Monitor deflection magnets; what to do when one falls out & breaks? - test-drb@ccmp.vtda.org

15 Jul 2004

these are indeed magnets and were usually the dirt cheap variety. They were set in place
at the factory to "trim" the beam to overcome mechanical deviations in the gun
and deflection assemblies internal to the crt. They were not all that powerful. The best
source of replacement would be another old monitor that you can take the magnets out of. 

best regards, Steve Thatcher

-----Original Message-----
From: Brad Parker &lt;brad(a)heeltoe.com&gt;
Sent: Jul 15, 2004 11:54 AM
To: "General Discussion: On-Topic and Off-Topic Posts"
&lt;cctalk(a)classiccmp.org&gt;
Subject: Re: Monitor deflection magnets;	what to do when one falls out & breaks? 

Paul Koning wrote:
...

It's probably not a magnet, but rather a ferrite core.  You'd know the
difference putting the pieces together -- if you feel no attraction or
repulsion, it's not a permanent magnet. 
Interesting.  The pieces do attract.

Are ferrite cores magnetic?

(I would think a ferrite core would have wires wrapped around it)

These magnets are not connected to the wired internal yoke assembly -
they are glued to a "collar" which is close to the back of the tube.
The collar is round but the magnets are glued to make a square - I
assume this helps make the image square.  (or not :-)

The magnets on the two sides are symmetric as are the top and bottom.
Both top and sides have two "tube magnets" but ared spaced slightly
differently.  The sides have two magnets side by side with no gap.
The top and bottom have two magnets side by side with a a 1/4" gap.

I can see where the glue was holding the magnet.  That's where I put it
back.

I assume the poles should be aligned, i.e. the poles of the two magnets should
be the same, producing a larger overall field (I presume)

...
 As for the problem, I wonder if the issue is that the
core is in the
wrong spot.  It's part of the deflection magnetics assembly, and if
it's misplaced then you'd certainly get problems like you describe.
Take a look at the corresponding piece at the bottom of the yoke.  I
would expect things to be symmetric.  The fact that the thing fell out
suggests that it may have been out of position, and when you pushed it
back in you may not have gotten it back where it actually belongs. 
Well, it fell out onto the floor when I took the enclosure off :-)

-brad