Reviewing a cheap CRT degaussing wand

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Hi all. This post is a review of the cheap "green stick" CRT degaussing  
wands, as I haven't found much discussion of them and some other  
repairers of vintage monitors may find it useful.

CRT degaussing tools seem to be hard to find these days. Occasional used  
ones come up for sale, and there are still some to be found in the US.  
However, in the UK they're near-unobtainable. The main source seems to  
be eBay sellers in China, all of whom are selling the same type: a wand-
style degausser in a green plastic shell. So, having a couple of CRTs  
with purity problems, I bought one to see if it would do any good.

The wand cost about 15 GBP and arrived within a couple of weeks. There  
was no documentation included, leaving me with just the specs given in  
the eBay listing, which read:
-Relative magnetic field: 70MT
-Load current: 1A
-Working hours: 20 seconds
-Power: 220V
-Specifications: About 31*31*200(mm)

The outer shell is some soft semi-translucent plastic (polythene?), and  
feels extremely cheap. A momentary switch pokes out of the top of the  
casing (a momentary switch is good, as it stops me accidentally leaving  
the coil energised).

The wand came with a moulded two-prong plug, which I had to cut off to  
fit a UK plug. And... I have never seen mains cable that thin before. It  
is, at least, double insulated, but the conductors are at most 28AWG and  
possibly even thinner (it's hard to measure stranded cable, but the  
diameter is somewhere around 0.25mm to 0.35mm). The strain relief clamp  
in the UK plug wouldn't even hold the cable until I wrapped some extra  
plastic around it. Oof. Looking at the ampacity ratings on the Wikipedia  
article for American Wire Gauge, that cable must be very close to, if  
not exceeding, its recommended current rating. It feels worryingly  
plausible that someone, somewhere made the calculation "it's fine, if  
they push the button for too long the coil will burn out before the  
cable insulation melts".

However, the tool does what it's supposed to and noticeably reduced the  
blotches visible on the CRT display. I used the standard technique of  
powering the coil from a couple of metres away, bringing it up to the  
CRT face, circling it around a couple of times, then smoothly backing  
away two or three metres before switching off again. I definitely  
recommend sticking to the stated maximum of 20 seconds continuous  
operation and letting the wand cool fully before using it again. The  
heat seems to take a few seconds to conduct to the outside of the  
casing, so it's not until after you've switched it off that you feel how  
warm it's really getting.

I popped the end cap off the casing to take a look inside, but haven't  
disassembled it further. Strain relief is just a knot in the mains  
cable. I don't see any current limiting apart from the coil itself. The  
coil is wrapped around a core of steel plates, and seems to have some  
more plastic insulation around it. The non-business end of the coil  
seems to have some copper mesh shielding. Hooking the whole thing up to  
a component tester, coil resistance measures around 140 ohms, with an  
inductance of 320mH.

In summary,

Pros:
- Cheap.
- Does what it's supposed to.

Cons:
- Not particularly sturdy.
- Probably not the safest thing ever, use with caution.

If there were better-quality tools available, I would definitely buy  
those instead. But there weren't, and this one did at least provide the  
functionality I needed.

HTH,
Rayner

--  
Big-8 Management Board: https://www.big-8.org
Homepage: http://magic-cookie.co.uk

Re: Reviewing a cheap CRT degaussing wand
On 2021/01/12 12:48 p.m., Rayner Lucas wrote:
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...

I use a large Weller Soldering Gun when I can't find one of the  
degaussing coils in the shop...

John :-#)#
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                      John's Jukes Ltd.
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Re: Reviewing a cheap CRT degaussing wand
snipped-for-privacy@flippers.com says...
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I also used the Weller or what ever Gun I had handy on the old CRTs.

Just about any coil of wire will work that does not draw too much  
current.



Re: Reviewing a cheap CRT degaussing wand
snipped-for-privacy@earthlink.net says...
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Oh, that's a neat idea, I never thought to try a heating coil. I did  
consider making my own, but with no idea what spec to aim for, buying  
one seemed like it had a better chance of success :-)

Rayner

--  
Big-8 Management Board: https://www.big-8.org
Homepage: http://magic-cookie.co.uk

Re: Reviewing a cheap CRT degaussing wand
On 2021/01/12 4:56 p.m., Rayner Lucas wrote:
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You need something that puts out a large AC field - like the unshielded  
transformer used in soldering guns.

An electric heating coil has a very small magnetic field, I'd say it was  
most unlikely to be useful for degaussing...

John :-#)#

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Re: Reviewing a cheap CRT degaussing wand
snipped-for-privacy@flippers.com says...
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Ah, thanks, I get it now! I don't have a soldering gun, but it would  
certainly have been a lot easier to find one for sale than a degaussing  
coil. Or I guess I could've looked around for something else with a  
transformer I could salvage.

Rayner

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Big-8 Management Board: https://www.big-8.org
Homepage: http://magic-cookie.co.uk

Re: Reviewing a cheap CRT degaussing wand
John Robertson wrote:
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**  Utter nonsense.  

 Such trannies radiate SFA mag fileld.  


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**  But that is  *not* what a soldering gun loop is.  

Single turn sure  -  but a carrying about 250 amps !!.

So, at close range the same as a 25 turn coil carrying 10 amps.

Much like the example I posted earlier that WORKED like a treat.  



......  Phil  




Re: Reviewing a cheap CRT degaussing wand
On Tuesday, January 12, 2021 at 10:47:08 PM UTC-8, John Robertson wrote:
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Some soldering guns use a hairpin winding on a toroid core; those do NOT give
external field, they're self-shieding, but a 5" diameter simple wire loop connected instead of the
short tip will do a degaussing task adequately.

Re: Reviewing a cheap CRT degaussing wand
 whit3rd wrote:

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**  I have read that a magnet attached to the chuck of a power drill, running at high speed, can also be used to demag a TV tube.  

   Never tried it  -  seems a bit dodgy.  



......    Phil  

Re: Reviewing a cheap CRT degaussing wand
On Sunday, January 17, 2021 at 12:34:53 AM UTC-5, snipped-for-privacy@gmail.com wrote:
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I can envision some Einstein attaching a magnet to a drill with cellophane tape, and watching in stunned horror as the magnet flies off and smashes the glass top coffee table..




Re: Reviewing a cheap CRT degaussing wand
On 2021/01/17 2:02 p.m., snipped-for-privacy@gmail.com wrote:
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You think? Seems an understatement for you, Phil...

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Or explodes the picture tube!

John :-#(#

--  
(Please post followups or tech inquiries to the USENET newsgroup)
                      John's Jukes Ltd.
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Re: Reviewing a cheap CRT degaussing wand
snipped-for-privacy@flippers.com says...
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cellophane tape, and watching in stunned horror as the magnet flies off  
and smashes the glass top coffee table..
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I used to walk to school (in the 1950s) beside a canal in Bristol (UK).  
There was a girder footbridge over this canal, and small kids had  
somehow acquired duff CRTs and would carry them half across this bridge  
in order to watch them smash into the water. Happy to say I never  
actually saw a child burst one on the girders...

Re: Reviewing a cheap CRT degaussing wand
Mike Coon wrote:
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**  One saw a pic of a B&W picture tube that had imploded.  
 The electron gun had been propelled though the screen and imbeded itself in the back of a lounge chair.  

There is almost 20,000lbs of pressure on the out side of a 23inch one..  

......  Phil  

Re: Reviewing a cheap CRT degaussing wand
[snip]

Back, umm... 1977ish.. (*whew*) I took a
slotted steel wallmount bookcase rail
(about 1/4 by 1/2 inch by 4 feet), wrapped
some, umm, probably #18 lampcord around  
it, and wired it to a 12VAC transformer.

I added in something like a 50 watt 120vac
lamp (lighbulb) in series as a current
limiter.

Yeah, I had no idea what I was doing.

Anyway, I then plugged this into a 120VAC
power strip, put on some safety gloves
and goggles, held it near the tv, and
had my friend turn on the power strip.

It worked!

1990ish I used a handheld Radio Shack brand  
tape degausser for the same purpose.  And
yes, it worked, too.

So these things are doable...



--  
_____________________________________________________
Knowledge may be power, but communications is the key
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Re: Reviewing a cheap CRT degaussing wand
https://www.zoro.com/gc-electronics-specialty-tool-degaussing-coil-9317/i/G
2187702/    

https://www.travers.com/portable-magnetizerdemagnetizer/p/57-081-121/?gclid
=Cj0KCQiA0fr_BRDaARIsAABw4Etup-m1bJ4WR6u5u86ELikWOl0rDsERXNjJ6Tsio0439R18
RN6wxGgaAqo7EALw_wcB    

https://www.ebay.com/i/123990657206?chn=ps&mkevt=1&mkcid28%

Guys and gals - these things are available OTC here in the US. Why not in t
he UK? Oh, but they are:

https://www.bartington.com/degaussing-wand/

https://www.ebay.co.uk/itm/NEW-CRT-MONITOR-DEGAUSSING-COIL-Arcade-TV-Repair
/123990657206?hash=item1cde6b48b6:g:CkcAAOxyKsZRwenD    

For a one-off use, I would likely stick to the soldering gun - does the tri
ck, even if used "off-label". I bring my 100/300 watt Craftsman gun to Kutz
town for the occasional chassis connection, and it is as often as not borro
wed by the TV guys for cleaning up the old TV pictures, but seldom for sold
ering.  

But if I had to do this every day, or even every week, I would likely inves
t in a purpose-built device from a reliable maker and reliable source. As I
 am fond of writing: The Internet is your friend!  

Peter Wieck
Melrose Park, PA

Re: Reviewing a cheap CRT degaussing wand
snipped-for-privacy@gmail.com says...
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I thought most crt screens had a coil around then that helped degauss  
them every time they are turned on.  Unless someone puts a magnet near  
the screen I doubt that many would need degausing.

With almost everything switching to the flat screens there is probably  
very little need for a dedicated degausing coil unless your shop  
specilizes in restoring old electronics.  Hard for me to see any shop or  
one doing much work would not have a soldering gun that could be used.  
Maybe many do not know the soldering gun could be used.

Re: Reviewing a cheap CRT degaussing wand
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They do. And, whereas I am not in the vintage CRT hobby, there are any numb
er of applications and any number of reasons why the on-board degausser may
 not be there,  adequate, or even functional. There was (RIP) an individual
 not far away whose hobby was restoring video arcade games - commercial gra
de - with the big Curtis-Mathis CRTs in them. And he had half-a-dozen (at l
east) degaussers of various types and natures that he used regularly. But,  
apparently, failure of the on-board degausser was common enough that he was
 prepared.  

I keep some small, but very powerful magnets with me most of the time - is  
that painted pipe steel, copper, or possibly something else? Or that light  
can? What grade stainless *might* that be? And they will stick to most flat
-screens - but not cause any distortion.  But get one within 10" or so of t
he big Sony 32" CRT TV (c. 2001) at home and watch the show. Of course, the
 on-board coil works on that one, still.  

Peter Wieck
Melrose Park, PA  


Re: Reviewing a cheap CRT degaussing wand
 Ralph Mowery wrote:
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** Correct =  ALL  crt colour TVs and monitors have automatic degaussing at switch on.  
Most monitors have user operated de-gaussing as well.  

TV techs may need a de-gausser for that rare event you mentioned .

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** Such guns are getting hard to find.  
 Demand is so low, few wholesalers stock them.  

.....  Phil  

Re: Reviewing a cheap CRT degaussing wand
snipped-for-privacy@gmail.com says...
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Except for the shops that restore old devices with CRTs in them I doubt  
that very many shops even work on the CRT units.  You can buy some of  
the newer LCDs for what it would cost for many shops to look at the  
older sets of the same size screens.  I am not sure if any TV sets that  
had the CRTs in them are even capabile of the new format of the TV  
signals with out a converter.

  I do know of one man and wife that still use the old set with the  
satalite dish.  To top it all off he was an electronics engineer with  
the Bell and Western Electric system.  He is 80 years old and somehow  
seems to mostly be stuck in the years before transistors.  He is a ham  
radio operator and has much gear produced from about 1930 to 1970  and  
can work on that with no problem.  

Local wholesellers may not stock them,but there are plenty on the  
internet.  Even Home Depot has them for about $ 45.  About 5 years ago I  
bought just the replacement housing for a gun I have had over 50 years.  
I had dropped it several times during that time and the last time  
finished off the housing.  As just a hobbiest I do not use one very  
much, but do not see how I could get along with out one.  I do use the  
SMD rework hot air and small iron most of the time.

You did jog my memory. I remember monitors that had the degauss switch  
on them.  They probably put that on them as many of the computers did  
have speakers with magnets close to the screen.  



Re: Reviewing a cheap CRT degaussing wand
 Ralph Mowery wrote:
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**  Never seen a PC speaker that did NOT use shielded magnets on the drivers.  

 FYI  Consists of a second ferrite ring magnet to cancel external fields - plus  a steel cover..  


.....  Phil  

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