OBRIEN%OBRIEN@VENUS.YCC.YALE.EDU ("James A. O'Brien 432-4382", 203) (03/19/88)
For some time now, I've noticed that the screen of my Rainbow will do an
occasional flickering 'dance' for a while. There was a message posted some
time ago by Larry Campbell which suggested that the culprit was, in his
experience, usually the ribbon cable which connects the power supply to
the system board. I just installed a new cable, but guess what? It still
flickers! Now, I'm almost too scared to consider the next logical culprits
- something in the video system? Like many people, my Rainbow was paid
for using personal funds (as opposed to being a machine I use solely at
work) and we all know the huge repair/replacement price tags. Anyone have
a clue about what I can try next?
Jim O'Brien
Department of Chemical Engineering
Yale University
P.O.Box 2159 Yale Station
New Haven, CT 06520, U.S.A.
+1 203 432 4382
Return Addresses (both equivalent):
OBRIEN@YALEVMS BITnet
OBRIEN@VENUS.YCC.YALE.EDU internetmovshon@acf8.UUCP (Tony Movshon) (03/20/88)
Jim O'Brien worries about flicker on his Rainbow screen. I have
occasionally experienced a jitter which seems to be a pure video problem
within the VR201 monitor, and has nothing to do with the power supply
connector. If you feel venturesome, you can open the VR201 and make sure
that everything within is well-seated -- it's pretty shabbily made
inside and I wouldn't be at all surprised to find a bad contact of some
kind.
Once you have the monitor open, by the way, it often pays to adjust the
screen brightness, focus and geometry using the marked presets, because
these are often badly mis-adjusted. It's also possible that the jitter
(if it's the purely-horizontal character jitter that I have seen), comes
from a dirty preset pot, which you can tackle at the same time.
The usual cautions: don't mess around inside a video monitor unless you
have some idea how to deal with high-voltage electronics. But don't pay
DEC to work on your VR201, either -- I've never found a DEC service tech
willing to go inside the monitor; they just replace 'em. Comes from
being trained on 5-volt electronics, I guess.
Tony Movshon
Internet: movshon@nyu.edu
Usenet: movshon@cmcl2.uucp or {ihnp4|allegra}!cmcl2!xp!tony
US Mail: Department of Psychology, NYU
6 Washington Place, room 1083
New York, NY 10003
Phone: (212) 998-7880jto@santra.UUCP (Jari Tomminen) (03/26/88)
If the flickering is like vertical jumping or sudden shrinking and expanding of the picture in vertical direction - just the way my monitor did - maybe this info I got will help you... There might be "cold" solderings in the monitor electronics. Check and, if necessary, resolder: - all connectors - all big coils, especially streak transformer and the red one with some stuff under it - brightness and contrast controls - also, if necessary, change the 100ohm, 0.5W recistor near the edge of the card beside the red coil. I did most of the things mentioned above and, voila, all flickering and dancing ceased. Enjoy, Jari. -- | Jari Tomminen, Computing Centre | BOOT: | | Helsinki Univ. of Technology | What your friends give you because | | {anything}!mcvax!santra!jto | you spend too much time bragging | | jto@santra.hut.FI, jto@fingate.BITNET | about your computer skills. |
OBRIEN%OBRIEN@VENUS.YCC.YALE.EDU ("James A. O'Brien 432-4382", 203) (03/28/88)
Thanks to all who replied to my call for help on my Rainbow's flickering
screen, both directly and to the net. I performed a little open-monitor
surgery the other evening, and adjusted the trim pots inside the monitor.
That seems to have done the trick - at least, I've not seen any flickering
during the past few days. A word of advice if you do this (aside from the
obvious danger of screwing around with high-voltage devices!) - run all
of your graphics programs before you close up the patient again. I had
everything set beautifully the first time, or so I thought, until I closed
everything up, and tried to run a GSX-based graphics program. The horizontal
hold was crazy (although all of the other graphics and text stuff I own
worked fine!). [Can anyone comment on why GSX handles things differently?]
Anyway, thanks!
Jim O'Brien
Department of Chemical Engineering
Yale University
P.O.Box 2159 Yale Station
New Haven, CT 06520, U.S.A.
+1 203 432 4382
Return Addresses (both equivalent):
OBRIEN@YALEVMS BITnet
OBRIEN@VENUS.YCC.YALE.EDU internet