Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ucbvax!XEROX.COM!"chaz_heritage.WGC1RX"
From: "chaz_heritage.WGC1RX"@XEROX.COM
Newsgroups: comp.sys.atari.st
Subject: Mono monitor problems
Message-ID: <880707-024028-1553@Xerox>
Date: 7 Jul 88 09:39:50 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 48

In his 23 Jun 88 05:24:11 GMT John Joubert writes:

>My monochrome monitor shakes also.  A friend of mine has one and it
shakes and has a strange kind of tilt to it also.  Anyone know of a 
good remedy?<

Round the back of the monitor are three tweakers, called VHOLD, VSIZE and
HPHASE. VHOLD controls the stability of the picture; if it is misadjusted then
occasional twitches or picture rolls may occur. Tweak this until the picture
rolls continuously, then tweak it back. The picture will stabilise, and, as you
tweak VHOLD further, start to roll again. The midpoint between the positions at
which rolling starts is a reasonable optimum.

VSIZE varies the vertical size to allow circularity to be set up; HPHASE varies
the horizontal position of the picture on the screen. Display a perfect circle
and adjust VSIZE until its X and Y diameters, measured on the screen, are
identical. Adjust HPHASE for optimum centering of the image on the screen.

If, having done this, the picture still shakes then it may be the result
(particularly in old monitors) of contamination of the tracks of the tweakers.
Careful application of a suitable cleaning spray (I could recommend some, but
you probably can't get them Over There - ask for 'switch cleaner' or 'computer
solvent / lubricant aerosol', etc.) may clear this fault. Working the control to
and fro while injecting the cleaner (from inside the panel) seems to work best.
NEVER DO THIS WITH THE MONITOR SWITCHED ON.

Failing that, the fault is probably due to a capacitor being on the point of
failing somewhere in the tube drive circuit. This would require service center
repair.

I assume that by 'tilt' is meant tilt of the image on the screen, rather than
mechanical tilt. The former may be adjustable by an internal tweaker or it may
be set by the alignment of the magnetic yokes and / or compensating coils on the
tube neck. It is often quite easy to adjust these, but please get the Atari
service manual for the monitor and follow its instructions TO THE LETTER if
you're gonna do this. If you fry yourself on the HT don't blame me.

Oh yeah, and if you DO get a copy of the service documentation I'd really love a
copy of it...... my mono monitor's only a couple of months old, so these
'internal' suggestions are generic to mono monitors in general. I've not taken
mine to bits yet.

Regards,

Chaz
(Everyone's PAL)

Disclaimer: I never told anyone to do anything. Neither did my employer. All
technical comments are strictly of academic or theoretical interest only.