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May 17, 2005, 8:15 am
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I've just shifted my 80cm CRT from North-South facing to East-West, and
now have two faint but annoying colour blobs on the screen (small one
top right corner and big one middle left).
Turning the set on from cold the last few days has not made any difference.
Will an $80 degaussing wand from Jaycar fix this, or will it require an
expert to fiddle with the purity yoke magnets as well (in which case I
won't buy one)?
Speakers nearby? Large magnetic fields? Nearby electronics?
Do the spots go away when you turn the TV back where it was?
Do they move on the screen when you swivel it gradually back to where it was
Coil of electrical wire inside the wall (assuming it's near a wall)
generating a magnetic field?
Some form of bolt or stud in nearby wall causing disturbance?
Only the centre speaker but it is well shielded (B&W303) and in the same
place it was before. Moving the centre speaker makes no difference.
It weighs a tone - I'm not shifting it again in a hurry - and I can't
really swivel it in the (wooden) entertainment unit, but Ill give it a try.
Unfortunately I doubt it, it's backed against a (nearly full wall)
window with all wood construction and wooden Venetian blind.
While assembling some 3-way loudspeaker enclosures I made the mistake
of leaning a front panel, complete with speakers, against the front of
my 68cm CRT TV. The result was a large more or less permanent blob of
colour right in the middle of the screen.
Presumable I'd made a good job of magnetizing the shadow mask.
Take a 2 mH aircore inductor from the Bass-Midrange cross-over and
connect it to the secondary of a Scope soldering iron transformer (Can
anyone remember them?) via 1m of speaker cable. The ~4V resulted in
about 6.5A which the coil could take more or less permanently without
Sweeping the coil back and forward across the screen a few times did
the degausing for me.
Donald B Keogh
I recently had a science class full of year 3's. I handed out the bar
magnets and in less than 30 seconds one of the littil darlin's had
crossed the room and slammed his magnet against the computer monitor
like he knew damn well what it would do. I was livid!!
Thank God it had a degauss circuit, so it survived unscathed.
On Thu, 02 Jun 2005 05:12:11 GMT, Donald B Keogh
** Clearly the young person concerned appreciated the likely effect of a
magnetic field on the path of an electron travelling at 1/2 the speed of
light and was keen to give all present a simple demonstration ;-)
** I would have asked him/her to explain the visible results to the class
and then marked their answer out of 100.
** TVs would hardly be kid safe otherwise.
Thanks for the info.
I'm going away for a couple of weeks but will give this a go when I get
back. Jaycar seem to be out of stock of the degaussing wands. I have an
old Weller soldering iron transformer (24V I think), and will build
Just one thing, I thought you were supposed to wave the wand in slowly
increasing circles as you move away from the TV.
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