the room for other sets.

[Tubejunke]

Originally Posted by rca2000

You said-"stuff was on top of it" and so it was used as a "shelf" That MAY be what saved it...

Round color tubes often have decent life after all of this time. Both of the CTC-5's I have ran across in recent years had very good, like new tubes.

I think some of the subjects such as original cost that we have hit upon lend to sets first not being taken for granted as we do today often letting them play around the clock or somewhere close. I remember as a youngster in the 70s that the ONE family set (a 19" Sears Medalist) was only used a few hours a day, and not every day just some days.

It went like this: The housewife watched a couple of hours of soap operas; when we came home from school we watched a few 1/2 hr shows or cartoons. Dad and sometimes mom watched 1/2 hr. local news followed by the CBS Evening News with Walter Cronkite. Then often there were the prime time favorites of the era for a couple of hours.

Again, even then a color TV of any size was an investment as well as (often) a nice piece of furniture, so even when a set developed some problem that deemed it not worth going to the repair shop again, it was kept. Perhaps a table model would go nicely on top of the old console. That happened a lot! I remember about 1981 or so Dad brought home our first console with a HUGE 24" or 25" tube and remote control. Almost unbelievable at the time. We didn't yet know what the funny round antenna thing sticking out the back would be for. That came several years later when they finally ran cable vision out our road.

Was it really that long ago?

[Penthode]

Well, I have pulled the chassis to give it a clean. As I had expected, the plastic on the early convergence clover leaf is shot. The later Zeniths with the bright Red, Green, Blue enclosures seem to stand the test of time but not the earlier open plastic loops. Does anyone have or know where one could get a replacement?

I see that the later Zenith Roundie sets all have the same convergence coil resistances so this would do as a last resort.
Also, the control knobs have crumbled. The plastic seems to crumble on these early Zenith color sets. I'll post some photos. Otherwise the set appears to be in good shape.

I did however find a lot of sticky gunk on the wires. It doesn't necessarily look or smell like a nicotine set. It looks more as if it is cooking grease. (I wonder if the set was in or near a kitchen?) The consistency is thick and it isn't soluble in water: it seems to dissolve with paint thinner. I'll post some photos of this. Any thoughts?

[kvflyer]

Originally Posted by Penthode

Well, I have pulled the chassis to give it a clean. As I had expected, the plastic on the

...

I did however find a lot of sticky gunk on the wires. It doesn't necessarily look or smell like a nicotine set. It looks more as if it is cooking grease. (I wonder if the set was in or near a kitchen?) The consistency is thick and it isn't soluble in water: it seems to dissolve with paint thinner. I'll post some photos of this. Any thoughts?

Most if not all of the plastic wires so this vintage electronics exhibit that. I know that my CTC-9 wires are like that. I believe it isn't kitchen grease; rather the plasticizer (sp) in the wire. I found that alcohol will easily remove it.

[drussell]

Originally Posted by rca2000

But my 29JC20 does NOT have a good tube, the red gun is weak--and will not come up. I wonder why--maybe my set got a lot more use--or the tube was defective from the beginning. It will work--but is obviously deficient on the reds.

Hmmm, it is interesting that the red is the one that is shot since, if I'm not mistaken, that should be an 21FBP22 picture tube in that set, isn't it, which would have had one of the newer sulphide-based red phosphors? (Although I suppose anything can go wrong with any tube! )

Once again, I find myself referring to Peter A. Keller's excellent book, "The Cathode Ray Tube: Technology, History and Applications" (1991), pp. 180-1:

The 21CYP22 spawned several improved versions. During the late 1950s and early 1960s the emphasis was on increasing the brightness of the color pictures. The screen efficiency of the 21CYP22 was only about 4 percent of that of a similar size monochrome picture tube due to the shadow mask losses and the low efficiency of the red and blue phosphors, which accounted for two-thirds of the screen area. The red phosphor, zinc phosphate: manganese, was particularly troublesome. Not only was its efficiency poor but the color was more orange than red. The 21FBP22 was introduced in 1961 utilizing an all-sulphide phosphor screen patented by Austin Hardy of RCA.* A 50 percent gain in brightness was achieved. Furthermore, all three electron guns operated at about the same beam current to produce white. Previously, short life of the red gun cathode was a serious problem since it had to be driven harder than the green and blue cathodes for proper color balance. It was very common to encounter early color tubes with only two out of three guns working properly with the red gun almost always being the "sick" one. Improved brazed cathode assemblies also increased stability of color balance and contributed to longer life. An otherwise similar tube, the 21FJP22 by RCA (1961), was the first color tube to use a tempered-glass implosion shield laminated to the faceplate. Separate glass implosion windows were prone to dust accumulation between the tube and window because of the high-voltage charging of the faceplate glass and frequent disassembly and cleaning were required. Multiple reflections of ambient light also was a problem from the separate glass surfaces.

One of the most important developments during the early color years was the so-called rare-earth phosphor screen in 1964. Actually only the red phosphor was a rare-earth material, usually based on yttrium with europium activator. The 21FBP22-A used a yttrium vanadate phosphor originally developed by Sylvania and although it did not produce a quantum leap in screen brightness, it did serve to focus phosphor research on the possibilities of rare-earth emitters which would soon become a permanent solution to the brightness problem.**

* Larach, S. and Hardy, A.E. "Cathode-Ray-Tube Phosphors: Principles and Applications," Proc IEEE, Vol 61, No. 7, pp. 915-926, July 1973.
** Hardy, A.E. "Major Developments in Phosphors and Screen Application Techniques for Cathode-Ray Tubes," RCA Engin, Vol. 25, No. 2, pp. 12-18, August/September 1979.

This book is very interesting and a great resource, well worth the money for any interested enthusiast.
Copies may still be available directly from Mr. Keller at <kellerp4(at)frontier(dot)com> and according to:
http://videokarma.org/showthread.php?t=254771, he may even be (or have been) a member of VK.