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Old 04-16-2015, 07:00 PM
Electronic M's Avatar
Electronic M Electronic M is online now
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How to make a degauss coil for servicing out of a junk BPC TV

I think this is worthy of sticky status.

How many of us, especially newbies and those that rarely work on color sets have found our selves in the position of needing to degauss a screen manually, but not having a proper service degaussing coil?....Well I've seen enough to want to offer some help.

You can find junk 80's and newer BPC sets for dirt cheap to free at the curb everywhere these days. Most 20" and up use an over sized degauss coil, and I'm going to show you how to make that into a convenient servicing coil.

The above photos show a degauss coil pirated from a 20" BPC set, and a quarter for size, and the same two objects with a vintage servicing degauss coil for comparison.

Start by un-looping the original and smoothing out the corners.


Then fold it into three turns.


Pull it smooth and uniform, and wrap it in couple of spots with electrical tape to hold it like that.


Notice how it is the same diameter as the service coil (the two I've done are both like that)?


Then put one even layer of electrical tape around/along it to encapsulate it, and add a cord. If you want you can add a switch too.

Note: the copper in the photos below is an isolated extra winding I added over the layer of electrical tape to make the coil into an air core transformer for an experiment to test an idea I had...If I unwrap that copper a normal black degauss can be found underneath. When I can I'll add or replace those pictures with a better representation of the finished product.


This is not as good as a proper service coil in that it gets hot in 1-5 minutes, and could pose a fire hazard if left plugged in after that. In most degauss jobs I do I only need 30 seconds to a minute, so this is enough to get the job done, and I HAVE used it a few times. When using it keep a hand on it at all times* it is plugged in to make sure it is not overheating. *except when it starts to get too hot to hold, at that point drop it and unplug it immediately.
If you did not get the degauss job done before overheat just unplug the coil let it cool well and do it again....Or go out and buy a proper servicing coil.
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Last edited by Electronic M; 03-23-2017 at 12:25 PM.
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Old 04-16-2015, 10:26 PM
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I was wondering if this sort of thing could be done since I saw the link to a coil on eBay.

I think a momentary switch would be a good addition to this one.
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Old 03-23-2017, 12:27 PM
Electronic M's Avatar
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Quote:
Originally Posted by Jon A. View Post
I was wondering if this sort of thing could be done since I saw the link to a coil on eBay.

I think a momentary switch would be a good addition to this one.
I agree. It would probably be best to tape wrap it onto the coil so you can hold it with the coil.
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Old 03-23-2017, 05:34 PM
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Ah yes, easy one-handed operation.

I'd like to add that it is important to use an *oversize* coil as Tom instructed. A while back I used a coil from a 19" set that was only big enough to surround the CRT as it was all I had. Even at a lowered line voltage, it pegged the meter on my Powerite and got too hot to hold in about 10 seconds. It's a wonder it didn't trip the breaker.

By the way, I've heard of using a 100-watt light bulb in series with the coil as a current limiter.

Last edited by Jon A.; 05-10-2017 at 05:35 PM.
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Old 08-10-2017, 01:28 AM
tubetwister tubetwister is offline
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Quote:
Originally Posted by Electronic M View Post
I think this is worthy of sticky status.

How many of us, especially newbies and those that rarely work on color sets have found our selves in the position of needing to degauss a screen manually, but not having a proper service degaussing coil?....Well I've seen enough to want to offer some help.
That could be useful if you ever tried to find a cheap service degauss coil today ,then you know

For my #1 TV I use a retina searing 2016 4K HDR 1000+ 1474 NIT 7000:1 contrast panel code binned SUHD QDOT Samsung UN 55 KS 8000 LCD in my inner groove and a tamer 2015 Sony Triluminos 4K HDR LCD in the family cinema room and 1080p LCD around the home .

I benched TV's & radios part time from 1967-1970 at a Magnavox AD and studied electronics concurrently (3 yrs) but an unrelated career that retired me well with surplus $$$ and so on.

No hobby CRT here but I can't say I wouldent mind a bonded safety glass color roundie out back .I had a used 21" RCA round delta gun with a newer RCA colortron CRT in the early 70's and it wasn't bad until the PCB's started crumbing fatally

ON topic
That said I've used a Weller soldering gun sideways ,then walked back like a conventional decausss coil on a late model philips CRT to take a large purple /green spot out of the screen from a magnetized shadow mask for a friend's secondary TV from unshielded speakers too close and it worked

Last edited by tubetwister; 08-10-2017 at 02:07 AM.
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