Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Old January 12th 21, 09:48 PM posted to rec.games.video.arcade,sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jan 2021
Posts: 3
Default Reviewing a cheap CRT degaussing wand

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

  #2   Report Post  
Old January 12th 21, 11:00 PM posted to rec.games.video.arcade,sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jul 2006
Posts: 873
Default Reviewing a cheap CRT degaussing wand

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."
  #3   Report Post  
Old January 12th 21, 11:27 PM posted to rec.games.video.arcade,sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jul 2006
Posts: 4,229
Default Reviewing a cheap CRT degaussing wand

In article ,
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.


  #5   Report Post  
Old January 13th 21, 02:48 AM posted to rec.games.video.arcade,sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jun 2009
Posts: 177
Default Reviewing a cheap CRT degaussing wand

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-hea...-/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



  #6   Report Post  
Old January 13th 21, 03:08 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Aug 2014
Posts: 1,177
Default Reviewing a cheap CRT degaussing wand

Trevor Wilson wrote:
================

**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-hea...-/271234117484

Geez, they're expensive nowadays. I still have mine.


** I once acquired a demagnetiser that, far as I could tell, was incapable of demagnetising anything.
Had no effect on tape heads or the tiniest screwdrivers. It was the Teac E1 as listed in your link.

So acting on a hunch, I made a coil of enamel wire ( about 15 turns) just big enough to slip over the head concerned and energised it from a small 6.3V tranny. The coil would get quite hot in about 30 seconds.

While energised, I popped it over the head and slowly removed it far away.

Totally worked on even the most magnetised heads.

Necessity is .......


...... Phil

  #7   Report Post  
Old January 13th 21, 05:47 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jul 2006
Posts: 367
Default 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

[to foil spammers, my address has been double rot-13 encoded]
  #9   Report Post  
Old January 13th 21, 07:50 AM posted to rec.games.video.arcade,sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jul 2006
Posts: 873
Default Reviewing a cheap CRT degaussing wand

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-hea...-/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."
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
After nutsack atheists complain, Marines reviewing whether to let Camp Pendleton cross stay. Let Recon handle the atheists once and for all. Steve B[_13_] Metalworking 1 November 23rd 11 08:00 PM
how large EMF field when Degaussing large CRT? Mike Sampieri Electronics 2 June 20th 05 10:20 PM
how large EMF field when Degaussing large CRT? Mike Sampieri Electronics Repair 1 June 20th 05 09:48 PM


All times are GMT +1. The time now is 07:57 PM.

Powered by vBulletin® Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Copyright 2004-2021 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"

 

Copyright © 2017