Digging into the CTC-9

[leadlike]

I was surprised that my hands weren't shredded by the incident. It would appear that they shielded my face from harm. I only had two small cuts in the palm of my right hand-the one that wasn't holding the paper towel.

Judging by the spray pattern the glass made-it looks as if most of the force was directed towards one side-luckily out of our direction. The shadow mask was shredded, I was surprised, it was made of pretty thick metal, like the kind you would need metal shears for. That certainly worked in our favor as well. All that is left now is the gun assembly, and the orphaned safety glass-in case anyone needs a roundie safety glass.

I wished that hot knife method had worked. But this type of pva was not heat sensitive AT ALL. We got the wire deadly hot, and just for the heck of it, blowtorched it just below the melting point, and it still did absolutely nothing to the worklight-softened PVA.

Now, I have another 21fj that is cataract-free. I have that installed already, and I had a miserable picture on it. All but the green gun tested as bad. After letting it cook at 8 volts, the other two guns came up, and now I have a crt that tests largely good, with excellent tracking.

But now I had some arcing in the hv cage, and I could only crank up the hv to just under 20kv....

[DaveWM]

well hopefully the let is soak in water method may work...

I will get started on that this weekend.

I am wondering you could just pour some PVA on the glass and set the CRT back on it and then let it cure to replace the PVA after a cateract removal. I assume the safty glass lens is no protection at all with out the PVA.

[DaveWM]

I was thinking of wrapping some packing tape around the perimeter of the lens building a wall then pour in some PVA (white glue I presume) to form a puddle in the middle then puting the CRT in place. Of course the hard part would be to figure out how much glue to pour into the puddle so as to have complete coverage, with out too much over fill causing a huge mess. oh and the last problem would be how to keep the center of the tube from coming into contact with the lens a squeezing out ALL the pva.

perhaps a jig that would support the crt inverted over the lens with just a fraction of an inch separating them during the cure. It sure would be helpfull to know how it was done at the factory.

another option would be to band them if anyone knew how to do that properly.

Stories like this make me worry just a bit about tubes installed with out the safty glass installed.

[leadlike]

It is my understanding that only the later round color crts introduced this method of applying the safety glass. So conceivably, a 21fj without its safety glass wouldn't be any less safe than say, a 21ax. That is why early roundies have the pane of safety glass built into the cabinet.

As for how RCA applied their PVA, I found a small injection nozzle fixture on the side of the crt where it appears the PVA went in. It is basically a glorified plastic washer.

I think if I were to ever attempt this again, I would take my crt to a large controlled oven, such as those used for powder coating, and slowly bring the crt up to temp in that, pull the crt, pop off the safety glass, and then run a cooling cycle to bring it down properly. Simply copying the heating cooling protocols from a crt rebuild operation should be a fine guideline.

[DaveWM]

yea I was not really thinking of roundies when thinking about the banding, I have several caterat rectangle one that have no safty glass in front of them.

so perhaps the factory had a fixture that held them apart and then the pva was just injected in. That does not sound to impossilbe to duplecate.

I can see holding it sideways with the injection port on the bottom and then leaving the top un sealed with tap, fill'r up and then tape off the top side.

[Dave S]

Yikes! It sound like we have all been effectively working back in the pre-OSHA days. I confess to having gone without safety goggles more often than not when handling CRTs. But this thread makes it clear: **it happens. Now I think I'm going to investigate making up a Kevlar suit to go along with the glasses.

[ChrisW6ATV]

Originally Posted by DaveWM

I am wondering you could just pour some PVA on the glass and set the CRT back on it and then let it cure to replace the PVA after a cataract removal. I assume the safety glass lens is no protection at all without the PVA.

I do not know how much protection a now-separate glass lens would provide in case of implosion, but the actual possibility of implosion itself should be no higher from a "naked" 21FJP22 than from the version of that tube sold without the lens and PVA already attached, which is the 21FBP22.