Path: utzoo!mnetor!uunet!husc6!mailrus!nrl-cmf!ames!pacbell!att-ih!ihnp4!inuxc!iuvax!silver!commgrp
From: commgrp@silver.bacs.indiana.edu (BACS Data Communications Group)
Newsgroups: sci.electronics
Subject: Re: death of a friend
Message-ID: <1170@silver.bacs.indiana.edu>
Date: 14 Mar 88 14:31:23 GMT
Sender: commgrp@silver.bacs.indiana.edu
Lines: 40

>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