A (very short) cataract story

[Kevin Kuehn]

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]

Originally Posted by Kevin Kuehn

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]

So apparently CRT implosion was considered a very low risk in a typical home enviornment.

[Eric H]

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.

[Electronic M]

Originally Posted by Kevin Kuehn

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]

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]

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]

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]

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]

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]

Originally Posted by bgadow

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]

Originally Posted by Tom S

... 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:

He didn't bother to have it repaired...