14 Sep
2005
14 Sep
'05
11:30 p.m.
Can anyone recommend a book on the theory of operation
of RGB computer monitors. I imagine a book that
concentrates on monitors, as opposed to TV's in
general, is probably uncommon. In that event, a
recommendation for something general would be
appreciated, whether a past or present publication.
Purpose: the investigate the possibility of modifying
a recent multisync to sync down to TV frequencies. Not
interlaced necessarily. Just to use a modern monitor
with stuph that operates between CGA and VGA
frequencies. Much obliged.
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16 Sep
16 Sep
11:14 p.m.
Can anyone recommend a book on the theory of operation
of RGB computer monitors. I imagine a book that
concentrates on monitors, as opposed to TV's in
general, is probably uncommon. In that event, a
I've not found one....
Monitor circuitry is, not suprisingly, similar to TV circuitry, in fact
the older (fixed-scan rate) monitors were in some cases almost
indentical.
I would start by getting some good books on TV servicing. Unfortunately I
can't recomend any of thsoe either -- I started learning about TVs when
they were full of valves, and all my introductory books date from that time.
I have not found a good book which covers multi-sync monitors at all.
Some service manuals are available (either officially or not), but often
the theory-of-operation is conspicuous by its absence. You get a
schematic and setting-up info and little more.
recommendation for something general would be
appreciated, whether a past or present publication.
Purpose: the investigate the possibility of modifying
a recent multisync to sync down to TV frequencies. Not
interlaced necessarily. Just to use a modern monitor
with stuph that operates between CGA and VGA
frequencies. Much obliged.
Eeek! You've picked an 'interesting' project. Personally I think it would
be easier to find an old TV-rate monitor and repair it, even if you have
to wind replacement transformers yourself. But anyway...
I am sure you know that the horizontal output stage also supplies most of
the high voltages for the CRT. It is not at all obvious to me that you
will be able to drop the scan rate to TV rates and maintain all the
voltages at their correct value, and maintain the image width.
-tony
17 Sep
17 Sep
12:53 a.m.
Tony Duell wrote:
Sam Goldwasser's online repair FAQ is of course full of useful info,
including some of the theory:
http://repairfaq.ece.drexel.edu/sam/monfaq.htm
cheers
Jules
Can anyone
recommend a book on the theory of operation
of RGB computer monitors. I imagine a book that
concentrates on monitors, as opposed to TV's in
general, is probably uncommon. In that event, a
I've not found one....
Monitor circuitry is, not suprisingly, similar to TV circuitry, in fact
the older (fixed-scan rate) monitors were in some cases almost
indentical. 
2:06 a.m.
> recommendation for something general would be
> appreciated, whether a past or present publication.
> Purpose: the investigate the possibility of modifying
> a recent multisync to sync down to TV frequencies. Not
> interlaced necessarily. Just to use a modern monitor
> with stuph that operates between CGA and VGA
> frequencies. Much obliged.
I'll echo that I don't think it's practical to do this. Modern multisync CRT
monitors contain lots of circuitry to manage the various linearity and distortion problem
imposed by the need to vary sweep frequencies. The horizontal sweep components, in
particular, won't let you get much below 32 Khz or so.
I suppose one could use a TV-freqency video "frame grabber" on a PC to acquire
then display on a modern monitor, but that seems to be the long way around the job.
Far better to find an inexpensive broadcast receiver and hack into the video and sync
circuitry as needed. My first 64-column monitor (hooked to a modified SWTP TV Typewriter)
was an old tube-type Zenith monochrome portable TV (with an isolation transformer on the
mains supply, since this was a "hot chassis" model. Worked just fine until I
latched onto a Beehive Super Bee terminal.
Or cruise the junk shops for old monitors--there should still be a few wandering around
that have 15-18 KHz horizontal sweeps.
I think I even have an old Mitsubishi Diamond Scan monitor that will sync between TV and
EGA frequencies. I use it with an RGB demodulator and an East German VCR to view PAL VHS
tapes that friends from Europe send me.
Cheers,
Chuck
19 Sep
19 Sep
7:09 p.m.
Chuck Guzis wrote:
Why not just use a TV, if you're looking for TV-ish frame rates? I used
a TV with my old CGA card *years* ago. Now I use a VGA-to-RGB cable and
a suitably strange modeline to play back video on a TV.
Gordon.
>recommendation for something general would be
>appreciated, whether a past or present publication.
> Purpose: the investigate the possibility of modifying
>a recent multisync to sync down to TV frequencies. Not
>interlaced necessarily. Just to use a modern monitor
>with stuph that operates between CGA and VGA
>frequencies. Much obliged.
I'll echo that I don't think it's practical to do this. Modern multisync CRT
monitors contain lots of circuitry to manage the various linearity and distortion problem
imposed by the need to vary sweep frequencies. The horizontal sweep components, in
particular, won't let you get much below 32 Khz or so.
I suppose one could use a TV-freqency video "frame grabber" on a PC to acquire
then display on a modern monitor, but that seems to be the long way around the job.
20 Sep
20 Sep
1:42 a.m.
New subject: Scan doubling, was Re: looking for a book on monitor theory
I'll echo
that I don't think it's practical to do
this. Modern multisync CRT
monitors contain lots of
circuitry to manage the various linearity and
distortion problem imposed by the need to vary sweep
frequencies. The horizontal sweep components, in
particular, won't let you get much below 32 Khz or
so. I suppose one
could use a TV-freqency video "frame
grabber" on a PC to acquire then
display on a modern
monitor, but that seems to be the long way around
the job. 
9:41 p.m.
New subject: Scan doubling, was Re: looking for a book on monitor theory
On Mon, 19 Sep 2005, Chris M wrote:
I'm sure you have a better handle on this then I
do,
but they're built not to go below ~32khz these days,
because there's no reason to. The earlier multisyncs
went down to 15.75khz. I wasn't suggesting it wouldn't
be a sizeable job. Might not be practical, who knows.
It would just be nice to have a way of producing an
output from a vintage puter in the absence of anything
older, and larger (19"+).
Aren't there relatively inexpensive scan converters these days?
Iv'e used a few, input VGA output TV, nasty-looking chinese-made
boxes for $80 or so. Fancy ones do buffering and complex
conversions, but shouldn't be needed here. I too have a bias
towards home-brew but there's times when forking over cash solves
the problem instanter.
7:02 p.m.
Why not just use a TV, if you're looking for
TV-ish frame rates? I used
While most modern-ish UK and European TVs have RGB intputs on the SCART
socket, I am told that such a facility is rare on US TVs.
On the other hand, modifying an isolated-chassis TV to have RGB inputs is
probably a lot easier than modifying an SVGA monitor to do TV scan rates.
-tony
19 Sep
19 Sep
3:25 p.m.
On 9/14/05, Chris M <chrism3667 at yahoo.com> wrote:
Purpose: the investigate the possibility of modifying
a recent multisync to sync down to TV frequencies. Not
interlaced necessarily. Just to use a modern monitor
with stuph that operates between CGA and VGA
frequencies. Much obliged.
You best bet on this is to modify the input signal rather than the monitor
itself. The analog circuitry in modern monitors isn't all that hackable.
Devices that do signal conversion are called scan converters/line
doublers/flicker fixers. You can find video-VGA conversion boxes just about
anywhere. Also check for CGA-VGA converter boards (usually advertised as
being for arcade video games). If you really want to do it youself, you can
probably find a schematic online that will do the job. It takes some logic,
3 or 4 high speed ADCs (assuming you want color), some memory, and 3-DACs.
There are some chips that will do the whole job, but I don't know too much
about their capabilities and adaptable they are.
20 Sep
20 Sep
4:35 p.m.
On 9/19/05, Eric J Korpela <korpela at ssl.berkeley.edu> wrote:
If you really want to do it youself, you can probably
find a schematic
online that will do the job.
Here's one place with schematics. If you are doing monochrome or RGB to RGB
conversion you should be able to simplify somewhat.
http://www.epanorama.net/links/videocircuits.html#tvvga
Eric
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ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
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gordon＠gjcp.net -
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