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Bubbled/delaminated screens

falter

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Jan 22, 2011
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I've been looking for a while now for a VR201 to go with my DEC Rainbow. However, every one I've seen for sale seems to have that awful bubbling inside the glass. Like... every one! Don't know if this is a DEC thing or what... but I'm wondering.. is it anything to worry about? I've seen pics of monitors with spots working. Just not super appealing visually.
 
There's been plenty written on this and multiple YoutTube videos. Basically, the PVA-attached safety shield is delaminating. If you search for "CRT Cataract" you'll come up with a bunch of hits. Here's a non-YT example and here's a YT example, for the reading-impaired

Bottom line is that, using heat and care, you remove the plastic/glass shield from the CRT face and clean things up. If/how you re-attach it is a matter of opinion.
 
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There's been plenty written on this and multiple YoutTube videos. Basically, the PVA-attached safety shield is delaminating. If you search for "CRT Cataract" you'll come up with a bunch of hits. Here's a non-YT example and here's a YT example, for the reading-impaired

Bottom line is that, using heat and care, you remove the plastic/glass shield from the CRT face and clean things up. If/how you re-attach it is a matter of opinion.

Ok thanks... I didn't quite know the term. It's still a big deal to me - just because I'm too nervous working with CRTs and the voltages involved to really mess around with them. But I'm guessing as i've seen 20 of these VR201s with the cataracts happening that it's pretty much something I'm gonna have to live with or get over my fear of to fix.
 
And if a guy who enjoys destroying them can successfully repair them...

This is one of those few chores in life I wouldn't tackle. I'd be too nervous about breaking the tube to work steadily. I've seen what tubes with that extra safety removed do when they break and I have no desire to be around one with a torch.
 
Torch? The ones I posted use a hot air gun--and preheat the CRT before starting with that. The goal is to get the thing to around 220-250F to soften the PVA.

I don't know about doing this for plain old 12" B&W CRTs, but there are some oddball bottles that are worth playing with, I think. Think some of the old HP wide-screen terminals, for example.
 
I just watched that video series. I enjoyed it very much, both the glass and the video image looked beautiful after he was done with it! I'd love to try that cataract removal someday.
 
Torch? The ones I posted use a hot air gun--and preheat the CRT before starting with that. The goal is to get the thing to around 220-250F to soften the PVA.

I don't know about doing this for plain old 12" B&W CRTs, but there are some oddball bottles that are worth playing with, I think. Think some of the old HP wide-screen terminals, for example.

I didn't get a chance to watch that yet. The only times I've seen this done or talked to someone who did it, they used a propane torch, which I thought was crazy. I'd say half were successes and the other half disasters.
 
I didn't get a chance to watch that yet. The only times I've seen this done or talked to someone who did it, they used a propane torch, which I thought was crazy. I'd say half were successes and the other half disasters.

I've only done this once, so maybe was just lucky, but I only needed to use an old hair drier to warm the screen, safety lense and what was left of the bonding adhesive. I was then able to prise it apart. In fact some of the adhesive had turned into a sticky goo that had started leaking out onto the motherboard!

There's some pictures of my screen before, during and after in this thread

http://www.vcfed.org/forum/showthre...uilt-LSI-M-THREE-computer-restoration-project
 
I was concerned about this too for a couple of old terminals I have. I have a Hazeltine 1520 terminal that the front protective screen eventually fell off by itself. I do still have to clean that up when I get to it but this one was the worst of my terminals.
 
I have done this on a HP 2640 and a DEC VR201. With the HP just a 5 by 5 centimeter spot in the middle was keeping the glass to the CRT so it could be removed easily without heating. But the VR201 had just bubbles at the edges so some other method has to be used since I didn’t want to heat up the CRT at all.

I researched PVAc and found that it is soluble in various esters. I then bought a bottle of butylacetate and used a syringe for filling inkjet cartridges to inject butylacetate inbetween the glass and the CRT. I sealed everything with some plastic foil for a couple of days and repeated the process. After a week the glass came lose without any force and the remaining glue could be removed easily.

One good thing with butylacetate is that it has quite high boiling temperature. Also it is not harmeful to the health in low concentration. It mostly smell banana or fruity.

And I was wearing face protection and thick clothes when working with it.
 
I've only done this once, so maybe was just lucky, but I only needed to use an old hair drier to warm the screen, safety lense and what was left of the bonding adhesive.
This may be the difference between 12-14" CRTs and the 25" ones the others are doing.

I researched PVAc and found that it is soluble in various esters. I then bought a bottle of butylacetate and used a syringe for filling inkjet cartridges to inject butylacetate inbetween the glass and the CRT.

This sounds like a really good idea.
 
I researched PVAc and found that it is soluble in various esters. I then bought a bottle of butylacetate and used a syringe for filling inkjet cartridges to inject butylacetate inbetween the glass and the CRT.

Somewhere, there is a description of using Butyl Cellosolve to do this. I wish I could find it again.
I bought some, then have been scared to try it because of the toxicity.
 
Somewhere, there is a description of using Butyl Cellosolve to do this. I wish I could find it again.
I bought some, then have been scared to try it because of the toxicity.

I have no idea what Butyl Cellosolve contain but Butyl acetate seems to be quite non toxic compared to many other solvents as long you stay away from drinking it and work in an area with good ventilation.

https://www.nj.gov/health/eoh/rtkweb/documents/fs/1329.pdf
 
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