GE M935AWL roundie part 4 - cataract removal

[@markseymour5558]

Theres a film by rca showing the process of the clear adhesive being applied to the glass, as well as the entire crt being made, interesting stuff

[@69Dartman]

It turned out looking nice but Shango was explaining that you should seal the edge up so dust and dirt doesn't get under the glass with enough time like others are saying here. Be fun to see it running in it's full glory soon.

[@bandersentv]

I'm planning on wrapping it with tape like it had originally.

[@69Dartman]

@@bandersentv I spose if it's really good and sticky that should work quite a while and be way easier to deal with. They make some really good stuff these days.

[@billharris6886]

Congratulations Bob, I have never pulled a bonded faceplate before but, have great respect for the destructive power of an implosion. Being it is a round CRT, there are less stress points than with a rectangular CRT, and therefore, a bit safer. On those 21" color round CRTs, the actual face glass thickness is about a half inch. Back in the 1970's when replacing the 21" round CRTs, we would remove the eight 5/16" mounting screws, pull the CRT from the cabinet, place the CRT face down, then remove the band with the brackets. When reinstalling, the anode goes on the right at the 3 o'clock position and the band tightening screw at the 9 o'clock position. It seems like we first mounted the 4 corner brackets back to the front panel frame very loosely with the band screw removed. Then carefully lowered the CRT back into place and found the place where the CRT wanted to settle into the front panel frame. Then slowly and carefully tightened the corner brackets and tightened the band last.

[@bandersentv]

Thanks for the advice. I really wasn't concerned about the CRT imploding. As you say, the glass is very think. I was worried about cracking the thin face glass. Especially after discovering a chip on the edge.

[@televisionforever]

Looks like you even wore the Shango camo pants for the cataract removal! Very nicely done. I haven't had to do this yet but your series will definitely come in handy as always.

[@bandersentv]

LOL, I was hoping someone would catch that. I'll be doing another soon and may try leaving all the stuff on the CRT neck to make life a bit easier.

[@dbridger620]

Great video Bob, and I'm looking forward to the next one! It never occurred to me that the PVC sheet added a layer of safety to guard against implosion protection, then when you do the cataract repair, the installed tube is not as safe as before. I heard Shango talking about this very subject. With the safety glass in place, there still has to be some measure of protection, I believe.

[@bandersentv]

I've been told it's made from tempered glass so, yes, it should absorb some of the implosion and break up into safe little pieces.

[@davewm9589]

Hi Bob, on the ones i have done I just used single sided adhesive foam tape around the edges. I think I did a complete circle, or may have just been 4 pieces spaced equal around the edges. Then used packing tape to seal out dust. Only thing you need to watch out for is on the sides need to make sure nothing will show past the mask. top and bottom are clearly not a big deal due to the amount of masking there.

[@laurdy]

The retainer ring at 1:26 is actually for purity adjustment. If i'm not mistaken the adhesive glue is actually water soluble.

[@notimetolooz9655]

PVA, polyvinyl acetate, is a main ingredient of "white glue". When it cures it becomes water resistant (not water proof however). I think some people did try soaking the front of color tubes in hot water. It took a very long time to work, so the method just using heat was faster. The glue used on Zenith type tubes is somewhat different and doesn't work using just heat. On Zenith type tubes forcing a wire through the glue works best.

[@f.k.burnham8491]

Bob- You can use Dollar Tree pool noodles split down the center to pad the can. (Also works great on 5 gallon buckets.)

[@force311999]

Or pipe insulation ,is already split

[@suzakule]

Like with most CRTs of this era, the cork that was put in the metal band on mine was hard as a rock, on my GE, and had to be replaced, and obviously there is an UP/ Down orientation, with blue gun on top. If i remember, there is a glass nub demoting top.

[@bandersentv]

Yep, there is a glass nub. The are also the mask registration symbols on the face. I shouldn't have said orientation doesn't matter.

[@TechneMoira]

Job well-done Bob :) Frankly, I've never worked on a CRT that large. I can imagine there's quite a lot of (potential) energy stored in such a huge vacuum bulb... an implosion of this one would generate a lot of explosive energy if it ruptured. This is not a job for the fainthearted ... well done !

[@greggsvintageworkshop8974]

Very nice job getting that off Bob!

[@draggonhedd]

They do make optically clear epoxy for adhering the front panels to LCD monitors, so if you did want to reattach it, you could, and the process is pretty straightforward. I'd put the lens face down, supported by a ring of cardboard or towels, fill it with the clear epoxy, and set the tube on top and let the weight of the tube squeeze the two together. the shape should prevent air bubbles and the epoxy is kind of made to expel those naturally. However, I'm with you in that it's really not necessary.

[@tarstarkusz]

Nice job, Bob. BUT, you should probably put the silicone around the edge. Dust is going to get in there otherwise.

[@bandersentv]

That's why I don't want to use silicone - so I can clean it if needed. Just blow some compressed air through the gap. I'm wary of sealing it and trapping some contamination inside.

[@suzakule]

@@bandersentv I have done 4 so far with Silicone, and " you know who" has done countless amounts, and so far, if you get them VERY clean when you seal them, it should not be a problem

[@bandersentv]

Won't wrapping tape around the perimeter accomplish the same thing?

[@tarstarkusz]

@@bandersentv That's a good idea. It probably will.

[@suzakule]

@@bandersentv For a time yes, but any tape won't stand up to time, it depends on if you want a permanent fix, IF you are ULTRA careful and Clean, putting a few bits of double stick tape and then silicon will last another 30-40 years, and you wont ever have to deal with it again, this is the method that shango has done many times

[@kadyszrybak6280]

The retaining ring is purity adjustment magnet

[@bandersentv]

AH, I was thinking those tabbed rings were for centering but I guess that's not possible with a color CRT

[@Suddenlyits1960]

@bandersentv,That came out nicely and went smoothly. Its going to be interesting to see you reinstall the lense to factory specs. I don't believe I've ever seen anyone do it that way and cover the entire front of the crt with the bonding agent as the factory did. I look forward to that video. What type of adhesive do you plan on using for the best optical clarity? I think you made a good choice doing it indoors too,for the reason your specified,better control of the environment. We've been having some windy days out here and the last thing you want is to reinstall the glass lense and get dirt and dust under the glass.

[@bandersentv]

Oh I'm not doing that. Just going to secure with double sided tape and possibly silicone around the edges

[@notimetolooz9655]

From what I've seen on rectangular color CRTs the adhesive (PVA, polyvinyl acetate) may have been pumped in between the safety glass and the CRT from the bottom. A vacuum pump may have aided this. There is a port at the top and bottom of the edge of the screen. PVA is one of the ingredients of "white glue".

[@Suddenlyits1960]

​@bandersentv My mistake! I misunderstood what you meant. I'd hate to get dust trapped permanently under the lense too. Let us know what tape you decide on.

[@1011010100011]

@@notimetolooz9655 Close... The plastic material was likely polyvinyl butyral (PVB), same as used for laminated auto and architectural safety glass and one of the oldest plastics. In the usual auto/architectural glass fab process the plastic comes in sheets and is milky until baked under a vacuum and/or in an autoclave (with the glass/PVB/glass assembly still under vacuum) with added atmospheric pressure. It would be tough to do this in a DIY setting but I suppose not impossible with one of the films designed for vacuum-press only using a big silicone vacuum bag, and a lot of heat lamps.

[@bobweiss8682]

Your tape/spacers need to be thick enough that the 2 glass panels are NOT in contact with each other at the center of the screen. There needs to be an air gap over the entire viewable area. You should definitely run a bead of RTV sealant all around the edge to keep dirt out. The high voltage static charge will suck dust right in, where you can't wipe it off....

[@bandersentv]

Yep. I'm using the same foam tape as Doug (drh4863) in his tutorial series. It's about 1/8" thick. I was figuring the tape I'll be wrapping the edge with will keep out dust.

[@zundfolge1432]

shango066 glued his safety glass back on and I believe he just went around the edge with some kind of caulking

[@bandersentv]

Yes, he did

[@mikefinn2101]

Bob real nice job Shango has done that. No risk with no safety glass in reality done to keep objects from damaging if thrown at the CRT like kids playing around but I sure no one will that.

[@bandersentv]

Oh no. It's there to protect from CRT implosion ejecting glass. Nothing to do with anyone throwing things at it. The biggest risk is the CRT envelope failing on the backside glass shooting out the front

[@force311999]

He is still putting the glass back on he ment it may not protect as well with out being laminated to the tube I remember when windshields would get like that also

[@bandersentv]

@@force311999 It doesn't really protect at all without being laminated. Probably makes it more dangerous than not having anything as it's much thinner than the CRT glass and breaks easily.

[@force311999]

If i was doing these today i would build some kind of hoist to lift it out of the cab. And then flip it over in air i donot have the sranth to lift that anymore

[@chetpomeroy1399]

I see Bob doesn't deck himself out with protective attire like Shango does. As I remember, Doug Harland didn't either.

[@bandersentv]

Handled 100s of CRTs over 4 decades. I gave a healthy respect for them and understand the risks.

[@Suddenlyits1960]

The tv repairman didn't back inl the day either when they swapped out a tube. As long as the person doing the work is careful there's little risk of implosion.

[@tomcarlson3913]

The 21FBP22 and 21GUP22 are the ones that don't get cataracts. Those tubes don't glue the safety glass on, but instead have a rubber spacer/gasket around the perimeter and are held on to the face by those fingers on the mounting band. The safety glass and CRT envelope on the glued 21FJP22 is no different than the glass on the 21FBP22 so really in doing a cataract removal and safety glass perimeter reattachment what you're doing is converting a 21FJP into a 21FBP.

[@bandersentv]

Huh. I'm surprised it's not laminated safety glass. How is it supposed to protect you from implosion?

[@tomcarlson3913]

@@bandersentv Laminated safety glass was only available as a flat sheet back then IIRC. Monochrome sets were starting to move away from laminated and over to tempered by the second half of the 50's (I've owned a few sets of that era with flat single layer tempered safety glass). I think the general idea was that it was fine if the CRT shattered the safety glass as long as the safety glass contained the initial implosion energy and either deflected projectiles back or robbed them of momentum so they would drop 1-3" away from the TV. There's film of color CRT implosion safety tests out there. You'd have to talk with a CRT design engineer who was alive then to get the exact reasoning. I'm just telling you what I've seen as someone who currently owns 25 roundy color TVs (and has had 10-15 more).

[@SeekingTheLoveThatGodMeans7648]

Didn't some of these roundies come with a separate front safety glass anyhow? That was what the servicer on my family's old roundie did the last time he replaced a picture tube. I believe it was a 21CYP22. If the main tube imploded, then maybe the safety glass could lose its mounting security and break too, without that original adhesive. But I haven't heard yet of any de-cataracted tube, with safety glass replaced with an air gap, imploding and scattering glass out the front. I suppose an arrangement like this could be put to a sacrificial test, using a de-cataracted dud tube still under vacuum and breaking it from behind, to see if the safety glass would hold. With most of the beefiness of the funnel being around the rim, I'd think it probably would. The 21CYP22 tube took a separate front safety glass per the tube manual.

[@bandersentv]

Yes, but they used actually laminated safety glass like all the B&W sets do. This lens is just plain glass and breaks easily. It would not survive an imploding CRT. You probably haven't heard about it happening, because it's very rare for a CRT to implode.

[@jospence9556]

That was a RCA made tube. GEs first color CRT was the portacolor in 1965. They did make a lot of B/W ones before

[@bandersentv]

Thanks. That's what I figured. Curious that it has a GE label and nothing about RCA. I have one of those early portacolor sets. Truly awful resolution 😝

[@jospence9556]

The glass in front does give some protection. Also, if you don't seal the edge with dark silicone, you will see the gap from the front bezel.

[@jospence9556]

RCA probably shipped plain tube's no labels to GE since they were buying them in bulk, and GE added their labels

[@bandersentv]

​@@jospence9556 Not if it isn't fully bonded. It's actually more dangerous as it isn't safety glass. If the CRT implodes it will also shatter and send even more glass flying.

[@69Dartman]

The Porta Color sets were just about the cheapest small color sets you could buy. I remember as a kid seeing new ones selling for 188 bucks which was uber cheap back then. They had a really weird in line setup with huge color stripes so like you said horrible resolution even for SD. I had one I got going too for a while. I liked that it was small and pretty bright and colorful but the resolution was truly awful. It was hard to read fine print on screen with it if you were too close. BUT they were uber cheap. I don't have it anymore so just going from memory, and I think they kept using a hybrid tube transistor chassis long after everyone else was fully solid state.

[@zinckensteel]

I wonder if you could replicate the original glue layer by turning things upside down and using an optically clear epoxy. Maybe even put the whole assembly on a turn table spinning fast enough to sling the epoxy up the sides of the glass smoothly. Think of a vertical glass lathe without a torch; the crt would have to spin in sync with the safety glass while it was lowered onto the bubble-free uncured epoxy. Using the same stuff for bar tops it's not too hard to avoid bubbles if you use a thin first layer, let it cure, then add the main volume of resin, spin it up slowly and then hit it gently with a torch - the heat pops any surface bubbles and liquifies the mix to allow deeper bubbles to rise. It also speeds up the curing process, but that won't matter if the cure time is a few hours typically.

[@bandersentv]

Maybe with some type of RTV/silicon but I'd be wary of using something as rigid as epoxy. CRTs do get warm in use and the glass goes expand a bit.

[@garystrait3289]

Also, if you epoxy it, there's no chance for a do-over if you end up getting bubbles, and since the CRT and lens aren't flat, I think it would be hard to get the epoxy even enough to avoid bubbles.

[@garystrait3289]

I notice your initial advice was to avoid holding the heat gun in one spot, but once the adhesive starting coming loose, you did pretty much that. You might have been OK, but I'd hate to see you fracture that lens. Maybe better to let the heat lamp keep working a bit longer. I've enjoyed your videos, and learned a lot from them. My parents had an RCA color roundie, CTC-16, and remember a serviceman coming to work on it several times. I also remember doing some service myself later on, after getting some expertise on other things (building a solid state Heathkit color TV, and getting a degree in electrical engineering), but still didn't have as much practical knowledge as you have (the engineering degree is good for theory, but not as much about practical knowledge on failure modes, etc.). Sadly, my parents got rid of their old roundie years ago. I'd enjoy the challenge of restoring it today if it were still here. It was a good TV for years. I even remember watching the Apollo moon landing on it. I did just restore (mostly) the Heathkit TV I built in 1972. It's good now, except the picture is a bit snowy, even with a converter box input. I suspect the IF, and maybe tuner, could use some restoration and realignment, but I don't have enough test equipment for that. I see plenty on eBay, I may get something just to try this, at least the IF. I'd still be hesitant to mess with the tuner, since moving anything can change inductances and capacitances and affect the alignment (Heathkit provided those parts pre-built and pre-aligned, so the kitbuilder wouldn't have to touch them, but they did provide full instrument alignment instructions in the manual, just in case you needed them). Building (and restoring) the Heathkit gave me a good education on aligning the color. It's not really that hard, though don't expect perfection. (On your sets, you should be able to unbolt the convergence board and its mounting bracket, flip it bottom to top and back to front, and attach it to 2 mounting screws provided on the cabinet for that, so the board is above the cabinet, facing forward. That's so you can reach to adjust the pots (and coils too) on that board for convergence, while viewing the front of the TV. Maybe your Sams already tells you that, or maybe you already know that. Nice touch for the serviceman by RCA, and looks like GE did it too.

[@bandersentv]

Avoid keeping it in one spot for too long and have it just close enough to get the job done. The heat lamp does not get hot enough to complete the process.

[@force311999]

Brave handeling it with our protecting yourself. I used to have thick wool coat and facesheild etc. Those can explode

[@bandersentv]

Implode, but sure so can any other CRT I've ever worked with. About a dozen lying around just in that room alone.

[@Audion]

I would not trust that trash can to not collapse further than I could throw the trash can. I would think that outside strapping would be required to reinforce it maintaining a round shape. Also, I would have filled it with packing peanuts or other padding in the event it does collapse or split.

[@bandersentv]

Huh? There is no outside strapping. That was the CRT mounting band. It is a very sturdy can - more than adequate for the task. CRT is not that heavy

[@PerspectiveEngineer]

Ok..... 😂👍

[@bandersentv]

Ok what?

[@Retep4565]

I noticed you didn't use any protection. My late father taught me to always wear a condom for protection, though he wasn't a tv repairman so I'm not sure how valuable that advice is. Shango66 had one implode on him in one of his videos.

[@bandersentv]

I've been working with CRTs for decades without protection. Been doing it for 15 years on KZbin. Not sure why everyone is concerned now.

[@notimetolooz9655]

@@bandersentv The only thing is that sounds like "famous last words".

[@bandersentv]

@@notimetolooz9655 I just find it amusing that in all my previous videos I'm surrounded by bare CRTs and no one said anything. Even in this room there are half a dozen other CRTs lying round including two with metal cones.

[@notimetolooz9655]

@@bandersentv I think it could be because you didn't heat the other tubes up with a hot air gun to 200 degrees or whatever. Also these color tubes are large and heavy to handle.

[@hotpuppy1]

Why take the stuff off the tube neck? It won't be in the way. You won't be grabbing it by the neck anyway.

[@bandersentv]

So nothing gets damaged. Don't want that convergence board flopping around and putting stress on the fragile coils.

[@johnsenchak]

DUDE inside your house ?

[@bandersentv]

Sure, why not?

[@69Dartman]

@@johnsenchak It's his house and looks like the spare room to put the nicer sets in and work on them. I worked in the garage most of the time when I was a kid at home but I have my house now so I work on projects in the computer room and the living room. As long as the significant other is ok with it he's golden. Also winters suck working in the garage or basement.

[@Suddenlyits1960]

I don't see anyrhing wrong wirh doing this inside the garage or house. The risk of implosion is extremely remote as long as the tube is handled with care and nothing happens to the backside. Tv repairman used to swap out crts all the time in the customers home. Plus when he goes to rebond the lense he doesn't have to worry as much about dust or debris blowing around and getting behind the lense.

[@notimetolooz9655]

@@Suddenlyits1960 Except getting glass fragments out of carpet isn't easy! 😐

[@flukep1228]

Should have on a thick long sleeve shirt and a safety shield for your face. If something happens to the tube and it implodes you want to keep yourself safe. And should seal it all around the tube so no dust can't get in.

[@bandersentv]

Nah, I'm fine