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Servicing the 21FBP22
My 63 zenith 26KC20 still has its original 21FBP22 with the typical olive green screen. I got the set from the original owners and they kept it in their clean attic since the 1970s.
When I got the set this summer, I was surprised to see that a 21FBP22 had a "decayed" or "catarac" look to it around the perimeter. It looked almost as if vasaline had been smeared around the lens from the inside. Just yesterday, I decided to take apart my first 21FBP22 to see what I could do about cleaning it up. Like any crt project, it is very careful work and one wrong move is a disaster! After the chassis removal etc the tube basically simple to remove. However, it came out with metal framework around it. This frame mounted the tv to the cabinet and also held the lens against the crt. The crt had to be lifted out of the frame rather than just pulling it off the crt. I did this by supporting the 4 corners of the crt frame with 4 beta tapes to keep the face of the lens from contacting the surface of the workbench. The crt basically lifted out with the lens still attached. The lens is actually not bonded at all to the crt. Its actually a rubber gasket that fits around the lens and just presses against the crt and is held in place when the crt mounting hardware is reinstalled. What I found was that the rubber gasket used a grease type material that was used to help make installation of the gasket easy. I pulled off the gasket. They are a very high quality rubber that flexes nicely, it does not age (dry rot etc) This greasy substance caused the haze to develop between the lens and the crt. im thinking this is because it was in an attic, which probably got pretty hot in the summer and just baked up there. Ive never seen this with any other 21FBP22 of its type. The gasket cleaned nicely, did not leave a sticky residue after cleaning and fit back on the lens. After cleaning the crt and lens with windex and reinstalling, the set looks new. Threw out this experience, I also found out that the 21FBP22 actually has green phosphor, as the screen is green with the lens removed. Now you can see the before and after pictures. The point- Working on a 21FBP22 is way easyer than a 21FJP22!!! No heat gun, no special tools. Just be careful not to drop it!! I was nervous the entire time, as Ive experienced crt lens breakage. It took about 1.5 hours from start to finish. In the first "before" picture, notice the dark tinge around the perimeter of the lens. Thats the evaporated gasket grease.
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I tolerate the present by living in the past... To see drh4683's photo page, click here To see drh4683's youtube page, click here Last edited by drh4683; 10-23-2003 at 08:55 PM. |
#2
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the completed project
Now the crt looks as good as any other 21FBP22. the set is much more pleasing too look at as it is to watch now! Before the haze defocused the immage, now the picture is clear and sharp!
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#3
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Doug,
I've got an RCA CTC-16A with exactly the same grease film problem on a 21FBP22. Some day I'll get it cleaned. The whole chassis has to come out to remove the CRT so it is a pain in the ass job that is easy to put off. I do not feel comfortable handling large 70 degree CRT's like these either. The imploding glass can do a lot of damage to the person carrying the tube if it goes thump. You really should wear eye protection or better a full face shield, a leather welder's apron or coat and gauntlet gloves IMO. One tube that really frightens me is the 27 inch B&W in my 1953 Admiral. BTW, did you happen to take a picture of the naked front of the Zenith CRT without the safety plate that you could post? You said it was green? Last edited by Rob; 10-23-2003 at 09:25 PM. |
#4
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Doug,
The original 21FBP22 in my Curtis Mathes had the same set up with the rubber gasket. I, too, was surprised that the gasket had not deteriorated in any way. There was a little bit of oily film on the inside of the safety glass, but not too bad. Could tell this set had probably stayed in the house. So far, I've yanked a few FBP's and this one was the only one using the high-grade gasket.
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Charlie Trahan He who dies with the most toys still dies. |
#5
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Yes, the crt phosphor is actually an olive green. Believe me, I would have loved to take pictures of this process, but it would have been a jinx as something would have happened and then I had pictures to show how it was............no, basically, I was too anxious to finish the job and didnt get any pics.
If you take the crt apart, the grease all collects at the bottom of the crt, like a big slime pocket between the outside of the lens and the frame piece. Gravity pulled it all down with extreme heat from being in an attic. I cant see how this just happens under normal conditions. |
Audiokarma |
#6
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Quote:
Some extreme case such as a tube being dropped and the faceplate or rim striking a hard surface such as a concrete floor would obviously result in an implosion, but proper care in handling the tube is typically adequate to prevent such extreme accidents. Certainly, adequate protective clothing should be worn "just in case" of a disaster, even though such disasters are unlikely. "Fear" of handling such tubes can actually be almost as harmful as careless handling, since one's coordination and judgement may be significantly impaired by fear. A healthy respect for the hazards inherent in handling a large tube is essential, but attempting to service such a tube while under the influence of fear can be as dangerous as attempting to do so while under the influence of alcohol, fatigue, certain medications, or other substances. Last edited by jshorva65; 07-21-2009 at 01:57 AM. |
#7
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Quote:
The chances of an electrolytic cap exploding and putting an eye out are probably a lot better than having a tube implode and slice you up, but neither sounds like much fun. Charles
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Collecting & restoring TVs in Los Angeles since age 10 |
#8
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21" round tubes are very rugged and forgiving. Not to say you can't break them, you must use common sense but they are very tough in their cabinets.of
The trick here is not to remove all of the support ears with the tube as they will have to be aligned again and you cannot do this out of the bezel. You loosen all of the ears, undo the large "hose clamp" strap and remove it then you can remove the tube. You will save yourself considerable time by not removing the ears, just loosen them.
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julian Last edited by julianburke; 07-25-2009 at 08:30 PM. |
#9
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Some place I have a Beta video I made of a skinny teenage nerd kid (me), lining up a bunch of CRTs, including a 21FB and several 21FJs, and a Magnavox 27" B&W one, and throwing an anvil at the sides of them to see how big a kaboom they'd make. If I can find it, I'll post it on the condition I won't get booted out of AK
Looking back regretfully today, they were all good tubes. I just kept getting so many of them, and they were worthless (as were the TVs they belonged to). Also at that time (1980-ish), a 21" round color tube was $39, and any B&W tube (except electrostatic) was $16.95 out the door from any rebuilder. So therewith I plead not guilty. I also used to put roundie color sets out for the trash man, and help him heave them into the crusher. I'd put a gentlemens' bet on how many seconds until the KABOOM would be heard inside the truck. Those were the days... Charles
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Collecting & restoring TVs in Los Angeles since age 10 |
#10
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Quote:
During my late teens, while working at a local repair shop, I was also involved in the destruction of some tubes which would be considered "rebuildable duds" today. All were confirmed too weak to produce a decent picture, and most of them were "early rectangular" color tubes of the 25AP22 to 25V... era. Today, I'm sure most or all of us can agree that the only acceptable reason for destruction of a "collectible" tube would be a dud tube which also had a pre-existing severe case of phosphor "burn-in" damage which would render the tube beyond restoration through re-gunning. A tube with good emission but having phosphor damage, however, might be useful as a "test" tube, perhaps installed in a cabinet which, although structurally sound, had a faux-finish in unrecoverable condition. Last edited by jshorva65; 07-23-2009 at 07:07 AM. |
Audiokarma |
#11
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Quote:
When I worked for the local TV shop mentioned earlier, it was standard procedure to save any Good used tubes (there was a storage room upstairs having a wall of cushioned shelves for their storage) and we were required to neck all duds before putting them to the curb. As it was explained to me, the force of the implosion had been known to result in the driver's losing control of the truck in the event that a tube should implode while the truck was in motion, potentially resulting in a serious accident. Glass shards ejected from the rear or top of the truck could also have shredded tires on passing vehicles, potentially causing drivers to lose control of their cars as a result of tire blowouts. Even in an area where Safe Disposal was not formally required by law, the possibility of a costly lawsuit for such negligence served as an effective deterrent for most professional TV Service facilities. Some time before my first job at a TV shop, I accompanied some older cousins (ages from about 15 to 21) on a "target practice" trip into a clearing in a wooded area on my grandparents' property that was used as a dumping ground for junk and a target range. I was about 10 years old at the time. Several junked B/W sets, 60s models as I remember, of various sizes and several empty beer bottles were arranged as targets and shot with rifles and shotguns. The object was to hit the rims of the tubes to weaken the glass, thus causing implosions. Target range was 50 yards. As the youngest person out there, I was allowed to fire ONE shot from a 30.06 with a scope. Being a REALLY crummy marksman, it hit the mask instead of the tube rim. About five sets were shot that day, resulting in LOUD implosions with all except one. Last edited by jshorva65; 07-23-2009 at 07:40 PM. |
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