Questions about CRT Safety Glass

Hi, recently I have been working on a 1968 RCA Color Console TV. And I was getting disgusted having to deal with what's known as a 'cataract' with the original 25XP22 picture tube.

I was intending on removing the front safety glass. Then clean up the mess behind it. And simply reinstall it. As you can see and it's funny in its own way, the procedure I went through to take that off was not the way I was supposed to do it.

That's because I didn't find out until later about using heat or heat lamps to soften the glue behind it. So in desperation, I was just using a mixture of electronic circuit cleaner along with a spray can of WD-40.

And just kept prying off the safety glass in pieces and ended up throwing it away. I took for granted that I was going to be able to buy another safety glass someplace.

And of course I found out that you can't. Also, I've been reading some posts on the internet which concern me about this. My question is a simple one. Is it safe to operate this television without the safety glass on the front of the picture tube?

Would I be running the risk of an explosion hazard in my living room if I did? I've already placed an order for a brand new replacement picture tube which should work (25VAEP22).

One thing I do know is that I'm going to make sure I find out before I start doing anything what the correct way is to do something especially like this.

I wouldn't suggest using a CRT without protection in front - if it goes BOOM!! (implosion, not explosion) it could easily maim or kill someone in the room. The glass seriously flies (I've smashed a LOT of CRT's ) and is extremely sharp.

I don't know why you imagined new safety glass would be available?, as it's an integral part of the tube and presumably was never available to the public?.

Simple answer would be a new cabinet design, with a flat piece of safety glass mounted in front of the CRT - as was done before they started adding safety glass to the CRT itself.

Back in the 60's, I did three years in an all-makes/all-models TV repair shop. Old color TVs with 25 kV acceleration were a source of x-rays. Working from ooooooold memory, in the glass layer you removed there might have been something to absorb/attenuate this radiation.

ak

AnalogKid said:

Back in the 60's, I did three years in an all-makes/all-models TV repair shop. Old color TVs with 25 kV acceleration were a source of x-rays. Working from ooooooold memory, in the glass layer you removed there might have been something to absorb/attenuate this radiation.

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There 'should' be no xrays anyway - the design of the set is for the EHT to be low enough not to generate any xrays, and colour TV's had circuits (actually called xray protection in Japanese service manuals, and over-voltage protection in European ones) specifically to prevent it occurring. If the EHT increased, the set automatically shutdown - it was a well known part of the set, as the circuits tended to give problems - one of the high value resistors used to drift high, and this caused the protection to trigger, even though the EHT wasn't high.

I suspect there's probably lead in the glass anyway though, as it was commonly used in glass.

Ah, but the high voltage protection circuits were added *after* health concerns were raised. For a while in the 60's, the typical "high voltage" (US term for EHT) value increased each model year to increase brightness for better viewing in a daylight-lit room. Then came the x-ray scare stories in the news, then came better high voltage regulation and the shutdown circuits. At least, that's the way I remember the progression.

ak

AnalogKid said:

Ah, but the high voltage protection circuits were added *after* health concerns were raised. For a while in the 60's, the typical "high voltage" (US term for EHT) value increased each model year to increase brightness for better viewing in a daylight-lit room. Then came the x-ray scare stories in the news, then came better high voltage regulation and the shutdown circuits. At least, that's the way I remember the progression.

ak

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Might have been the way over there

The USA certainly seem to have a far slacker view of public safety than other countries.

Well, at the time I was doing this, I already figured I was not going to be able to find new safety glass. Though I was looking at the possibility that perhaps I would have found a spare one for sale a used one someplace on the internet.

And that's what I was thinking about at the time. Plus I had worked on a smaller black and white Motorola TV which has an 18 inch screen. This one has what appears to be safety glass up front. I had no problem doing this one. I only took that one apart to get rid of a little bit of fog inside.

This one was actually easier to work with. Because the safety glass was only held in around the edges. It appeared to be something similar to polybutylene you put on car windows. I got that apart and still managed to put it back together with something similar to that polybutylene.

I thought that's what I was going to be doing when I started working on this RCA TV. Was just trying to clean up a dirty ring around the edge of the picture tube. And being as though I didn't research this on the internet first, I kept wondering why it started to seem like there was more adhesive inside there.

And once I made this clumsy move and actually broke it, I figured the damage was already done. And the best thing I could do after this was just to get rid of it. I'm not too particularly worried since I only paid $1.98 to secure the winning bid on this receiver when nobody wanted it. But it did cost me at least $150 to have it shipped from Texas clear to my house.

I have the receiver at least 21 feet away from my easy chair. And I do have access to a fire extinguisher if I have to run and get it if that was the case. Even though I have been restoring and servicing antique radios and televisions for quite some time, you could very well blame my thoughtlessness on my late father who has been deceased since 2008.

He retired after 32 years of service as a first-class electrical lineman in a local steel mill. He taught me a lot about basic electric. But I do remember him working on things like this around the house. He would literally mess up radios and TVs worse than I did.

And I know what I'm talking about. I've seen him also blow up fluorescent light fixtures because of wrong connections he made working on those things. And I myself don't always have the sharpness I used to have like when I was in my twenties and thirties. I'll be turning 55 in 2 months.


And I've gone through a lot of mental struggles ever since I watched the both of my. And I've gone through a lot of mental struggles every since I had witnessed both of my parents pass away on their Death Beds right in front of me. And at that time I was going through a lot to the point where I thought I was not going to be around anymore and literally wanted to die.

And the relatives who my parents wanted me to be close to no longer wanted anything to do with me which also was another emotional battle. I'm doing much better now these last 3 years ever since I've found my new job working as a transport driver for to nursing homes full-time. the radio and TV projects are a side hobby which I have done in memory of my father.

Even though I am doing great now and everything is fine while I'm on my own living alone, my brother and sisters have never really accepted me over the years. And they got much worse with me after the death of my parents. I was always there black sheep and laughingstock regardless of how the parents used to praise me.

so I suppose they could laugh at me now for breaking up that safety glass at the very least. doesn't really bother me at this point.

Rebuff said:

I have the receiver at least 21 feet away from my easy chair. And I do have access to a fire extinguisher if I have to run and get it if that was the case. Even though I have been restoring and servicing antique radios and televisions for quite some time, you could very well blame my thoughtlessness on my late father who has been deceased since 2008.

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The issue isn't fire, it's implosion - and 21+ feet away isn't far enough away to avoid a potential fatal piece of flying glass.

As kids (1960's) a friend got cut on his leg by a piece of CRT glass, when we were playing at the tip, I can still remember the ends of the cut muscle sticking out of his leg.

And that's even more of a reason why I need to change some paperwork with my real estate lawyer just in case I would get seriously hurt or killed. But I'm not all too worried about it just yet even though I know I should be.

One reason I was wanting to purchase a vacuum tube television like this is because I remember my father had a Zenith built in the 1950s. It had a hand wired chassis, no printed circuit boards like the one I have. He got it used and it had multiple problems.

One major problem that had was the picture tube was gassy. I remember he bought a degassing coil which I used to wave around it when I was 12 years old. But we couldn't get all the gas out. He messed the TV up where the picture was only 4 in on the screen and it was a 19 inch receiver.

He took the picture tube out and set it on the utility room floor left it there a few weeks. Then he dragged it in the garage and wrapped towels around it. Actually started breaking it apart with a sledgehammer. He told me that thing really exploded with flying glass all over the place nearly injuring him.

And then he said when he went to break the front of the picture tube with his sledgehammer, it had this sticky solvent in there. Probably adhesive holding that safety glass in I guess.

I also remember my father had another piece of neat looking flat tinted decorative glass. He said it came from another older TV set from the 1950s. We were using it as the top for a handmaid end table my dad made this or we would set our coffee cups on.

Then one day he decided to take that table apart. And then he tried to actually cut that glass to make it smaller. I saw myself where the glass shattered and broke up in little pieces in the garage.

You could hear the snapping sounds probably radiation in there. A few pieces got on his arms and it was burning him. He got treated and everything but I know that scared him to death.

Rebuff said:

I was intending on removing the front safety glass.

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I cringed as soon as I read that!

Many years ago when I had a holiday job in the local TV shop, it was standard procedure to "neck" the tubes of old TVs which were heading to the dump.
To do this, we would remove the back from the TV, stand to the side of the TV so as to be out of the way of any flying glass, and hit the neck of the tube with something heavy.
Usually this just neatly broke off the neck of the tube, but the inrush of air would blast the phosphor from the screen.
Big old CRTs are not something to mess with.

JimB

Well my TV was unplugged and not in used for at least four weeks. Literally no high voltage was present in there at all. And the best thing I could do while working on this was to support the back of the picture tube on pillows.

You know how I used to dispose of old picture tubes years ago? I'd bring the picture tube out in the backyard and set it next to an ash tree which was pretty tall. I put a ladder up against the tree and brought a cement block with me.

Then I'd walk to the top of the ladder about 10 feet up. Dropped the cinder block on the CRT below. Sounded like gunfire neighborhood dogs barking LOL

Nigel Goodwin said:

The USA certainly seem to have a far slacker view of public safety than other countries.

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Nothing gets past you, sparky.

ak

JimB said:

Many years ago when I had a holiday job in the local TV shop, it was standard procedure to "neck" the tubes of old TVs which were heading to the dump.
To do this, we would remove the back from the TV, stand to the side of the TV so as to be out of the way of any flying glass, and hit the neck of the tube with something heavy.

Click to expand...

All we did was remove the socket from the end of the neck, and snap the little glass nib with a pair of pliers. Hiss, inside of neck turns white, then nothing. On older tubes with the large black plastic plug like an oversized octal socket, the nib was inside the center post.

ak

Even though I've ordered a brand new picture tube, what I wouldn't mind doing is to see if I could find another used picture tube with the same number as the one I was working on.

But maybe somebody wants to throw it away because it's burned out. And what I would probably do is take their bird. Picture tube outside. And try to use the proper heating method how to remove the safety glass off of that faulty picture tube.

And then just transfer that glass to my existing picture tube. I'm going to save my old picture tube just in case I might have an opportunity to do that. It's a long shot though.

Somebody would have to be throwing away the same size picture tube for me to do this.

Rebuff said:

Even though I've ordered a brand new picture tube, what I wouldn't mind doing is to see if I could find another used picture tube with the same number as the one I was working on.

But maybe somebody wants to throw it away because it's burned out. And what I would probably do is take their bird. Picture tube outside. And try to use the proper heating method how to remove the safety glass off of that faulty picture tube.

And then just transfer that glass to my existing picture tube. I'm going to save my old picture tube just in case I might have an opportunity to do that. It's a long shot though.

Somebody would have to be throwing away the same size picture tube for me to do this.

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Mistake there, I was trying to say bad picture tube. But came up bird instead lol.

AnalogKid said:

All we did was remove the socket from the end of the neck, and snap the little glass nib with a pair of pliers. Hiss, inside of neck turns white, then nothing. On older tubes with the large black plastic plug like an oversized octal socket, the nib was inside the center post.

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I suspect there's many different ways to do it - we used to remove the socket like you, and then knock the pip off with a screwdriver handle.

JimB said:

I cringed as soon as I read that!

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I too was absolutely horrified.

On a related note, we had a brand new Sony TV at work, and EHT was leaking out of the side of the tube - pretty nasty.

I could only presume that the support wires for the shadow 'mask' (Trinitrons have vertical wires instead of a plate, and a few horizontal wires to support them) must be mounted between the front glass and the bowl glass, and in this case was too far too one side, so sticking out through the glass join. We simply returned the set to Sony as faulty, no point trying to replace a CRT under warranty as there's too much setting up involved for too little money.

Rebuff said:

One major problem that had was the picture tube was gassy. I remember he bought a degassing coil which I used to wave around it when I was 12 years old. But we couldn't get all the gas out.

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That's nothing whatsoever to do with 'gassy', it's purity errors - if deguassing (de-magnetising) it (NOT degassing) doesn't cure it, then it's incorrectly aligned. There are two operations that affect the purity, firstly the forward/reverse position of the scan coils, and secondly a pair of magnetic rings that rotate around the CRT neck. So your CRT needed setting up properly, a customer certainly doesn't need a deguassing coil - the set deguasses automatically every time you turn it on from stone cold.

In that vein, we had a long standing customer who rented a TV from us, an old GEC model - and who actually I was friends with two of her children - she kept ringing up complaining of a 'funny picture' (that was all the description we could get), every time we went we turned the set on, and it was perfect. Anyway, one day we were heading back to the shop, and had some time to spare, so thought we're call in and see how she was doing (she was always good for a tea or coffee with biscuits ) - so we called unexpectedly.

The moment we walked in we noticed a great big speaker next to the TV - turned the TV on, and the purity was absolutely abysmal. Every time she called us out she cleared everything out of the way, so we could get to the set easily - and the set then deguassed itself when turned on.

AnalogKid said:

Back in the 60's, I did three years in an all-makes/all-models TV repair shop. Old color TVs with 25 kV acceleration were a source of x-rays. Working from ooooooold memory, in the glass layer you removed there might have been something to absorb/attenuate this radiation.

Click to expand...

actually in the USA in 1968, that is correct... TVs came with X-ray warnings, and the front safety glass as well as the front glass of the tube envelope itself were made of leaded glass.
you can put a 1/4" piece of plexiglas in front of the tube to reduce the implosion hazard.
a digital camera reacts to x-rays, but i'm not sure what the threshold is... x-rays show up as white snow/glitches in the picture. if you are in doubt, turning down the overall brightness reduces the beam current, which reduces x-ray emissions