"chaz_heritage.WGC1RX"@XEROX.COM (07/07/88)
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.
clf3678@ultb.UUCP (C.L. Freemesser) (06/18/89)
Howdy all, have a small problem. I picked up a monochrome monitor this week (used, $75), and need some help on fine tuning it. I did the screen enlargement, but there are two problems with this monitor. For reference, this one was built in July, 1985. 1) Screen jitter: Seems that the screen has a slight vertical jitter. What causes this, and is there any way I can fix it? It is somewhat annoying. 2) Screen "bent": The top right corner of the screen is "bent". There are some sort of magnets on the yoke (4 of them) that I assume control the deflection at the corners. How do I fix this problem? I did try moving them (loosened the screw and slid it around). The bend is not terribly bad, but it IS noticible. Thanks in advance for your QUICK reply. :^) Chris Freemesser, Rochester Institute of Technology | What I like : BITNET: %clf3678@RITVAX | 1) My Atari ST USENET: Just reply and hope it gets through | 2) My '77 Mercury "Another brilliant mind ruined by higher education" | 3) Coke Classic
swklassen@dahlia.waterloo.edu (Steven W. Klassen) (06/20/89)
In article <936@ultb.UUCP> clf3678@ultb.UUCP (C.L. Freemesser (709ITP)) writes: > >1) Screen jitter: Seems that the screen has a slight vertical jitter. > What causes this, and is there any way I can fix it? It is somewhat > annoying. > >2) Screen "bent": The top right corner of the screen is "bent". There > are some sort of magnets on the yoke (4 of them) that I assume > control the deflection at the corners. How do I fix this problem? > I did try moving them (loosened the screw and slid it around). The > bend is not terribly bad, but it IS noticible. > I had problems like this once with my monitor. It worked fine for about four months and then I had to move. The move required that I set up my computer in rather cramped quarters hence things were shoved together rather closely. I noticed that my screen tended to jitter. I also noticed that my power bar was placed right next to my monitor. When I moved the power bar away the jitter stopped. Similarly I once (very foolishly) placed a car stereo speaker, magnet down, on top of my colour TV for a few minutes (while searching for something in my junk box). This did all sorts of weird and wonderful things to the TV display and it remained distorted for about 3-4 minutes after removing the magnet! The moral of this (true) story is this: Check around your monitor. Remove anything which has either a magnet of any significance or any large amount of electricity moving through it (ie. power bars). Steven W. Klassen Computer Science Major University of Waterloo
ftw@masscomp.UUCP (Farrell Woods) (07/22/89)
Two folks have mono monitor problems, so I'll address both here.
To the fellow who has a linearity problem (the characters at the top of
of the screen get tall, etc.): Go to Radio Shack and get yourself a can of
"freeze mist". Also, arm yourself with a handheld hair dryer. With the
monitor running, and the back off, use the hair dryer to heat the innards
some. This should cause the problem to appear more quickly than it would
otherwise. Then, take the freeze mist and carefully zap components in the
vertical circuitry. Observe the picture while you do this. When the picture
snaps back to "normal", you have your faulty component.
To the fellow with the jitter and bends: The jitter might be fixed by
adjusting the "vertical hold" pot. I don't recall its location; it's been
a while since I've had my monitor apart. For the bends, it's probably caused
by a little too much enthusiasim when the previous owner stretched the picture.
You might try backing off on some of those adjustments. The rings you see
on the back of the yoke are for centering the picture on the face of the tube.
--
Farrell T. Woods Voice: (508) 392-2471
Concurrent Computer Corporation Domain: ftw@masscomp.com
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