Commodore 1702 monitor and PC VGA card?
Raymond Carlsen
> Does anyone know if this is even possible? It seems such a waste to not
> be able to use a perfectly good monitor (and I'm on a tight budget). It
> SEEMS to me that such an adapter should be possible but I dunno...I can't
> find a wiring diagram for the 1702 cable.
Michael,
They are great monitors, but -only- work with NTSC video. VGA is RGB,
and runs at a much higher frequency (31.5KHz and up) as opposed to 15KHz
for video and CGA (what a 128 puts out in 80 column mode). If you really
need the 1702 cable pinout, email me. Hooked up to a video source like a
VCR (tuner), the 1702 produces a very nice picture... better than most TV
sets.
Ray Carlsen
CARLSEN ELECTRONICS... a leader in trailing-edge technology.
Michael Stamper
Does anyone know if this is even possible? It seems such a waste to not
be able to use a perfectly good monitor (and I'm on a tight budget). It
SEEMS to me that such an adapter should be possible but I dunno...I
can't find a wiring diagram for the 1702 cable.
Please help!
Michael Stamper
soli...@iquest.net
Raymond Carlsen
> > They are great monitors, but -only- work with NTSC video. VGA is RGB,
> > and runs at a much higher frequency (31.5KHz and up) as opposed to 15KHz
> With the right software, a VGA card can also output a PAL (NTSC?) signal.
Very early -CGA- cards did have an RCA connector on them to output a
sort-of NTSC signal, but a VGA card simply can't interface a video monitor
directly. To do that, you must match the frequencies needed (software can
do that if the card supports it), and you must somehow encode the RGB and
sync signals into NTSC or PAL composite video. There are "black boxes" out
there that do the conversion. I've seen them advertized for $150 and up,
but I don't know how well the "cheapies" do as far as picture quality,
especially if you want full motion video. If you're serious about
"downgrading" VGA to video, look up www.surplusdirect.com. They have those
little PC to TV boxes advertised all the time.
Toine de Greef
Raymond Carlsen (rr...@u.washington.edu) wrote:
> > Does anyone know if this is even possible? It seems such a waste to not
> > be able to use a perfectly good monitor (and I'm on a tight budget). It
> > SEEMS to me that such an adapter should be possible but I dunno...I can't
> > find a wiring diagram for the 1702 cable.
> Michael,
> They are great monitors, but -only- work with NTSC video. VGA is RGB,
> and runs at a much higher frequency (31.5KHz and up) as opposed to 15KHz
With the right software, a VGA card can also output a PAL (NTSC?) signal.
Toine.
--
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Mr. X
Toine de Greef <to...@stack.nl> wrote in article
<60udjk$q...@toad.stack.nl>...
> Raymond Carlsen (rr...@u.washington.edu) wrote:
> > > Does anyone know if this is even possible? It seems such a waste to
not
> > > be able to use a perfectly good monitor (and I'm on a tight budget).
It
> > > SEEMS to me that such an adapter should be possible but I dunno...I
can't
> > > find a wiring diagram for the 1702 cable.
>
> > Michael,
> > They are great monitors, but -only- work with NTSC video. VGA is
RGB,
> > and runs at a much higher frequency (31.5KHz and up) as opposed to
15KHz
>
> With the right software, a VGA card can also output a PAL (NTSC?) signal.
>
> Toine.
No, a 1702 supports "Composite" and "Split Y/C" which is like very early
SVHS. In one case all signals are encoded on one line, and in the other
the Y, which is the Luma aka Brightness, the B&W part of the signal is on
one line and the C, wich is the Chroma aka Colour is on the other line.
And it's all at 15KHz.
PC style VGA monitors are analog but they have 3 lines, Red, Blue and
Green, each amplitude encoded, pretty much being the signals for each of
the guns in your monitor. And it's all at 31KHz.
Now, a 1702 has no RGB inputs of any kind, and even if it did, the rest
of the electronics are not made to operate at 31KHz.
I consider it *extreemely* doubtful that normal VGA card could output a
15KHz signal, even if you had a composite encoder. VGAs were designed for
monitors in the 31KHz and up range, as are their monitors.
If you really want to use your 1702 with your PC, you'd need a PC card
that can output a TV signal that supports Composite out without software
support, so you can use it as your only monitor. Or, a stand alone VGA->TV
encoder that supports composite, or a VCR to route the RF to composite. In
any case, the hi-res modes on your PC will be very blury if they're even
supported. Pix would be OK, and most games, but word processing would be
hard. These devices were developed mostly for playing PC games on your TV.
Conclusion: Unless you're really cramped for space, or can get the
parts for free, it's not worth it. Look for a cheap SVGA monitor. Then
you can be on IRC and still play games on your 64 at the same time.... :)
CU
Marko Mäkelä
Sorry, this is going to be an off-topic article again.
>>>>> "X" == X <m...@spam.free.net> writes:
X> I consider it *extreemely* doubtful that normal VGA card could
X> output a 15KHz signal, even if you had a composite encoder.
Cards with programmable clock generators can do this without problems.
And if you use a high enough horizontal resolution, you should be able
to get 15kHz out of the original VGA card. I think that its lowest
clock was something like 25175 kHz, and 25175/15.625 = 1611. That
rounded to the nearest multiple of 8 pixels yields 1608. As you need
to leave some margin for the horizontal sync signals, you could get
something like 1200 pixels vertical resolution.
The guy who sold his fixed-frequency screen to me said that he had
configured XFree86 for use with his 1084 monitor (analog RGB input).
He got something like 700x550 interlaced resolution out of it.
Of course, if you are stuck to DOS and M$ products, you have to use
the "standard" video configurations. But the hardware really is quite
flexible.
Marko
--
Marko Mäkelä <Marko....@HUT.FI>, http://www.hut.fi/home/msmakela/
Helsinki University of Technology, dept. of Computer Science