Color Classic CRT Magnetic Issue

[just.in.time]

I have a Color Classic CRT that suffered some magnetic damage in shipping.  Does anyone have any tips for degaussing the CRT after heavy magnetic damage?  I have tried using the transformer from a NES console plugged into an extension cord.  While I am doing the swirls in front of the screen the magnetic damage mostly disappears, but as I slowly back away the damage returns.  I don't own an official degaussing wand, and would like to avoid purchasing one for a one-time-use situation.

 

[Byrd]

I’ve never had luck luck with DIY degaussing, and if done incorrectly it can damage it more and make it difficult to reverse. Proper CRT degaussers are cheap (and nasty - I had one melt in my hands!), I would however recommend the “green one” and a useful tool to have in any vintage electronics toolbox.

 

[Franklinstein]

Nothing is as good as a proper tool, but I've had to use a small round permanent magnet to demagnetize a couple screens (do NOT lean a modern laptop against the front of a CRT-based computer!) and it worked for the most part. The magnet was just barely more powerful than the average flat refrigerator magnet and it took a bit of trial and error and a few repeated attempts before it seems to have mostly cured the problem. So if you are up to take the chance and can't find a proper degausser, try a fairly weak permanent magnet. You'll know it's having an effect as the screen reacts to the magnet. Don't get too close, just a little closer to the affected area after the distortion disappears and then kind of swirl the magnet around a little.

 

[just.in.time]

Okay, I’ll give a weak magnet a try in the next day or so. If that doesn’t work then I’ll try to hunt down a degausser.

 

[Byrd]

Sometimes the weak magnet (not a hard drive magnet!) appears to work but nothing “sticks” when you withdraw it from the screen. However, unlike other DIY methods it probably won’t harm the CRT. Remember to degauss like you’re spinning fairy floss; start centrally spinning then as you spin to the outside of the screen lift your hand up more and more.

 

[techknight]

the aperture grille likely shifted in transit. Only solution is to replace the CRT. 

This is assuming that the degaussing circuit still works internally. When you flip the power switch and powerup the machine after a long rest, you should hear that "kick"

 

[just.in.time]

the aperture grille likely shifted in transit. Only solution is to replace the CRT.

I actually do have a Color Classic picture tube that suffered that damage. I think there is a thread somewhere here from 2016 as we diagnosed that. That particular tube had the colors messed up very uniformly across the entire display.

This particular tube is different in that sections are 100% fine while the upper left section has the messed up colors. Definitely reminiscent of an old TV where someone holds a magnet too close.

 

[Johnnya101]

A degaussing coil is $10 on ebay. Cheap enough to give it a try.

 

[techknight]

I actually do have a Color Classic picture tube that suffered that damage. I think there is a thread somewhere here from 2016 as we diagnosed that. That particular tube had the colors messed up very uniformly across the entire display.

This particular tube is different in that sections are 100% fine while the upper left section has the messed up colors. Definitely reminiscent of an old TV where someone holds a magnet too close.

Yep because that corner may have shifted. 

Anyways, You can use a power transformer with a nearly short-circuit load on it, or you can use a pull-trigger soldering gun (you know, the big ones). when you bring it near the CRT it will flutter in colors. Slowly move it in front of the CRT in a circular pattern for a few rounds. Then, keep doing this while slowly backing away. 

That will fix it if its a magnetic issue.