Re: Fw: Dodgy monitor

[Craig Andrews <nospam [at] fishbot.free-online.co.uk>]

> Forgive the technicalities... now we delve into the innards your monitor...
> 
> Changing picture width is due to poor EHT regulation in the monitor... try
> it again with the brightness control set to 'detent' (centre position) and
> contrast to max, these are the default factory settings for most monitors.
> This is a noticeable characteristic of most cheaper CRT monitors, and more
> likely to be a design flaw than an actual fault in your monitor. It is
> caused by the fact that the EHT supply (approx 26kV) is more heavily loaded
> when displaying a mainly white screen than a mainly black one (as it is
> producing a lot more light), and as the EHT supply is derived from the
> system that performs the horizontal scanning then a significant change in
> the picture brightness level can cause a noticeable change in the width of
> the picture. The monitors power supply _should_ be beefy enough to run the
> tube flat out without noticeable change in width but with an economy monitor
> this is often accepted as a reasonable trade-off for a slightly cheaper
> power supply.
> 
> --

Funnily enough, I did know this. I did spend some of my training years
repairing monitors and such, and learned quite a bit from it. Only thing
is, I have never come across it in a new monitor (mostly because this is
the first NEW monitor I have ever owned). I know IBM VGA monitors used
to do this, sometimes when not too old, and some early digital monitors.
I guess I presumed they must've found a way round it by now!!

I have adjusted the contrast and brightness (first resetting all factory
defaults), and the problem seems negligible (is that right?) unless the
screen is almost completely white, and is turning almost completely
black. So far, only Netscape has done this, so things should be OK.
Also, changing the refresh from 72Hz to 85Hz seems to have reduced it
quite a bit. One more modeline, then.

Cheers everyone who contributed. Seems to be working fine now.

Craig
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