CRT cataracts

[Popester]

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.

[maxhifi]

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.

[old_tv_nut]

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.

[MadMan]

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.

[Electronic M]

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.

[SpaceAge]

Originally Posted by Electronic M

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 could possibly be used.

[Electronic M]

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...

[maxhifi]

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?

[Electronic M]

Originally Posted by maxhifi

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...

[Yamamaya42]

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.

[Electronic M]

Originally Posted by Yamamaya42

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.

[maxhifi]

Originally Posted by Electronic M

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.

[bgadow]

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.

[MadMan]

Originally Posted by maxhifi

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.

[maxhifi]

Originally Posted by MadMan

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.