Digging into the CTC-9 - Videokarma.org TV - Video

leadlike · #1 05-19-2010, 08:05 PM

I picked up a '9 Winslow on Craigslist a few months back:

http://www.videokarma.org/showthread.php?t=246304

As found, it had a pretty bad cataract, and produced a sickly green picture that barely held vertical or horizontal sync. After about two minutes of running, I could see a little bit of smoke coming from the HV cage.

I elected to do a full recap. While 90% of the caps in this set are of the modern type (mostly maroon, but some orange drops as well), about a quarter of them tested leaky on my cap checker. I noticed on those that did not test leaky, that when I went to check their values, that the cap checker eye did not open nearly as much as it normally would for a new cap of the same value. For fun, I took some low ohm resistors (5 and 10 ohms) and put them in series with a new cap and tested it-it tested a lot like the older caps. So while this isn't definitive proof, it certainly looks like the older caps had some high ESR.

No issues with the recap. The set powered up, with no smoking. I next decided to tackle the cataract. The picture tube was a 21fj that tested brand new. Playing the tv now, I could see that it produced an excellent picture. I took it to a friend's shop, and we spent all day Saturday working on the thing. First we tried the hot wire method. Heat would not do anything to this stuff. Even stabbing my soldering gun into some of the gunk we had scraped off of the side did very little to it. This was after preheating the tube, etc. Whatever this PVA was, it wasn't going to come off that way.

The safety glass came off perfectly, as outlined on that great series of Youtube posts. Heat guns and work lights saved the day. Well, for a while. After the tube had cooled, I was wiping down the picture tube face with a paper towel before applying the double sided tape when it imploded. That is to say, I had both hands in contact with the face of tube when it seemingly vanished.

When I opened my eyes (I was wearing safety glasses, luckily) my poor friend was hunched over the hood of a car, obviously in pain. I knew I had to have been hurt, but I ran over to him and we began to assess just how badly we were injured. He had taken a large piece of glass straight into the face-it put a nice slice into his chin and under his nose. My worst cut was a piece had sailed past my head, making a neat slice across the middle of my ear, nearly going all of the way through. Needless to say, things could have been much worse. I got cut in about ten places, and holding the bulky shirt I was wearing up to the light, it looks like it has been blasted by rock salt. The sound was tremendous-even though the garage door was down, it was loud enough to bring the neighbors on all four sides of the house over to investigate. I'd wager it was on the sound level of a quarter stick of dynamite going off-it certainly had my ears ringing for the rest of the day.

So that was a bit of a scary setback-there is a LOT more to that cataract removal story-we tried every possible method to pull that thing off without going to the heatgun method, but that would be just too much to write here. After all, there is a tv that needs attention here....

*zenithfan1* · #2 05-19-2010, 09:56 PM

Holy crap! I'm glad no one lost an eye or got killed, that glass could have easily gone into either or both of your necks. WOW! I will be seriously re-thinking using the heat gun method. I think it gets the face too hot while the rest is much cooler in comparison. That is a very bad thing, IMO. These tubes can cook in an oven at the tube re-builder but the whole thing is one even temp then, so the stress of expansion and contraction is even with the whole thing. That's my theory anyway. That's a pretty cabinet on that set BTW. I do believe it's a blonde Anniversary model, the Winslow is kinda french provincial. I have the Anniversary right here next to me in Mahogany, same exact cabinet. The blonde is gorgeous on this model I think. Good luck on getting another CRT, too bad a good one imploded.

We can restore them together as we're about at the same point. I have a lot of work to do on my cabinet though, printed finishes are tricky but I have a plan. Instead of hi-jacking your thread, I'll start my own later

VERY glad you guys lived to tell the tale.

jeyurkon · #3 05-19-2010, 09:57 PM

Ouch!

Thanks for reporting this. I'm sure it'll encourage others to exercise caution.

It's odd that it broke when it did. I assume you were only applying only very light pressure while cleaning up the residue.

John

*zenithfan1* · #4 05-19-2010, 10:02 PM

Maybe it stress fractured and decided to let go when he applied a slight pressure to the face, who knows.

drh4683 · #5 05-19-2010, 11:49 PM

Wow, thank god you guys are OK all things considered and that nobody had serious injuries. This heat gun method seems to have its fair share of dangers and Im starting to advise against it now. I've done some 10+ cataract jobs with success with the heat gun method until I had a 23EGP22 blast into peices in front of my face about 2 years ago, which Im sure most of you remember that disaster. My theory at this point is that the CRT face gets so hot and it starts to expand laterally. The bell of the tube stays cool since its not even heat and it does not expand (like mark pointed out), but when the lens starts to expand, it puts alot of stress at the frit seal and thats probably the weakest link and it fails right there. I could be wrong, I've never conducted stress analysis on a CRT before.

CTC17 had very good luck with the hot wire method on the Zenith tube. The key is keeping enough current going through the wire so that the PVA does not act as a heat sink when you apply the wire, otherwise it stops you dead in your tracks.

As for the sound, I remember exactly what the 23EGP22 sounded like. It was like a bomb, it sent a nice shock wave into the air and it felt like someone punched me in the chest and then there was Phosphor rain for about 30 minutes afterward. It was on a saturday afternoon and my parents were upstairs watching a football game. They both basically screamed out loud wondering what the hell happened and they both ran downstairs to see if I was OK and what happened. The sound was so powerful and intense. Then little phosphor flakes and dust were everywhere and floating in the air and I couldn't believe how far the glass traveled yet amazingly, I was scratch free. I couldn't believe I was OK. The sound of the glass shards striking each other was also incredible. It all happened in microseconds and it was over just like that.

andy · #6 05-19-2010, 11:56 PM

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Phil Nelson · #7 05-20-2010, 12:13 AM

That's terrifying. Thank your lucky stars that neither of you caught a big piece of glass in the jugular.

I just permanently lost all interest in experimenting with cataract removal. If anybody asks me whether it's a good idea, I'll begin by pointing them to this thread.

Phil Nelson

freakaftr8 · #8 05-20-2010, 12:33 AM

Man im glad you guys didn't get it worse than it could have been! I hope you can find another CRT! When I did my Ctc 16 a few years back I was worried about the same thing.

ChrisW6ATV · #9 05-20-2010, 12:45 AM

I am glad to hear you and your friend are (mostly) OK.

AUdubon5425 · #10 05-20-2010, 03:12 AM

So much for the heat gun method - I wouldn't try it at this point.

David Roper · #11 05-20-2010, 03:32 AM

It serves as a reminder that CRTs are *dangerous* lest we get too casual in handling them. That much glass going in every direction at that speed can kill.

leadlike · #12 05-20-2010, 08:01 AM

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 · #13 05-20-2010, 08:53 AM

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 · #14 05-20-2010, 09:09 AM

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 · #15 05-20-2010, 09:23 AM

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.