View Full Version : A (very short) cataract story


Dave S
08-31-2015, 08:55 PM
I've been posting a lot on Facebook lately, and sometimes when a story comes up I forget to share it here too. It's a lot of fun over there, but this is a much more august group! Still, I keep looking for the "like" button here when someone says something interesting. It feels a little like trying to press the brake pedal when you're in the passenger seat of the car!

Anyway: I had prepared myself for a major "character building" exercise after always hearing how difficult and dangerous it could be when performing a "cadillac removal." Though I've been monkeying around with old TVs since the sixties, this was the first time I've tried to remove the safety glass from a roundie color CRT, this one a rarely seen 21GVP22. Bracing myself for a difficult job, wearing my safety glasses and thick clothing, I started to pick away at the deteriorated adhesive between the face of the tube and the safety glass. And then the tube just SLID OFF THE GLASS! It scooted halfway across, settled back in and it was all over in 2 seconds. The face of the tube was totally clean and once I hosed it off, so was the safety glass. The 'tools of the trade' (hair dryer and/or kiddie swimming pool) were not needed on this one.
https://farm6.staticflickr.com/5620/21047017305_5307c4edeb_c.jpg (https://flic.kr/p/y4RsYH)[/url]

https://farm6.staticflickr.com/5670/20414151054_710d4d50ee_c.jpg (https://flic.kr/p/y4RsYH)

https://farm1.staticflickr.com/621/21044411121_a12f689e68_c.jpg (https://flic.kr/p/x6VRTC)[url=https://flic.kr/p/y4C7fv]

Radiotronman
08-31-2015, 09:21 PM
Great job! I used the hot sun and wood shim method and mine popped loose after about s half hour. Mine was on 21fjp22. Definitely wold recommend that over the heat gun method. Let the sun do the work for you and it's safer.

DaveWM
09-01-2015, 07:24 AM
they are all different, just depends on how degraded the bonding agent is. Roundies are prob safer, but I would still not use a heat gun (hair dryer prob not get hot enough anyway). safety gear is still needed, I had a 23v go boom on me, you do not want that to happen.

DavGoodlin
09-01-2015, 08:26 AM
I had a 1968 Westinghouse 19" color that looked horrible, with a 1973 replacement
GE 19EYP22 and the same thing happened!
Nice work!

MIPS
09-01-2015, 11:04 AM
The people who tell me of how they managed to implode their tubes amaze me, then they scatter off and pretty much tell the sensationalized story to other people.

Had a guy with a cataract job on an old computer. Swore that if he did it wrong it would explode and kill everyone in the shop or worse, explode when the machine was on display and put him on the hook for liability at his museum. Once he got it off he didn't believe in the foam pad nonsense to reattach the face guard so he thermal formed a piece of lexan over the tube face, bonded that permanently, THEN attached the old face guard over the lexan.

Username1
09-01-2015, 11:18 AM
Well that would be safer..... I believe those tubes have the plastic between the two
pieces of glass to help keep the glass from flying around if it were to get hit while
in your living room. Like laminated glass in your car windscreen.....

.

Dave S
09-01-2015, 01:20 PM
Hmm, now I'm wondering if reinstalling the safety glass without it being bonded to the face of the CRT makes it less effective?

On the other hand, even with my fairly casual handling I have never managed to implode a picture tube and I don't know anyone who has.

Still, ya gotta wonder how it would behave in a worst-case scenario.

DaveWM
09-01-2015, 02:28 PM
it behaves badly, large chunks of CRT over a 20f radius, at least on the rectangle. I have not witnessed a roundie implode. on and the rectangle let go after a somewhat "difficult" attempt at the removal of the bonded lens.

https://www.youtube.com/watch?v=lRJ0otqgmYs

I am sure the bonding agent is a good idea, but not cheap, a while back I looked in to optically clear PVB (think that is what it was) that cures from exposure to UV, VERY expensive. I would think it has to be a non air dry type of bonding or it could take forever to cure.

a more practical solution would be to steel strap the CRT but, again I have no idea of the details on how to accomplish that. I suppose the roundies are less of an issue on the need for some kind of implosion protection, but that is just a guess.

N2IXK
09-01-2015, 03:15 PM
Hmm, now I'm wondering if reinstalling the safety glass without it being bonded to the face of the CRT makes it less effective?

My understanding is that the front faceplate itself is just a piece of glass, sometimes tinted. The "safety" part comes from being bonded to the tube face with the clear resin, forming the glass/resin/glass sandwich usually referred to as "safety glass".

This bonded faceplate system was one of several methods of integral implosion protection. By removing the bonding resin, you are essentially defeating this protection. The separate faceplate may not be sufficient to contain the damage should the tube behind it implode.

With the litigious society we live in , I would be very wary of performing one of these "cataract removal" procedures on a set that was going to be sold or put on public display.

DaveWM
09-01-2015, 03:43 PM
With the litigious society we live in , I would be very wary of performing one of these "cataract removal" procedures on a set that was going to be sold or put on public display.

Ditto

Dave S
09-02-2015, 08:55 AM
The "safety" part comes from being bonded to the tube face with the clear resin, forming the glass/resin/glass sandwich usually referred to as "safety glass".

That was the same conclusion I came to. I have no expertise in that subject, it was just me sittin' under a tree thinkin', but it sure sounds logical.

A whole new area of research for us in the still-using-them-decades-after-any-sensible-design-engineer-would-have-assumed-they'd-be-gone game!

Findm-Keepm
09-02-2015, 09:57 AM
On the 25AXP22 that imploded on me, the safety plate acted just iike a windshield - broke into a million little pieces, all stuck to to the face of the tube. Mind you, the tube also broke into a million little pieces with a big whoosh, but no high-velocity glass shards. It was if I had broken a large glass jug, but with the whoosh of inrushing air.

Here's my only experience of an imploding tube, in 34 years of being in the TV repair arena:

http://videokarma.org/showpost.php?p=2988680&postcount=18

Username1
09-02-2015, 11:34 AM
Looking at the picture above, and reading about how quickly it came apart, I'm wondering
if a simple temperature cycle of freezing to summer sun would just cause the two
pieces of glass to separate quickly and easily.....?

For example, store the tube in a shed or cold car port for a few months in winter, then
as summer comes around, put it in the sun on a not so hot day, and see what happens....

We have all seen sets on CL - some with really bad separation, and some not..
Maybe storage temps, long term have something to do with the progression
of the cataract.....? And maybe a season of extremes will do a lot of the
separation work for us, and do it safer.... Like we don't have to be near it....

.

DaveWM
09-02-2015, 11:47 AM
I have a rectangle that is currently stored out side in a foam shipping box. I put a hole directly above the junction of the bonding agent with a funnel to direct rain water. Removed the plastic tape and dug out some of the bonding agent to aid in trapping water. Its been a few months, maybe next year I will try and see. oh and I have axle grease on the pins and the anode.

StellarTV
09-02-2015, 01:47 PM
That cateract is almost complete- that bonding agent is nearly 100% deteriorated. There was simply nothing there to keep the face adhered. That was too easy. :)

Kevin Kuehn
09-02-2015, 07:43 PM
So do you guys think the glass that's mounted(unbonded) with a spaced gasket in front of a 21FBP22 is an actual piece of safety glass?

DaveWM
09-02-2015, 10:24 PM
So do you guys think the glass that's mounted(unbonded) with a spaced gasket in front of a 21FBP22 is an actual piece of safety glass?

Nope. I think it protects the CRT from getting scratched and maybe from at least taking a direct hit from some outside force, but no way it would actually do anything if the CRT was to for some reason spontaneously implode. If for some reason it took a hit big enough to break thru the lens (lets call it that for now) and still whack the CRT face with enough force cause an implosion, I would think the lens would just add to the shrapnel of glass.

Kevin Kuehn
09-02-2015, 11:24 PM
So apparently CRT implosion was considered a very low risk in a typical home enviornment.

Eric H
09-03-2015, 01:30 AM
Is the unbonded glass on the FBP thicker than the glass that's used on a bonded tube?

On the early sets that uses a separate piece of glass the glass was thick and tempered, in some cases laminated, very tough stuff.

I have a Setchell Carlson that uses a glass cover, not bonded to the tube, just tped to it around the edges.

I've always felt such a situation would just add to the flying glass if it ever did manage to get broken but I guess the idea is to prevent the CRT from taking a direct hit from flying objects, possibly a Rolling Pin in the event of a family argument.

I remember once when I was a kid I was messing around with an old Transistor Radio, somehow the Ferrite rod in the antenna got broken and went flying, it hit the CRT of our 19" RCA B&W portable (no safety glass) hard enough to put a small nick in it. :eek:

Electronic M
09-03-2015, 01:47 AM
So do you guys think the glass that's mounted(unbonded) with a spaced gasket in front of a 21FBP22 is an actual piece of safety glass?

I always figured that since they made FBPs for several years (longer runs than the AXP or CYP), that they are safe enough for the job of being in a TV set. The lenses I've removed were approximately the same thickness bonded or not on the round screen tubes I've had so I'd assume a de-cated FJP with the glass reattached is probably as good as an FBP safety wise.

Tom S
09-03-2015, 09:17 AM
To tell you the truth I've Never gone to a house because the tube just went up. I have had sets come to the shop with a hole directly in the center of the tube. LOL the guy said he was cleaning his gun. BS it was a Packer game problem.

old_tv_nut
09-03-2015, 11:27 AM
We have had similar discussions before. It is my belief that the safety glass only protects against objects striking the face (whether bonded or air spaced) and does not add to the strength of the tube. The bonding IMO merely prevents dust from collecting between the safety glass and the tube.

Someone mentioned the idea of adding a band to a roundie. It is my opinion that the effect of this is unknown and could actually make the tube weaker in some spots. This is not a place for by-guess engineering. Later tubes with an integral implosion band were designed specifically to be strengthened by the compression (and in fact can be dangerous without it) and not be overly weakened in any areas where the band reduced the compressive force of the atmosphere (which I imagine could occur in some part of the bell).

DaveWM
09-03-2015, 11:30 AM
I mentioned banding but not a roundie (was musing over my exp with an imploded rectangle, so I can see how should have been more specific). Never seen a banded roundie.

I don't know this for a fact but I seem to recall discussions of hawk eye rebuilds that started out as bonded (rectangles again) that when he rebuilt they were banded. It would be great to find out from him directly, I tried but don't recall getting an answer.

old_tv_nut
09-03-2015, 11:37 AM
D'oh - sorry. Let me modify: Adding a real compression band to any tube not designed for it seems risky to me. If it's just a low pressure mounting band, that's different.

bgadow
09-04-2015, 10:46 PM
Put me in the camp that believes bonding is not needed for safety. I suspect that somewhere there must be a standard for safety glass/implosion protection put out by the government? When bonded tubes were new the marketing was about style & sealing out dirt, not protection. I wonder if optics played a part, as well. The cheaper roundies with unbonded contour glass were clear while the more deluxe, bonded tubes were generally frosted. When mounting a frosted faceplate you'll notice how spacing them out too far quickly hurts clarity. I believe the PVA would help this.

jr_tech
09-04-2015, 11:14 PM
Put me in the camp that believes bonding is not needed for safety. I suspect that somewhere there must be a standard for safety glass/implosion protection put out by the government?

I believe that the bonding is needed to improve safety... If you can find a copy of UL 1418, I think that this details the testing procedure in effect at the time these jugs were produced.

jr

wa2ise
09-05-2015, 03:56 PM
... I have had sets come to the shop with a hole directly in the center of the tube. LOL the guy said he was cleaning his gun. BS it was a Packer game problem.

Then there was the set Elvis shot: :D
http://24.media.tumblr.com/tumblr_kxypq3mCWF1qa8ibao1_500.jpg
He didn't bother to have it repaired...