Degausing

[Caliban]

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)?

 

[Mark H]

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
facing?

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?

 

[Caliban]

Mark H wrote:

Speakers nearby? Large magnetic fields? Nearby electronics?

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.

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
facing?

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.

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?

Unfortunately I doubt it, it's backed against a (nearly full wall)
window with all wood construction and wooden Venetian blind.

 

[Nathan L,]

Caliban wrote:

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)?

Judging from the odd tv manual i've read (haha) leaving the set
unplugged in its new location for so much as half an hour might set this
right.

 

[Donald B Keogh]

Hi Caliban,

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.

My solution:

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
overheating.

Sweeping the coil back and forward across the screen a few times did
the degausing for me.

Cheers,

Don Keogh
Donald B Keogh