todd@uop.edu (Dr. Nethack) (03/13/88)
I have an old adds viewpoint I am using here, and the thing works fine except that the brightness is all the way down, and there is still background light on the screen. Can this be fixed? I don't mind hacking around on the boards. All I can think of doing is a tube brightener, but that is just impulsive. Are there some other parts I could fix or replace? Please help! Thanks ----------------------------------------------------------------------- + uop!todd@uunet.uu.net + + cogent!uop!todd@lll-winken.arpa + + {backbone}!ucbvax!ucdavis!uop!todd + -----------------------------------------------------------------------
commgrp@silver.bacs.indiana.edu (BACS Data Communications Group) (03/14/88)
>I have an old adds viewpoint I am using here, and the thing works >fine except that the brightness is all the way down, and there is >still background light on the screen. > >Can this be fixed? I don't mind hacking around on the boards. > >All I can think of doing is a tube brightener, but that is just impulsive. >Are there some other parts I could fix or replace? > >Please help! > >Thanks >----------------------- > uop!todd@uunet.uu.net Loss of contrast, in the absence of streaks, vertical lines, etc., usually indicates a worn-out "picture tube." If the phosphor is burned (brown spots in most-used area), then the CRT probably has zillions of hours' use and is almost certainly bad. A "tube brightener" is a transformer that raises the filament voltage, to get more cathode emission. That won't work in most CRT terminals because their filaments are DC-powered. Most monitors have internal brightness-control "trimpots." You may be able to improve the picture by tweaking the screwdriver adjustments on the monitor circuit-board. Electrolytic capacitors are a weak point in monitors. Look for discolored cases and bulged end-caps, especially on capacitors associated with power supplies taken from flyback-transformer windings. Also look for burned resistors and diodes associated with these capacitors. Replace any nonpolar electrolytics on general principle, using non-electrolytic types if possible. -- Frank Reid reid@gold.bacs.indiana.edu reid@iubacs.bitnet
tedk@ihuxv.ATT.COM (Kekatos) (03/15/88)
In article <1260@uop.edu> todd@uop.edu (Dr. Nethack) writes: >I have an old adds viewpoint I am using here, and the thing works >fine except that the brightness is all the way down, and there is >still background light on the screen. ---------------- Do you mean that you can see "rastor scan lines" on the screen? > >Can this be fixed? I don't mind hacking around on the boards. > Have to tried playing with the brightness and contrast controls? I think there is a video signal gain adjustment on the video board. Ted G. Kekatos backbone!ihnp4!ihuxv!tedk (312) 979-0804 AT&T Bell Laboratories, Indian Hill South, IX-1F-460 Naperville & Wheaton Roads - Naperville, Illinois. 60566 USA