I have some questions about CRT cataracts. I was wondering if roundies show cataracts more than rectangular type CRT's? Does running the set prevent or stall the onset of a cataract? I recently saw a Shango YouTube that mentions cataracts happen more in a humid environment than a dry climate. Is that true? Which brand has more cataracts, RCA or Zenith? I understand that it's cause is a breakdown of the PVA material used in bonding the safety glass piece to the front of the screen. Can a B/W tv have a cataract? Just curious. Sony brands seem rare to have cataracts, but maybe that's because there not 50 some years old.

RCA and Zenith tubes both have cataracts, they just look different. I repaired a zenith style cataract by slicing the safety glass off with a guitar string, cleaning off all the old PVA, and then reattaching the glass. Not a fun job, but anyone with patience and good personal protective equipment can do it.

If you want a perfect looking 60s set, short of finding a more recently made NOS picture tube, I think cataract repair is unavoidable.

If a B&W tube had the same kind of bonded faceplate, it could get a cataract, but I don't know how common it was to build monochrome tubes that way.

It seems reasonable that humidity would affect the rate of deterioration - after all, soaking in water is one way to soften the PVA for removal; but I don't really know.

I don't think running the tv would affect it much. I suppose if it got really warm it might deteriorate quicker. Perhaps if you left the set in direct sunlight it would hasten it.

I've seen a couple of monochrome sets with cataracts they seem less common with the vulnerable bonded safety glass tubes though. Some of them had wrap-around safety glass that you can't get wire or clothes pins into...I have a hard time imagining a practical method of removal for the average hobbiest.

Zenith cataracts are the better to have IMO... they tend to stay clear and only affect the color (act as a green filter) vs the RCA type that tends to become cloudy and difficult to discern image through. Also you can slice through a Zenith cataract cold with wire VS RCAs that require dangerous heat or prying...I've heard of using water to remove cataracts on RCA CRTs but after 3 months of no noticeable progress I gave up on using that technique.

The most ruined cataracts I've seen were from a damp basement in Indiana... some the glass literally fell off when the tube was lifted... water degrades PVA just not as fast as I would like.

I've heard of using water to remove cataracts on RCA CRTs but after 3 months of no noticeable progress I gave up on using that technique.


Has anyone tried the water method and kept the water heated? From chemistry classes I’ve taken I know heat generally increases rate of reaction. Something like this (http://1500W Immersion Heater, Gesail UL-Listed Bucket Water Heater with Heating Element, Submersible Heater with Thermostat and Auto Shutoff Protection, Perfect for Home Travel and Winter Job - Silver https://www.amazon.com/dp/B07JB235C2/ref=cm_sw_r_cp_api_i_gm.gEbQ7H8T6S) could possibly be used.

Thermal imbalance in CRT glass causes implosion and or cracking....As I have learned first hand.

If I'm going to subject a tube to temperature change that could break it I rather do it on a same day process than a same decade process...

When I did the zenith cataract removal, it was amazing to me how no solvent I tried would even touch the PVA, it was a tedious process to manually remove all that remained from the CRT and safety glass. Are RCA tubes the same way?

When I did the zenith cataract removal, it was amazing to me how no solvent I tried would even touch the PVA, it was a tedious process to manually remove all that remained from the CRT and safety glass. Are RCA tubes the same way?

Goofoff can dissolve thin surface residue from the glass after the bulk has been peeled, but it isn't effective dissolving normal thickness of the PVA....I wish I knew a good chemist to come up with something to bulk dissolve PVA...

What I really don't get is why do some CRTs get the cataracts and others don't. Example, most color roundies do, many rectangular color ones do, some do not, do they just have better sealing/bonding on the safety glass?

For example, when we pulled the CTC-90 out of storage, I fully expected to see some kind of cataract on it, but it's perfect. It has a 25v-something from 1979-1980.

What I really don't get is why do some CRTs get the cataracts and others don't. Example, most color roundies do, many rectangular color ones do, some do not, do they just have better sealing/bonding on the safety glass?

For example, when we pulled the CTC-90 out of storage, I fully expected to see some kind of cataract on it, but it's perfect. It has a 25v-something from 1979-1980.

Around 1970-73 they stopped gluing a safety glass onto/using safety glass on most CRT, and instead used a tension band for implosion protection....on those tubes the bare face of the CRT envelope is what you are looking at when watching....pull the CRT and compare the side of the face to a safety glass tube to see if you are curious.

Some tubes do get cataracts slower than others....there were nearly as many CRT makers and rebuilders as there were brands of TV and there were differences in mix that lead to differences in characteristics of the PVA.

Goofoff can dissolve thin surface residue from the glass after the bulk has been peeled, but it isn't effective dissolving normal thickness of the PVA....I wish I knew a good chemist to come up with something to bulk dissolve PVA...

I tried goo gone, acetone, wood stripper, lacquer thinner, paint thinner, as well as soap and water. The most effective thing was just repeated scrubbing until every last trace was gone. I'm kind of afraid of how toxic an actually effective solvent would be! Good thing is, this isn't exactly a job I have to do often.

The very first bonded tubes were b/w, made by Sylvania. I read a little article on it in a late 50's electronics magazine. As Electronic M said, the used a wraparound faceplate. I think I might still have a NOS Channel Master rebuild in the attic with that design.

For general adhesive removal I like WD-40 but I can't remember if I ever tried it when cleaning up PVA residue. At one time I was given a 55 gallon drum of the stuff! Guess I should have tried soaking a CRT in it.

I tried goo gone, acetone, wood stripper, lacquer thinner, paint thinner, as well as soap and water. The most effective thing was just repeated scrubbing until every last trace was gone. I'm kind of afraid of how toxic an actually effective solvent would be! Good thing is, this isn't exactly a job I have to do often.

Well, there are plenty more solvents to try. I'm just spitballing here, but how about: paint stripper (the good shit, not the 'eco-friendly' garbage), brake fluid, xylol, hydrochloric acid, I would say gasoline, but I doubt that would work... methanol, perhaps?

I'm honestly surprised that acetone didn't work. Then again, I was trying to remove a lot of urethane grout haze the other day, and just about nothing worked. Acetone did best, but evaporated so quickly, you couldn't work with it. Xylol did alright, but a little slow.

Well, there are plenty more solvents to try. I'm just spitballing here, but how about: paint stripper (the good shit, not the 'eco-friendly' garbage), brake fluid, xylol, hydrochloric acid, I would say gasoline, but I doubt that would work... methanol, perhaps?

I'm honestly surprised that acetone didn't work. Then again, I was trying to remove a lot of urethane grout haze the other day, and just about nothing worked. Acetone did best, but evaporated so quickly, you couldn't work with it. Xylol did alright, but a little slow.

Acetone worked best for me too, but like you say, it evaporated very fast. The cataract removal for me was kind of a one-off, I don't see myself doing many in the future simply because there's no place to store multiple old TVs at my house.

I use acetone as well and just rub with a rag or newspaper until the surface clears.
Now mind you I do the heat gun and halogen lamp method which some people don't like but it turns the PVA into jelly.

I have a 1962 Zenith b/w with a cataract. It's an RCA rebuilt crt and looks like a date code of 1971.

Interesting. RCA rebuilt a Zenith tube and got the Zenith cataract.

When the CRT rebuilders rebuilt bonded tubes, did they remove the safety glass first, rebuild the tube and then reattach the safety glass? Or did they just rebuild the tube with the safety glass attached? If the former method, what solvent did they use to remove the PVA?

As I recall the tension band/no safety glass CRTs were small, probably no larger than 19 inch CRTs.

The PVA could not withstand the heat of the rebuilding, so had to be removed.

The question would be, did they rebond the safety glass with PVA? RCA obviously did, but how about the small shops?

When I got my rebuilt 21FBP22 from Scotty, it did not have the safety glass re-applied. Doug Harland helped me salvage the glass from a dud and then tape it on the good tube, as is the usual practice for collectors.

I had a friend who worked for Video Display Corporation back in the 1970s. He told me the tubes were heated up and the safety glass removed and usually discarded. They installed tension safety bands on most of the tubes they rebuilt. You could (and I did) special order a tube with the safety glass re-installed for an extra fee. I don't know what they used to reattach the glass, but one I still have has a cataract just like the RCA ones get.

Very interesting! I didn't know anyone installed tension bands on tubes not designed for them. Must have required some real knowledge of how to do it without breaking the tube in the process.

Never mind not breaking the tube, how did they make sure that the tube was safe without a bonded shield? The original manufacturers of rimband tubes did extensive destructive testing to ensure that when the faceplate was broken no glass was hurled more than a few inches.

We have discussed before that the bonding of the safety glass (it appears) was not done to increase strength, but only to seal out dirt. The safety glass did provide protection, but more as an initial absorber of shock than reinforcing the tube, the same as a non-bonded safety glass.

:worried:Did Channel Master make better versions of 23EGP22's to do cataract surgery on, can I do it safely?

I picked up an Admiral combo a while back and the EG's cataract looks like an RCA's does. Not yellow

I tried goo gone, acetone, wood stripper, lacquer thinner, paint thinner, as well as soap and water. The most effective thing was just repeated scrubbing until every last trace was gone. I'm kind of afraid of how toxic an actually effective solvent would be! Good thing is, this isn't exactly a job I have to do often.


What about toluene, benzine or even good 'ol gasoline?

Toluene and especially benzene are toxic. Don't use benzene unless you really know what you are doing.

I don't know about US usage but in UK and Europe "benzene" is C6H6 cyclic aromatic while "benzine" is more or less a very light fraction of gasoline, largely straight chain alkanes. Much less toxic than benzene.