PVM corner color issues not resolved by Degaussing coil?

[cr4zymanz0r]

So not too long ago I got a Sony PVM 20L2 with some color issues in 2 of the corners.
Here's a picture: http://i.imgur.com/Oq6CIGG.jpg

The worst is the top right corner, but the top left corner has a minor color issue as well. So here's what I've tried:

1.) Took the outer metal shell off to make sure nothing was obviously wrong/broken inside. I did find that a magnatized screwdriver had been electrical taped in the upper right part of the frame, but even after I removed it I couldn't really notice a change.
2.) Playing a game for an hour-ish and using the internal degaussing coil every few minutes. This hasn't improved it by any perceivable amount. It will cycle to the correct colors during the process, but once it's done it's back to the wrong colors
3.) Just got a professional degaussing coil/wand in today, tried it, no perceivable change. It says to only use it for a minute then let it cool for 30 minutes. Pretty sure I only used it for 20 seconds or less. maybe I need to go nearly the full minute for stubborn color discoloration. I'll probably try that after it's cooled down.

Anybody else got any ideas? I'm technically minded, but never really done much work on CRTs.

[Guspaz]

I can't view your images (blocked at work), but I've got a PVM-14L2 which had a discolouration (blue) and geometry distortion in the top-right corner. I taped some strip magnets to the tube and was able to pretty much completely solve the issue. Maybe a very slight degradation of convergence in that corner, but that's a tiny price to pay to fix the discolouration and distortion.

I posted an account (with photos) of adding the magnets here:

http://www.neo-geo.com/forums/showthrea ... ad/page184

You can see me at the start of that page complaining that the degaussing coil didn't help, and then me trying some weak circular magnets, and then me replacing them with the strip magnets.

[cr4zymanz0r]

Messing around with magnets inside does seem to make the issue better, but there's a big metal guard in the way of me getting to the places I really need to get to. I'm hoping I don't have to completely disassemble the PVM just to get that metal guard/support out of the way.

EDIT: I slid some magnet tape into the right places to get the colors mostly good, but then when i went to put the outer metal case back on it caused discoloration in the upper left corner again. Degauss doesn't make it go away, but if i take the metal shell back off and deguass then it goes away.

[Guspaz]

It'd be a bit time consuming, but you can try figuring out where to put the magnets such that the discolouration is resolved when the case is back on. Or try more/stronger magnets. As I said in my neogeo post, I needed six of the small magnets to fix my issue, but only two of the bigger magnets. I ended up going with three strip magnets because they were thinner, and I figured that the thinner the magnets on the tube, the more likely the tape would stay put.

[tjsynkral]

So not too long ago I got a Sony PVM 20L2 with some color issues in 2 of the corners.
Here's a picture: http://i.imgur.com/Oq6CIGG.jpg

The worst is the top right corner, but the top left corner has a minor color issue as well. So here's what I've tried:

1.) Took the outer metal shell off to make sure nothing was obviously wrong/broken inside. I did find that a magnatized screwdriver had been electrical taped in the upper right part of the frame, but even after I removed it I couldn't really notice a change.
2.) Playing a game for an hour-ish and using the internal degaussing coil every few minutes. This hasn't improved it by any perceivable amount. It will cycle to the correct colors during the process, but once it's done it's back to the wrong colors
3.) Just got a professional degaussing coil/wand in today, tried it, no perceivable change. It says to only use it for a minute then let it cool for 30 minutes. Pretty sure I only used it for 20 seconds or less. maybe I need to go nearly the full minute for stubborn color discoloration. I'll probably try that after it's cooled down.

Anybody else got any ideas? I'm technically minded, but never really done much work on CRTs.

That's way too much for strip/sticky magnets to cure, IME. You need to fiddle with the yokes. If you can find the service manual, follow the tube adjustment procedure from beginning to end.

[cr4zymanz0r]

Will adjusting the yokes work for my issue? I knew yoke adjustment can fix purity/color issues sometimes, but I was under the impression that was for when the whole screen was discolored, rather than a corner or two.

[viletim]

EDIT: I slid some magnet tape into the right places to get the colors mostly good, but then when i went to put the outer metal case back on it caused discoloration in the upper left corner again. Degauss doesn't make it go away, but if i take the metal shell back off and deguass then it goes away.

Do you mean if you run the monitor with out any extra magnets stuck to it and the metal shield removed then the picture looks fine? If so, it sounds like the metal shield has been magnatised.

[cr4zymanz0r]

Do you mean if you run the monitor with out any extra magnets stuck to it and the metal shield removed then the picture looks fine? If so, it sounds like the metal shield has been magnatised.

Not exactly. Here's a breakdown of the process:

1.) Discoloration in the upper left and right corners as seen in the original picture when I bought it.
1a) Bought and used a degaussing coil/wand, but it didn't make the issue any better.
2.) Took outer metal shell off, experimented with magnets. I was able to get the upper left corner 99% resolved with some craft magnet adhesive tape stuff. Upper right corner was able to get maybe 80% resolved using the same stuff.
3.) When I put the outer shell back on, it made the color messed up again in the upper left corner, and possibly the upper right corner to a small degree.
4.) Degauss, no help, remove shell and deguass and it 'fixed' it (while the magnets are still in place), put shell back on, same issue. remove again, frantically use degaussing coil on that portion of the shell (outer), little to no help. Try it again on the inner portion of the shell there and then it seemed to be fixed or mostly fixed. Not sure if that demagnetized that or I was just lucky.

I don't know if maybe some of the internal metal support/guards have become magnetized, thus causing the original issue. Using magnets vastly improved the issue, but it's still not fully resolved in the upper right corner. Good enough for now until I have some sound suggestions before I open up the beast again.

[mikejmoffitt]

If your yoke has slid back, you may have problems with it.

I had an 8" PVM with seemingly permanent discoloration damage from having been in a car trunk next to a speaker for six hours. Its degauss coil was unable to make a difference, but what DID help was holding it up face-to-face with a different CRT, and letting that larger monitor's larger degauss coil degauss both at once.

[Guspaz]

In that scenario, a proper external degaussing coil would have also worked.

[mikejmoffitt]

While that's true, I've never seen a good cheap degauss coil. In this case, it was the difference of $40 versus holding one monitor against another for ten seconds. Definitely worth a try before money is spent...

[Guspaz]

There are some good ones for not too insane amounts of money, although IIRC I paid something like $70 for mine (can't remember if it was CAD or USD). So certainly if the holding-against-another-monitor approach works, it's a decent substitute. I didn't have any other monitor, though, and had a stack of PVMs to go through, so I figured it would be handy.

[Pasky]

While that's true, I've never seen a good cheap degauss coil. In this case, it was the difference of $40 versus holding one monitor against another for ten seconds. Definitely worth a try before money is spent...

I just use two strong magnets taped to a corded drill. Easy degaussing coil.