'Ken Moiarty' wrote, in part:
| My 19" Viewsonic A90's vertical refresh rate peaks out@ 100 Hz for a
| resolution of 1024 x 728. For stereo 3-D video viewing purposes, I need
it
| to display at this resolution at a bare minimum vertical refresh rate of
| approximately 120 Hz (though preferabley when I get another monitor, at
| about 170 Hz).
..
| Is there any way to over-ride the monitor's built in refresh rate
limitations
| (e.g. by tweaking some knobs at the back, or even inside, or by making
| simple modifications to a component(s) -only of course with the guidance
| andasistance of a licensed monitor technician due to obvious safety
| reasons)?
_____

Your question posted is 'Can one "overclock a CRT monitor's video input
bandwidth?' with the qualification of 'Need slightly higher refresh rate
than by existing CRT allows...'.

First, changing the VERTICAL refresh rate changes the HORIZONTAL rate. The
horizontal rate for 1024 X 728 at 100 Hz vertical refresh is just a bit more
than 728 X 100 = 72,800 Hz; the horizontal rate for 1024 X 728 at 120 Hz
vertical refresh is just a bit more than 728 X 120 = 87,360. The real
limiting factor is the horizontal rate, it is a high power circuit that
drives magnetic coils to sweep the electron beam from side to side. The
same circuit also develops the high voltage (15,000 to 20,000 volts) power
to accelerate the electrons toward the screen.

So it is not just the frequency response of the video amplifiers, which,
except for the final driver stages, run on milliwatts. It is a question of
the horizontal sweep circuits that account for 90% of the power used by a
CRT monitor. It is not a question of cooling, it is not like overclocking a
CPU or display adapter - it is more like trying to drive a Trabant at
autobahn speeds.

You might try 1280 X 720 at 120 Hz; 720 X 120 = 86,400 Hz horizontal sweep
rate, a bit lower than 1024 X 120 Hz. I tried this setting on my Viewsonic
A95f 19" monitor (I had to uncheck the 'Hide modes this monitor cannot
display' box on the 'Monitor' Tab reached clicking on the 'Advanced' button
on the display properties sheet. It works at 1280 X 720 at 120 Hz, though
the screen needs quite a bit of adjustment and the images are not as good as
on the same monitor at 1600 X 1200 at 85 Hz.

You can also run the display card/monitor at a lower vertical resolution say
960 X 600 at 120 Hz; 600 X 120 Hz = 72,000 or 1088 X 612 at 120 Hz; 612 X
120 = 73,440. Both of these resolutions have lower horizontal refresh rates
at 120 Hz than 1024 X 768 at 100 Hz. (Uncheck the box 'Hide modes this
monitor cannot display.

My Viewsonic is protected from unreasonable horizontal rates - at a setting
of 1024 X 768 at 120 Hz no image displays until after the 15 second time out
and the display adapter reverts to the previous good resolution and vertical
refresh rate. I assume your model is also, so give it a try, and let us
know the results.

Phil Weldon


"Ken Moiarty" wrote in message
...
| My 19" Viewsonic A90's vertical refresh rate peaks out@ 100 Hz for a
| resolution of 1024 x 728. For stereo 3-D video viewing purposes, I need
it
| to display at this resolution at a bare minimum vertical refresh rate of
| approximately 120 Hz (though preferabley when I get another monitor, at
| about 170 Hz). I could go out and buy another 19" monitor which purports
to
| be able to achieve the former for only about $250 (CAD) right now; in
which
| case the current CRT monitor will be gently laid to rest. So since it no
| longer matters what happens to my present CRT monitor since I'm going to
| replace it anyway, can I ask: Is there any way to over-ride the monitor's
| built in refresh rate limitations (e.g. by tweaking some knobs at the
back,
| or even inside, or by making simple modifications to a component(s) -only
of
| course with the guidance and asistance of a licensed monitor technician
due
| to obvious safety reasons)? Aside from the risk of electrocution to those
| who'd be foolhardy enough to attempt such an undertaking on their own
| without the proper training and qualifications to go inside a monitor, is
| it in any way technically feasible, given the right personnel, and done
| cautiously and gradually (much like a CPU overclocker takes a high risk
| gamble with the investment in his PC) to raise the monitor's refresh rate
a
| little beyond factory default and (say, if given extra cooling) be able to
| keep it there indefinitely?
|
| Sorry if my words above haven't come out quite right. It's late and I'm a
| little punchy at the moment.
|
| TIA,
| Ken
|
|