21FBP22A/21FGUP22 Sylvania Rebuilt C.R.T.

[Tubejunke]

My 1964 Zenith has this rebuilt 21FBP22A/21FGUP22 (never heard of the latter number) tube in it and I am first wondering how it compares to the 21FJP22 and what difference there is. The Sam's folder shows a footnote on mine that says, "Use insulating sleeve and mounting wafer." Not sure what that means. Perhaps some insulation provision due to the metal cabinet.

Also I am wondering if it has the bonded faceplate or the type that the tube just sits down on and there is no bond. Reason being, someone in my home was nice enough to put about a 4" long and rather deep scratch right smack in the middle of the viewing area. The tube (if bonded) has absolutely no cataracts and I wonder if I could simply remove the faceplate in the future to eliminate the nasty scratch. I know either type can be removed, but I would rather lift the tube off of a faceplate than go through the trouble of removing the bonded type.

I guess the easy way out is of course to deal with the scratch and move on without and unnecessary tube removal. More safe too for reckless individuals who gouge TV tubes!

[rca2000]

Not sure but I think it is an RE type of tube. The 21GUP22 is an RE--think it may be the one in my silvertone combo.


Have you tested it--with a good tester like a Beltron or Sencore CR-70...to see what the guns look like--or does the set it is in work well enough to produce a nice picture ?

[holmesuser01]

The FBP/GUP tube does not have a faceplate. At the time, I bought faceplates with a gasket around them when using them on a FJP set.

[Tubejunke]

Originally Posted by rca2000

Not sure but I think it is an RE type of tube. Have you tested it--with a good tester like a Beltron or Sencore CR-70...to see what the guns look like--or does the set it is in work well enough to produce a nice picture ?

Initially I tested it on an Accurate Instruments tester which is more of a simple emissions test and everything looked fine although the blue gun was a tiny bit weaker than the other two. But in playing the TV, the picture is absolutely fabulous. I don't know that I have ever seen a better picture.

To holmesuser01: I thought that it may not have a real faceplate and hoped that it was what I remember back in my shameful days of scrapping these sets. I found that some just sat on a concave piece of glass or plexiglass (not sure). Either way, it was a much better design I think than the bonded.

[walterbeers]

Just an idea about the scratch. Carefully apply clear nail polish to the scratch, let it dry completely, and then buff it out. There are also commercial products out there to remove scratches, buffers, jewelers rouge, etc. No promises, but might be worth a try.

[Tubejunke]

Yeah, that might work & I am familliar with some of the commercial products out there. I probably have way bigger fish to fry still yet with this Zenith. That will be one of the last things I do. Thanks a bunch though!

[Tubejunke]

Originally Posted by rca2000

Not sure but I think it is an RE type of tube. The 21GUP22 is an RE

What is the meaning of RE? So far I gather that it may be an RE and they didn't have a faceplate, not bonded at least. There simply must be some reason why Zenith used one of two different tubes of the same size within a single model year or more. It would be interesting to find out what happened....

[rca2000]

"RE" means " rare earth" as in rare earth phospor...

[walterbeers]

I believe rare earth was basically referring to the red phosphor. It was suppose to be a more vivid red as the original phosphor was more of a reddish orange look. Also the RE phosphor required less beam current to excite it, thus the red gun didn't have to run as strong as the blue and green. With the non RE phosphor tubes the red gun seemed to be the one that usually went weak first.

[Tubejunke]

Well, if it is indeed and RE and RE means better color than I am sold on this idea. I have said it before probably, but when this set was working better it could make on of the most vivid color pictures I have seen.

I am dealing with some video issues right now or AGC one or the other, but even with that going on you can see the eye popping color.

[rca2000]

Not EVERYONE likes a rare earth tube. While they tend to be a LOT more vivid and brighter by far--some feel the color is not quite as good in true "gamut" or whatever--than sulfide or pre-sulfide phospor, like used in the 21AXP22 or 15GP22.

I LIKE RE tubes. Pretty much ALL tubes made after 1971 or such are RE, I think.

[bgadow]

There is a member on here who had, and maybe still has, some NOS roundie faceplates.

[miniman82]

The sulphide tubes were the ones where red turned more orange when driven to high beam currents, but it was less objectionable to viewers than a tube with correct NTSC gamut that could only be viewed in a darkened room because it was so dim (like the 15G). The 21AXP22 tubes can provide pretty decent brightness, but you have to have a stout HV power supply for that. That's why sets like the 21-CT-55 and CTC-4 work so well, and the CTC-5 was such poor performers. My CTC-4 produces a picture that can be seen just fine in normal room lighting, where with my 5 you'd have to draw the drapes and dim the lights.

[Electronic M]

My Silvertone has a 21GUP22 and produces one of the nicest color pictures I've seen. The safety glass is the non-bonded type.

[dtvmcdonald]

That is a great color picture on the Silvertone. Looks much like
wideband color. I there a schematic available? If so,
where. (There's no model # attached.)