Degaussing CRT's

Discussion in 'Retro & Arcade' started by matz, Feb 24, 2019.

  1. matz

    matz Member

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    So I picked up an IBM 4863 (IBM PC jr display) but it has some color issues going on, it was cosmetically damaged in transit but I suspect it may need degaussing. See pics below:

    [​IMG] [​IMG] [​IMG]

    I've seen some pretty cheap degaussing wands around, anyone got any experience with these?
     
  2. mAJORD

    mAJORD Member

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    nice score!


    A Degassing wand is just a coil of wire, a switch, and a mains lead.. The only difference between them from a functionality point of view might be there field strength - which within reason is irrelevant.

    So apart from being shit quality, (and you might want to check it over for dodigness before plugging it in) , but for your occasional use Id say would be perfectly fine .. What's far more important to research if you haven't used one before, is technique using it.. you can potentially make it worse, or permanently damage the shadow mask

    keep it away from media and your mobile phone too unless you want a dead digital compass ;) - have perma killed a stand alone compass module mucking around before.
     
  3. elvis

    elvis Old school old fool

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    And a high wattage resistor. Don't go shorting active to neutral with a thick wire. :)

    I bought a Chinese-made degaussing wand eons ago, which itself was designed for a US market (US plug). Our 240V power here makes it get pretty hot pretty quick, so I only use it for a few minutes max before letting it cool down. I've also wrapped the thing top to toe and back again in thick insulation tape, just in case there are any cracks in the plastic housing.

    Mine looks identical to this:
    https://www.aliexpress.com/item/FRE...ine-kinescope-degaussing-rod/32639744634.html

    In general, I find problematic CRTs will need degaussing many times. I often do it on bad ones once every time I use the display, and then put up with whatever the result is. Over the course of weeks/months they typically settle down. Keeping your CRT away from magnetic sources and always in the same orientation (i.e.: facing north/south/east/west) for long periods of time also can help it settle too.

    When I degausse I like to circle constantly around the monitor, typically starting with the wand pointing at the centre and doing ever increasing circles around until I'm at a diameter of about twice the screen's dimension, then pause for a moment and start again. Don't leave the wand in one place, and don't concentrate on any one spot, even if tempted.

    Overall the geometry and sharpness of that display looks great. I think grab yourself a cheap wand, give it 30-60 seconds of a blast each time you power up. You'll find it'll go for a bit and come back later, but reduce over time.

    Good example here (video is sped up in parts, note the time on the display)

     
    Last edited: Feb 26, 2019
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  4. OP
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    matz

    matz Member

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    Thanks guys, I've ordered the wand and will update as I go.
     
  5. WuZMoT

    WuZMoT Member

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    I have a green square one, similar deal to elvis, US plug, gets hot quick.

    results vary, hopefully you can sort it out. I was working with a 'slim' consumer TV which are known to be shit so you will surely have better luck.
     
  6. nimmers

    nimmers Member

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    Just be careful with some of the cheap ones on eBay, they are meant for 110V and running them at 240V kills them pretty quick. I expect you probably have a step down transformer anyway.
     
  7. flain

    flain Member

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    The green square ones are pretty common on ebay from Chinese sellers, they literally just bend the US plug prongs so they fit in our socket and sell them as "for australia" lol
     
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  8. WuZMoT

    WuZMoT Member

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    mine actually came with the converter plug
     
  9. mR_CaESaR

    mR_CaESaR Member

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    I was given one of those cheaper ones and I use a converter plug. They're not the most solid connections in the world, but it definitely did the job for me.I had a massive discoloured section and after about 10 attempts at fixing, she came up good.
     
  10. qwertylesh

    qwertylesh Member

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    i got one of the $30 green ones off ebay with an au plug but it gets very hot very fast so i suspect it is a 110v model. Should i use a stepdown with it? I have one for regional consoles and if it will last longer with a stepdown then ill use that in conjunction with it from now on.

    anytime i move my arcade unit, I find that it needs a good degauss, if you transport crt's and esp if they ever are placed on the side or upside down it will affect the guassing of the screen, arcade screens and some monitors dont have the inbuilt degause ring you find on old school televisions, so correcting gauss on crt's these days is pretty normal since we most often hold onto the rarer and purpose specific crts.
     
  11. flain

    flain Member

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    I have one of those Chinese candy cab copies and had to degauss it pretty often it kept getting red blotches in the bottom corner. Turned out the speakers in the cab were not shielded at all. Once i replaced them with shielded speakers i haven't had to degauss it since.

    On using a step down transformer - sure if you have one but i wouldn't bother going out and buying one just for that. Inside a degaussing coil its pretty simple stuff, its just a coiled wire around a rod so as long as you aren't using it for long it should still work just fine on 220v (and if you are using it for more than a few minutes you're probably doing it wrong anyway). If your CRT is having a hard time degaussing look for other things in the room (speakers etc) and try changing it's orientation in the room while you work on it (sounds weird but works).
     
  12. OP
    OP
    matz

    matz Member

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    I suspect I've ordered the same cheap green square chinese ebay ones that everyone is referring to. I've got a step-down transformer, needed that to power the 4863 to begin with.

    The 4863 does have an internal speaker so I'll look into the shielding (or lack thereof) on that.
     
  13. Sir Didymus

    Sir Didymus Member

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    Just FYI, I bought one of the green wands myself a few weeks ago and it has an aussie plug and it says 220V on the box for what it's worth.
     
  14. elvis

    elvis Old school old fool

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    In China, it's worth the cost to print it, and not much more. :)
     
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  15. Sir Didymus

    Sir Didymus Member

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    that's about what I figured
     
  16. qwertylesh

    qwertylesh Member

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    The video is helpful, seems i been doing it wrong, been pulling away as i do the spiral out, but u dont need to.

    My screen doesnt gauss too badly only a little when its moved.
     
  17. elvis

    elvis Old school old fool

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    I tend to turn on the wand a few feet away, walk in, do the spiral, walk out, turn off the wand.

    While I'm doing the spiral motion, I'm about 1-2 inches from the screen max, but keep that distance consistent.

    I've heard anecdotally that turning the wand on/off too close to the screen isn't great (sudden magnetic field changes can yank on the aperture grill inside the CRT, apparently). That could all be total BS, I dunno. But I play it safe by starting and finishing from a bit of a distance, while doing the actual degaussing "spiral" at a consistent closeness.
     
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  18. qwertylesh

    qwertylesh Member

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    Great advice thank you :D
     
  19. flain

    flain Member

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    I've had a stubborn CRT before and had to ask for advice on aussiearcade forums because everything i did only seemed to make it worse. Someone suggested to flick the wand button (literally flick at the the button) from behind the tube. Fixed it right up for me :) degussing from the front wouldn't work for some reason unknown to me :).
     
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  20. elvis

    elvis Old school old fool

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    Magnetic fields are tricky things. Not being able to see them with the naked eye doesn't help.

    I've got one CRT that I have to come in from the side of the cabinet, behind the plane of the front of the screen, to fix a stubborn problem.

    I *love* CRTs. But even then I admit how much of a pain in the arse they are. :)
     

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