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CRT ADC Display Badly Magnetized

bunnspecial

bunnspecial

macrumors G3
Original poster
May 3, 2014
8,390
6,564
Kentucky
I think at least that this is the issue with this one.

With the default Tiger background, the upper right hand corner of the screen is very noticeably green.

I've done the built-in degauss multiple times, as well as running the built-in color calibration and the spot remains. Short of trying to manual degauss it, can anyone think of what other things I could do?

I used to deal with these problems all the time, but it's been a long time since I've used a CRT extensively and I'm trying to come back on my old knowledge. I've also never had one where the built-in degauss didn't clear up a problem like this(including ones were I'd intentionally magnetized them).

I'm also attaching a screen capture for reference

IMG_1565.jpg IMG_1569.jpg Picture 1.png
 
I just spent a few minutes trying to manually degauss with my soldering gun, but there was no change. I'm suspecting that maybe it's a problem with a misaligned gun or something along those lines.

Does anyone have any ideas?
 
This is WAY over my head. My dad was an electrical engineer and the only advice I ever got from him about CRTs was never to open them!
 
eyoungren said:
This is WAY over my head. My dad was an electrical engineer and the only advice I ever got from him about CRTs was never to open them!
Click to expand...

I value my life too much to mess around with them too much internally :)

Those things have some BIG capacitors in them.
 
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Assuming that the display is badly magnetized. One way I use to fix crt displays is to turn them on then back off again until the discoloration goes away, but I don't know how good that is for the display itself.... Sometimes it does go away on its own though
 
Looks like the Aperture Grille got magnetised somehow. I had a Sony FD Trinitron develop a similar problem while under warranty back in the last century.

Try unplugging it from the mains for half an hour or so, usually gives the degauss a bigger kick.

That Sony (G400 IIRC) had the noisiest degauss I ever heard. Made a very loud "DONK" noise everytime it powered on. You could hear it on the floor below.
 
Thanks guys.

The seller responded and advised me to leave it turned on for 24h.

I have it hooked up to a DA(I wasn't going to risk a Cube PSU/VRM for that long!) set to not sleep and not turn the display off, along with the built in "jellyfish" screensaver. I'll see what it looks like this time tomorrow.
 
Does that discolored area move around on the screen at all?
Are you certain that the magnetized area is NOT caused by the location of other electrical devices, or intense magnetic fields? I still have a nice set of AR speakers that make a CRT go crazy if they are within 5 feet of the display.
Turn the display 90 deg.
Also, move to another location, 5 or 6 feet from its present location.
Unplug the power cord, then plug back in to assure that the degaussing circuit fires on the next power on.
Do that power reset each time you move the display.
 
DeltaMac said:
Does that discolored area move around on the screen at all?
Are you certain that the magnetized area is NOT caused by the location of other electrical devices, or intense magnetic fields? I still have a nice set of AR speakers that make a CRT go crazy if they are within 5 feet of the display.
Turn the display 90 deg.
Also, move to another location, 5 or 6 feet from its present location.
Unplug the power cord, then plug back in to assure that the degaussing circuit fires on the next power on.
Do that power reset each time you move the display.
Click to expand...

The spot is consistent. I've now tried it in two different rooms and in several different locations, and it's always there and always in the same space. Even when I was waving my soldering gun across the screen, I could still tell that the area was "different" as the colors distorted differently than the other parts of the screen.

As for powering it on and off-that sort of hard to do as this is an ADC monitor and gets its power through the computer. Even using an A1006, it won't power up independently of the computer.
 
Wow, I've never seen a CRT in that bad of shape.
Note: I am typing this comfortably from my PowerBook G4 :D. running Leopard. On 512MB of RAM.
 
128keaton said:
Wow, I've never seen a CRT in that bad of shape.
Note: I am typing this comfortably from my PowerBook G4 :D. running Leopard. On 512MB of RAM.
Click to expand...
Yeah that CRT is pretty bad, hopefully you can get it working! And Keaton how's it doing on the new forum??
 
I checked this morning before I left for work(roughly 12 hours with the screen saver on) and even degaussed it again for good measure. I'm going to let the full 24 hours that the seller suggested run their course, but I'm not overly hopeful.

I just hope that the seller makes right on this. I'm embarrassed to admit it, but I'm over $100 into this monitor by the time I bought it and paid for shipping. It was working fine before shipping(the seller sent several recent pictures) so I'm extremely disappointed.

I'll also try the soldering iron degaussing again this evening and see if that helps. I have an actual, proper monitor degaussing coil somewhere, but it's been so long since I've needed it that I have no idea where it is. I guess I could always try my home-built watch demagnetizer.
 
Gamer9430 said:
I think your going to need something just a bit more powerful, lol.
Click to expand...

I don't know, I over-engineered the thing a fair bit :)

It's actually just a straight walled kitchen glass wrapped with a couple hundred turns of 28 gauge enameled wire(I did a pretty darn good job of it, too, if I do say so myself-it took me about 3 hours to get it as nice as it is) and powered by a Lionel train transformer. I put the watch in the glass, raise the voltage, and then slowly lower it back down to zero. It's the same principle as a CRT degausing coil-it's a 60hz magnetic field that slowly decreases in intensity. I actually like it better than some of the commercially available ones, as the "open" design and the glass help to conduct heat away from it fairly fast and it stays relatively cool.
 
I gave the seller their requested 24 hours running at full brightness with a screensaver, and no change. We'll see what happens.
 
bunnspecial said:
I gave the seller their requested 24 hours running at full brightness with a screensaver, and no change. We'll see what happens.
Click to expand...
That sucks, Bunn. This reminds me of the video on YouTube of someone taking a massive and powerful magnet and seeing what happens when it's placed near certain things, like a CRT.

Also, perhaps someone hung a hard drive to the side of the monitor with Magnets, I would check to see if that may be the case... ;)

EDIT: here's the link-
 
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Gamer9430 said:
That sucks, Bunn. This reminds me of the video on YouTube of someone taking a massive and powerful magnet and seeing what happens when it's placed near certain things, like a CRT.

Also, perhaps someone hung a hard drive to the side of the monitor with Magnets, I would check to see if that may be the case... ;)

EDIT: here's the link-
Click to expand...

Thanks-that was absolutely hysterical!

Interestingly enough, back in my younger days when I was bored I used to wave HDD magnets over my monitor and then hit the degauss to clear them up. I always remember getting the exaggerated dot like you see in this photo from the shadow mask, although I suppose you won't necessarily get them in a Trinitron/Diamontron tube since they don't have a discreet shadow mask like cheaper monitors.

I do have access to a couple of superconducting magnets at work. The weakest one is 9.4T(400mhz 1H NMR), and the strongest 16.3T(700mhz 1H NMR). These are about 4 orders of magnitude stronger(or 10,000x stronger) than a refrigerator magnet. I could always wheel the monitor in and see if I can get it messed up enough that a degaussing might straighten it out.

Of course, I run the risk of forcing a magnet quench, and I don't think the NMR manager would be very happy with me if that happened :) . Not only does it mean a weak or two of downtime plus an expensive service call and the possibility of damage, but also a couple thousand dollars of helium-quite literally-up in smoke(or steam, more correctly). Some folks from biology a few years back(before I arrived in the department) got a crescent wrench stuck on the side of our old 500mhz magnet, and the facilities manager ended up doing a controlled quench because he couldn't get it off and it was causing serious field homogeneity problems. Biology was not allowed back in our NMR labs for a while!

And, just for fun and to show what I'm talking about, here's a Youtube video of a(controlled) quench when a magnet was decommission.

 
MacCubed said:
Also isn't it possible that the discoloration is due to a drop or shock during shipping?
Click to expand...

I feel like I've pretty well ruled out a magnetic issue in the shadow mask, so it's entirely possible that it's either a gun or coil alignment problem. If that's it, it may be fixable but it's a. not worth it to pay to have it fixed and b. trying to fix it myself may make the problem worse, and carries the possibility of serious injury or death.
 
bunnspecial said:
I feel like I've pretty well ruled out a magnetic issue in the shadow mask, so it's entirely possible that it's either a gun or coil alignment problem. If that's it, it may be fixable but it's a. not worth it to pay to have it fixed and b. trying to fix it myself may make the problem worse, and carries the possibility of serious injury or death.
Click to expand...
Are you going to fix it, return it, or just keep it since shipping would be really high?
 
MacCubed said:
Are you going to fix it, return it, or just keep it since shipping would be really high?
Click to expand...

I'll have to let the UPS insurance process run its course. If they end up paying out and telling me to keep it(which probably has about a 50% chance of happening based on past experience) I'll try to fix it. Otherwise, I'll let UPS do whatever they do with it.

If I do tackle it, I'll need to dig out my plastic screwdrivers and all my other old CRT tools. I also use to have a really nifty discharge tool that plugged into earth ground in an outlet and that you would(using one hand) work under the anode on the top of tube. I always wore a leather glove and stood on a rubber mat, but it still always scared the crap out of me.

Of course, with anything like this, you always keep one hand in your back pocket while you're working! Standing on a rubber mat and of course rubber or leather gloves(along with plastic tools) are always a great idea too.

CRTs deserve a healthy amount of respect.
 
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