| Reviewing a cheap CRT degaussing wand [message #404116] |
Tue, 12 January 2021 15:48  |
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Originally posted by: Rayner Lucas
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
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| Re: Reviewing a cheap CRT degaussing wand [message #404117 is a reply to message #404116] |
Tue, 12 January 2021 17:00  |
John Robertson
Messages: 17
Registered: July 2012
Karma: 0
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Junior Member |
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On 2021/01/12 12:48 p.m., Rayner Lucas wrote:
> 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
....
>
> 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
>
I use a large Weller Soldering Gun when I can't find one of the
degaussing coils in the shop...
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
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| Re: Reviewing a cheap CRT degaussing wand [message #404132 is a reply to message #404116] |
Tue, 12 January 2021 20:48 |
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Originally posted by: Trevor Wilson
On 13/01/2021 7:48 am, Rayner Lucas wrote:
> 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
>
**I have always been an audio tech. I have always avoided TV work where
possible. However, back in the day, I would frequently perform a CRT
degauss, using my Han-D-Mag head demagnetiser. I found that it could
deal with any degaussing requirement.
https://www.ebay.com.au/itm/Tape-head-demagnetiser-demagneti zer-Han-D-Mag-220-240V-/271234117484
Geez, they're expensive nowadays. I still have mine.
--
Trevor Wilson
www.rageaudio.com.au
--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
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| Re: Reviewing a cheap CRT degaussing wand [message #404136 is a reply to message #404131] |
Wed, 13 January 2021 01:47 |
John Robertson
Messages: 17
Registered: July 2012
Karma: 0
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Junior Member |
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On 2021/01/12 4:56 p.m., Rayner Lucas wrote:
> In article <MPG.3a67ec6b38b8737098a116@news.east.earthlink.net>,
> rmowery28146@earthlink.net says...
>>
>> In article <fpmdnckH4tWUgWPCnZ2dnUU7-K2dnZ2d@giganews.com>,
>> spam@flippers.com says...
>>>
>>> I use a large Weller Soldering Gun when I can't find one of the
>>> degaussing coils in the shop...
>>
>> 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.
>
> 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
>
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 :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
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| Re: Reviewing a cheap CRT degaussing wand [message #404137 is a reply to message #404132] |
Wed, 13 January 2021 01:50 |
John Robertson
Messages: 17
Registered: July 2012
Karma: 0
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Junior Member |
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On 2021/01/12 5:48 p.m., Trevor Wilson wrote:
> On 13/01/2021 7:48 am, Rayner Lucas wrote:
>> 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
....
>> 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
>>
>
> **I have always been an audio tech. I have always avoided TV work where
> possible. However, back in the day, I would frequently perform a CRT
> degauss, using my Han-D-Mag head demagnetiser. I found that it could
> deal with any degaussing requirement.
>
> https://www.ebay.com.au/itm/Tape-head-demagnetiser-demagneti zer-Han-D-Mag-220-240V-/271234117484
>
>
> Geez, they're expensive nowadays. I still have mine.
>
A bit cheaper on this side of the pond:
https://www.atrtape.com/products/han-d-mag
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
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| Re: Reviewing a cheap CRT degaussing wand [message #404142 is a reply to message #404137] |
Wed, 13 January 2021 03:21 |
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Originally posted by: Trevor Wilson
On 13/01/2021 5:50 pm, John Robertson wrote:
> On 2021/01/12 5:48 p.m., Trevor Wilson wrote:
>> On 13/01/2021 7:48 am, Rayner Lucas wrote:
>>> 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
> ...
>>> 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
>>>
>>
>> **I have always been an audio tech. I have always avoided TV work
>> where possible. However, back in the day, I would frequently perform a
>> CRT degauss, using my Han-D-Mag head demagnetiser. I found that it
>> could deal with any degaussing requirement.
>>
>> https://www.ebay.com.au/itm/Tape-head-demagnetiser-demagneti zer-Han-D-Mag-220-240V-/271234117484
>>
>>
>> Geez, they're expensive nowadays. I still have mine.
>>
>
> A bit cheaper on this side of the pond:
>
> https://www.atrtape.com/products/han-d-mag
>
> John :-#)#
>
**That's more like it.
--
Trevor Wilson
www.rageaudio.com.au
--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
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| Re: Reviewing a cheap CRT degaussing wand [message #404314 is a reply to message #404116] |
Sun, 17 January 2021 13:26 |
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Originally posted by: Rob
Rayner Lucas <usenet202101@magic-cookie.co.ukNOSPAMPLEASE> wrote:
> 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.
Small wonder, as hardly anyone uses a CRT these days...
Normally when a CRT TV needs some form of repair, it will join its
fellows in the recycling bin.
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