Scratched CRT

You must apply an effective filter.

I would definitely leave the scratch alone. And the monitor should be retired for other reasons, as well as the above.

However, if I dearly loved the monitor and was feeling especially mizerly, I would have no qualms about using it as long as the front screen or a replacement remains in place. The stress on the CRT is all inward on the face, and so cracks will not tend to propagate from the outside surface in. And if it does give way due to the crack, the implosion byproducts, (some of which can fly outward despite the inward rushing gas), will be contained by the front screen. Now, since I am not you, and I cannot take responsibility if you get hurt by your imploding CRT, I will recommend that you discard the monitor and wear safety goggles at any time you are within 100 feet of that monitor.

Mainly, it protects the user from highly energetic photons that stream out of the deflection yoke, each delivering up to 55 fempto-fempto Joules to whatever unfortunate body molecule happens to be in the way, elevating its temperature by as much as 4 micro-Kelvins.

Better see a doctor if you ever used that monitor before putting that protective shield on it. Or wear your magnetic shoe pads

Gosh, you really sound like a troll. But I'll assume you are not.

AFAIK, the protective glass protects against glare from overhead lights. Some people worry about the magnetic fields which come off of monitors, but the glass won't protect against those.

Don't worry about the scratches unless they distract you.

If you want to get them out, and if they are not too deep, you may be able to polish them out. This will be a lot of work, but considering that you usually have to pay to throw away an old monitor, it may be worthwhile to give it a shot. Try to find out what amateur astronomers use to grind their mirrors. I think it is called miller's rouge or carborundum or something. Or maybe those are two different things.

Another warning: there may be some kind of coating on the outside of the screen (for example, and anti-glare coating). Polishing will remove this coating, and may change the appearance of the screen image in the region where you polish.

Good luck.

--Mac

Ok, thanks to you both. So basically I shouldn´t worry about the scratch. Unless the CRT implodes, but I guess it would take far more than a simple scratch to happen.

Also I read here:

Also when I referred to "protective glass" I meant the external that you buy and put in front of the screen, not the internal thick leaded glass. I´m trying to make it more clear in case you didn´t take it into account.

I´m worrying about this because I´m not going to replace the CRT in the near future, and I give it extensive use like 16 hours a day.

And Mac I don´t now what you meant by troll, I thought I had the whole troll thing clear because I`ve been reading through the group but then I mmight not have it clear.

Thanks for all the help.

I don't think so, but I am not really qualified to answer the question. Logically, I thing that the amount of X-ray protection is mainly a function of the glass thickness, so if the scratch is not very deep, then you don't need to worry about it.

No. The phosphors are on the inside of the glass. As long as the glass is intact, the phosphors should remain on the inside of the glass.

That is what I understood.

You must be a very hard worker. Or maybe just a computer junkie. ;)

The definition of a troll is somewhat controversial. My usual operating definition is someone whose actual goal in posting is mainly to start long fruitless discussions. Usually the troll is disingenuous, but that isn't a prerequisite. For example, if you were to start a new thread in this group and ask this question:

Why do people still do analog electronics when digital circuits are faster and better at everything?

That would be a troll. Often trolling is most effective when it is more subtle. If people realize that you are trolling, then they sometimes ignore the question.

Another way to troll is to post inflammatory off-topic statements, for example about politics. If the off-topic questions are clearly labeled and in a thread by themselves, it isn't really a troll. But if you casually work inflammatory material into otherwise on-topic posts, that is a good way to troll.

You are welcome.

;-)

And if somehow it is realeased, would I realize ? I mean can I see this kind of gas ?

Great, no misunderstanding :)

Computer junkie, definetly.

Alright, now I´ve got the whole troll thing. You thought that I was posting something that would end in a pointless discussion.

And believe me if you asked analog or digital to me, I´d say analog, simply because I´ve a lot to learn about electronics and I think analog is the best way to really understand electronics. Then I can move completely to digital. I mean, it took a lot of years to trascend to digital, and if I didn´t know analog then I would be missing the most interesting part of the story. But I don´t mean to start a discussion :P

Now, one last question. The leaded glass. It is said that lead is poisonous. But for it to affect me I would have to come in contact with it, wouldn´t I ? And how does exactly the lead look like ?

Thanks for the help, again. We could really go on about this thanks and you are welcome thing, but we wouldn´t really end anytime soon. So let´s just basically state I´m grateful and you are happy to help me :)

I don't think the phosphors are in a gas form. I think they are coated as a thin film on the inside of the glass, but I don't really know. I don't think any normal activities would cause the phosphors to come off of the glass. Even if you broke the glass, I don't think there would be any danger from the phosphors. But again, I don't really know.

Yes, that is what I thought might happen.

Heh, heh. This sort of question is not really in my area of knowledge. What I think is that you would have to grind the glass up into a fine powder and eat or drink it to be poisoned by it. Just touching it or being near it shouldn't cause any negative health effects.

Have A Nice Day

--Mac

I'm not sure what the deal is with your protective glass, but I have sucessfully removed some pretty deep scratches (back in the day when new 19" Sony's were about $1800 and used ones fetched $500 pretty easily) by starting with very fine grit sandpaper and then buffing with rouge. I forget what grits I used, I do have some 1000 grit kicking around the shop still but I think I used 1400 or even finer. The finer the better for the final passes, the grit you have to start with is of course dependent on the depth of the scratch. Make sure you get all the previous grit off without smearing it all over before moving on to the next finer grit of course.

For the final rouge step, as I recall I used a 3/8" bolt about 6 inches long with a bunch of washers and nuts to shore up a 6-8" buffing wheel designed for the buffing equivalent of a grinding pedestal at the end of the bolt, and chucked it in my electric drill. I think I bought the rouge in a four-pack of waxy multi colored sticks, I think it was Dremel but I think Sears carries something similar. Red stick is the rouge. Even on the cheap you're looking at $10-$20, though you can clean up dozens of monitors once you're set up. You'll ruin your drill eventually becuase they're not set up for high lateral loads. Oh yeah, I forgot to mention you really have to shove that wheel into the monitor face for a good polish.

I'd say don't worry about implosion, I used to worry about that until a friend of mine demonstrated that the front of a modern CRT (I wouldn't necesarily try it with a B&W television, or even a color TV for that matter) can be fairly arbitrarily smashed in with a hammer with no apparent hazard to the smasher. I used to fiddle around in the back of monitors to de-fuse them with a screwdriver in the sealing tip under the connector base, now I use the hammer-blow-to-the-face method and I think it's a lot safer. I think the back of the CRT is where any danger lies.

It's all on account of cuz the face has multiple plies including plastic, I figure.

-Jeff

And just letting the vacuum out doesn't necessarily discharge that huge Leyden jar, so still be careful.

Cheers! Rich