Re: Monitor (was Re: Laptop question)

[Al Hudson <nospam [at] york.ac.uk>]

On Sun, 27 Feb 2000, Andrew Basterfield wrote:

> > I would dig further into that, then, if I were you. It sounds like you're
> > running the monitor close to the winds, it might be worth sitting down
> > with a piece of paper and going through the math of these modelines of
> > yours ;))
> 
> Virtually all monitors produced in the last 5 years have integrated
> protection in the chipset somewhere... if you try to run it outside it's
> frequency range it will usually drop into DPMS power management OFF state
> (usually the front panel LED will flash/change colour)

Given his screen screwed, I'm not convinced that either a) the circuitry
is good enough, or b) it works.. there are different types of circuits
they build into these things. Generally, the cheap ones will only prevent
over clocking, they won't check that the incoming mode is valid for that
monitor.

> Errr, no, not really. If there's a picture on the screen then generally the
> monitor is happy & healthy. In the back of the monitors handbook somewhere
> there might be a list of supported resolutions/horizontal/vertical
> frequencies.

I'm afraid I don't agree with that. If the picture's warping, it's not
happy. Tubes will take pretty much anything you throw at them, but the
oscillators and stuff tend to like being nice and steady - if they're
being thrown about all over the place, it's not going to do it any good. 

Also, the symptoms he described aren't just necessarily an overloading of
the l.o.t. - could be a problem with the trannies on the scan coils, for
example. When things go wrong with high-intensity pictures you can tell by
looking at it what the problem is: often, going dark is a sign of a
transistor giving up somewhere. Although, on a cheap monitor it could be
pretty much anything ;)) 

Cheers,

Alex.

P.S. Funny story for those who know how monitors work. A friend of mine
tried to attach speakers to his monitor, and got the cases screwed
together fine. Except, he needed a power supply (about 6VDC) to power the
measly amplifiers within the speakers. His clever idea was to source the
power from within the monitor, so with multimeter in hand he went round
prodding (note to readers: unless you know which bits of the board do
what, this is *not* a smart idea).. eventually, he found a 12V supply
somewhere (I think it fed the tuning circuitry, from what I remember), so
he turned off the telly and reached for the soldering iron. At some point,
he must have forgotton where exactly this pad he found was - he didn't
mark it - and somehow connected his potential divider to the line output
transformer (this is the EHT business mentioned in an earlier post - no,
not necessarily 26kV, *could* be as low as 14kV ;). Turned on the telly -
and there was much dancing of flame ;)) I'm pretty sure he blew the
monitor up too .... this is also the same guy who sent mains down a DMX
cable to a Pro Future Scan (flashy lights, for those who don't know ;)..
d'oh.


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