CRT monitor + super magnets

[Zepper]

A famous guy on YouTube has made an "experience" with an old (ready-to-trash) CRT monitor and super magnets. He approached the magnets into the screen and... well, you know all those distorctions of color and shapes.

I wonder if such thing is dangerous. Could someone comment it?

(video in portuguese)
http://www.youtube.com/watch?feature=pl ... Zk--_Rh738

[blargg]

Wow, those patterns are really neat. It's interesting how it magnifies the shadow mask pattern.

I don't see any danger, beyond ruining the monitor. At the very least, it'll magnetize the shadow mask in a way that perhaps the built-in degaussing coil won't demagnetize. It might also dislodge the mask due to the strength. It's behind really thick glass, so nothing will come through. I don't see any radiation danger either.

With the CRT open, on the other hand, there are lots of dangers. The biggest is implosion of the CRT, because the neck on the back is very thin. Waving a screwdriver around it without eye protection is careless. And then there's the high voltage stored in the capacitor the CRT itself acts as.

[lidnariq]

I recall being told that Trinitron tubes, since they use an array of metal wires in lieu of a solid shadow mask, are far more easily damaged by rare earth magnets like this.

The bit where he's waving a metal screwdriver around (probably) without having discharged it makes me nervous.

[rainwarrior]

My dad once waved a strong magnet around the computer monitor to see the funky colours. Afterward the monitor had a purplish area on it that was strong at first and slowly faded over months (it never totally went away).

[TmEE]

Only danger is shadow mask dislocation but that is very hard to achieve as it is attached to the glass on all sides. The mask is really quite strong too, it is hard to rip it apart or wrinkle. Trinitrons have that aperture grille system and a good shock is all it takes to give the tube permanent discoloration.
I have messed around with magnets on my old TV, and I did sometimes get some semi-permanent discoloration that faded with time... or I'd take a weak magnet and "pull it off the edge"... that worked really well haha

[James]

With the CRT open, on the other hand, there are lots of dangers. The biggest is implosion of the CRT, because the neck on the back is very thin. Waving a screwdriver around it without eye protection is careless. And then there's the high voltage stored in the capacitor the CRT itself acts as.

My friend and I worked at his dad's monitor repair shop in high school. Not surprisingly, for kids that age, we spent a lot of time destroying stuff that was beyond repair. CRTs are really hard to break from the front. The neck is comparatively easy to break, but I wouldn't necessarily say it's fragile; I don't recall one ever being non-intentionally broken. The little nipple at the end of the neck is really easy to break and there were at least a couple of times that I heard the telltale hissing after I, or someone else, hit the circuit board attached to the neck the wrong way. No implosion for that mistake, though.

Getting shocked by a non-discharged CRT really sucks, but (circumstantially, at least) it's not fatal. I'd say the biggest risk is probably the large electrolytic capacitors in the power supply section.

The only cases where I've seen 'permanent' discoloration is when a yoke was physically knocked out of alignment. Otherwise, discoloration that the internal degaussing coil couldn't fix could be resolved with an external, stronger, one. That said, I don't think we ever tried to intentionally damage a CRT with a super-strong magnet.

[Zepper]

Thanks for the comments, guys!

[mikejmoffitt]

Getting shocked by a non-discharged CRT really sucks, but (circumstantially, at least) it's not fatal. I'd say the biggest risk is probably the large electrolytic capacitors in the power supply section.

I do just want to point out that the tube itself acts as a large capacitor and the spot under the anode cap (...the anode) is the ouchy part.

If he knows what not to touch, the guy shouldn't be too scared waving the screwdriver around. CRTs are scary, but not as scary as they are often made to sound, especially not at such a small size. He'll be fine.

[noattack]

For those who like the aesthetics, in the 1960s, the artist Nam June Paik used to do all sorts of neat installation pieces involving CRTs and massive magnets.

[WedNESday]

My dad once waved a strong magnet around the computer monitor to see the funky colours. Afterward the monitor had a purplish area on it that was strong at first and slowly faded over months (it never totally went away).

I bet your dad was like;

'Hey son, look at this cool effect.'

...

'Uh oh...'

[rainwarrior]

Yeah, that's exactly how it went down.