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Old 10-23-2003, 08:48 PM
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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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Last edited by drh4683; 10-23-2003 at 08:55 PM.
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Old 10-23-2003, 08:51 PM
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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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Old 10-23-2003, 09:19 PM
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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.
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Old 10-24-2003, 03:12 PM
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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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Old 10-24-2003, 03:15 PM
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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.
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Old 07-20-2009, 11:12 PM
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Quote:
Originally Posted by Rob View Post
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.
The 70-degree color tubes are among the most sturdy and least likely to implode of the large tubes, based on my observations. Still, great care must be exercised in handling them, just as with any large CRT. My main source of concern when handling such tubes is adequate attention to preventing neck breakage. I typically cushion surfaces such as floors and workbenches and move tubes around as little as possible when cleaning or otherwise servicing them in order to further minimize any risk of damage which might exist. In more than 30 years since servicing my first "roundie" color set, I have yet to hear of a single case of implosion of any all-glass 70-degree color tube, although I have seen several dead "roundie" tubes which had died of broken necks over the years. Most of those were the result of collision of the back of the set with a nearby wall or other piece of furniture. Every "air dud" roundie tube I've encountered had suffered its fatal blow during some sort of household accident while still housed in its cabinet. The one exception to that was the one my father deliberately "necked" to halt my efforts to repair the set when he considered me too young (I was about 12 then) to be capable of repairing the set and accomplishing the task safely. What he didn't realize was that I had already fixed the set and was about to make the temporary "clipped in" fix a professional-looking permanent repair and complete the final "setup" procedures like grayscale and convergence when I discovered the snapped neck. From then on, he became 100% supportive of my efforts to repair subsequent sets. Word-of-mouth advertising of my skills and some printed flyers my parents helped produce helped to recover several times the cost of the damaged tube. Between repairing his co-workers' sets and repairing sets for tenants at the family's rental properties, I eventually reached a point of earning more in 10 hours' work per week than other kids at school were making with 20-hour work weeks flipping burgers.

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.
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Old 07-21-2009, 09:41 AM
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kx250rider kx250rider is offline
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Quote:
Originally Posted by Rob View Post
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.
It can be scary... I've been lucky; never had one totally blow up in my face. But when I did the cataract removal (heat gun method) job, I wore my motocross gear, including helmet, chest protector & Kevlar neck brace. A welding apron would be good as an alternative, but the throat is probably the most important to protect. Other things coming to mind would be a goalie helmet & armor... At least wrap your neck with a piece of heavy canvas, etc.

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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Old 07-21-2009, 06:19 PM
julianburke julianburke is offline
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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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Old 07-22-2009, 10:57 AM
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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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Old 07-23-2009, 06:26 AM
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Quote:
Originally Posted by kx250rider View Post
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
Let me be the first of a jury of your peers to vote you "Not Guilty By Reason Of Temporary Insanity" as most of us were "temporarily insane" from about age 12 to age 21. As a parent of two children and two stepchildren, I've treated four cases of "Teenybrat Syndrome" and three of the four have fully recovered. The fourth is expected to fully recover sometime next year. "Teenybrat Syndrome" has no known cure except to allow it to run its course, and healing occurs naturally. You seem to be fully rehabilitated. The potential monetary gain (which could have bought plenty of parts for restoration of other sets) lost by their destruction is probably punishment enough, anywway.

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.
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Old 07-23-2009, 07:00 PM
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Quote:
Originally Posted by kx250rider View Post
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
In most cities for several decades, Safe Disposal of CRT's has been required by Municipal Ordinance (or State Law) with fines of up to $500 and/or jail time of up to 6 months for violations. Under such laws, putting a TV set or other CRT device out for trash pickup without first releasing the vacuum is at least a Misdemeanor, and can also expose violators to significant Civil Liability should any personal injury or property damage result from a tube implosion or glass shards ejected from the trash pickup vehicle onto the roadway.

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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