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Degaussing coil fixed my Color Classic

mraroid

Well-known member
Folks...
 
I converted my Color Classic to 640 X 480, and installed a board who's CPU I replaced with a full 68040,  I have a SCSI2CF for a hard drive, and I can boot to 7.6.2 or to 8.1 It boots kind of slow because I have a 128 MB SIM in it, but I am OK with that. I have a network card installed and I can surf the internet as long as I go to web sites made for older computers like mine. The Color Classic has been working perfect since I made the mod about 3 or 4 years ago.
 
But in the last 6 months or so, I saw a shadow on the left hand side of my screen and also on the right hand side. I have enclosed a photo (very poor, sorry) with a circle around the two shadows.  Many years ago I bought a NOS Sony replacement CRT.  But I did not want to switch over.  I am not sure how to line up the yoke and the screen.  I took a gamble and bought a degaussing coil on ebay. 
 
It just arrived and I used it.  Now my screen looks perfect!!  I have booted to 8.1 as well as 7.6.2.  I love that Sony CRT.  It was a high end screen in it's time, and I would never swap it out for a flat screen.  I love the look of a CRT.
 
The degaussing coil cost me around $40.00, but it was money well spent.  You can buy a very cheap degaussing coil if you want to, but I wanted one like I remember from my youth.
 
Now my Color Classic screen looks perfect.  I am so happy.  And I did not have to take anything apart to fix it.
 
mraroid
shadow5.jpg

 

techknight

Well-known member
I am going to be honest with you, I have never ever seen a degaussing coil go bad. 

Thermistor though? all the time. 

So this is an interesting one for me. 

 

mraroid

Well-known member
Hi techknight....
 
Are you saying that the color classic has a built in degaussing coil?  If so, then mine is broken I guess.
 
The CC must not need to be degaussed very often as this is the first time I have ever had to do it.  I did it on some older CRT TVs when I was younger.  But after a while most CRT TVs came with a degaussing coil that would run every time you turned the TV on.  It was a thick loop of wire that was arranged around the perimeter of the screen. The coil usually makes a braaap sound when you first turn it on. 
 
I do not recall hearing that sound from my CC. 
 
mraroid
 
 

techknight

Well-known member
Yea the CC has a Degausser. all Color CRTs do. they have to. 

9 times out of 10 its usually solder joint related, or the thermistor goes bad. 

 

mraroid

Well-known member
Can you post a photo of where the soldering joints are that could go bad?  Are they on the yoke (the thing that plugs into the back of the CRT)?  Or they on the board them selves? 

Is a drawing or a schematic on line any place that I could look at?

I would like to fix mine if I can.  Now I do not know how long the built in degausser coil has been bad in my CC.

Thanks for the heads up!

mraroid

 

techknight

Well-known member
I dont have any photos handy. But there is a black coil of wire that surrounds the bell of the CRT towards the front. from that, is 2 wires that go into a white molex connector. 

That molex connector then plugs onto the analog board. Right next to the analog board connector is a black square thing. That is the thermistor. If you flip the analog board over, you could potentially have bad solder joints at the molex connector for the degaussing coil, or the thermistor. It is also possible the thermistor is bad, and typically are hard to find. I dont have a part number handy to find a replacement for that currently. 

 

mraroid

Well-known member
Ah!  Yes, I do know what you are talking about.  The coil of wire for a big CRT TV is massive compared to what is in the CC.  I know the wire and molex connector you are talking about now.  I will open up this bad boy and see what I can find.

Thanks so much techknight!

mraroid

 

claanu

Well-known member
I have a Color Classic with these spots. Thought it was burn-in at first. Fair to say I should look at the molex connector solder and / or the thermister? I'd rather not buy a degaussing coil. :)
 

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Byrd

Well-known member
Reflow what you can, including the wires hidden under the little grey plastic flaps midway on the neck of the CRT (top and bottom). The adjustment pots can also corrode so clean all these with electronic solvent/lube and exercise the dials a bit.

If the CRT had high hours, sometimes it just wears out. The CC already does degaussing automatically, but check degaussing wiring is in its proper place. A CRT with poor degaussing usually has wavy colours or blotches of colour that don’t go with lots of use. You can DIY a degaussing device with a strong magnet (think from an old hard disk), but I doubt this is your issue.
 

davidg5678

Well-known member
You can DIY a degaussing device with a strong magnet (think from an old hard disk), but I doubt this is your issue.
I have tried this before, and even if you know what you are doing, it is easy to make things way worse. Keep strong magnets away from crts! :) I think that using a real degaussing coil (either by fixing the internal one or by purchasing an external one) is by far the best way to go.
 

Byrd

Well-known member
I have tried this before, and even if you know what you are doing, it is easy to make things way worse. Keep strong magnets away from crts! :) I think that using a real degaussing coil (either by fixing the internal one or by purchasing an external one) is by far the best way to go.

I agree, not my best advice but a degaussing wand also takes technique to use, a magnet can only make things worse if used like a wand due to less control of being able to turn it on and off.
 

claanu

Well-known member
Reflow what you can, including the wires hidden under the little grey plastic flaps midway on the neck of the CRT (top and bottom). The adjustment pots can also corrode so clean all these with electronic solvent/lube and exercise the dials a bit.

If the CRT had high hours, sometimes it just wears out. The CC already does degaussing automatically, but check degaussing wiring is in its proper place. A CRT with poor degaussing usually has wavy colours or blotches of colour that don’t go with lots of use. You can DIY a degaussing device with a strong magnet (think from an old hard disk), but I doubt this is your issue.
Hmm, interesting you mention the pots. I don't think this is a high-hour CRT, but I did just notice that three color adjustment pots on the back of the AB do absolutely nothing, not even after a good cleaning. I'll replace them and check the other solder and see where I end up.
 
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