Farmer Giles writes:

Terry wrote:
wrote in message
oups.com...
I've got a rare old vector arcade monitor from a "Warrior" arcade game
that came out in 1979. Everything works except that the picture is way
off center. To the point that about half of it is off-screen. I've
adjusted the horizontal and vertical controls as far as they go. So
I'm thinking I need to adjust the yoke. But I've never done that
before. I tried loosening the screw and I can rotate it which rotates
the picture. But I don't know how to move it to a different angle to
get the picture back in the middle. It's an old b&w monitor so I don't
have to worry about color convergience or anything like that. Can
someone give a novice a clue on how to go about this? Thanks!

John

John: There may be, as with old B&W TV sets a couple of usually
black cardboard looking circular pieces with tabs often mounted on
and comprising part of the back of the yoke. Those could be rotated
(gosh how rusty I am on this!) to magnetically centre the whole
raster (picture)? Try that? I guess the 'black things' were somehow
magnetic and steered the electron beam?
There used to also be an 'Ion trap' that had to also adjusted; if it
was way off the picture would show on the screen at all! IIRC the
trap was to steer the electron beam/s back towards the screen to
avoid ion burn? because the tube gun was manufactured not exactly
pointing at the screen. The ion trap looked like a springy open
metal clip around the tube neck and contained a small magnet about
half the size of postage stamp. Maybe that's missing? If so try a
smallish magnet to see if affects the problem.
But stand to be corrected on any of this by those more
knowledgeable. Terry

Ion traps were a good deal earlier than 1979. You are correct about
the tabs at the back of the yolk though - I think they were called
'shuffle magnets' or something like that(but my memory might be no
better than yours here) - and they might well be the cause of the
problem. Turning them independently of each other should centralise
the raster -
loosening and turning the yoke itself will only move the scan in the
horizontal plane (but make sure the yoke hasn't come loose and moved
away from the CRT).
All this assumes that it is a monochrome monitor.

Those never had enough range to cause what has been described, unless
perhaps deliberately totally messed up by someone before him.

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