Scott Alfter wrote:
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There's been some talk about ways to hook newer monitors to the IIGS
lately. Having just bought a new monitor with a bunch of different
inputs (a Samsung
SyncMaster 215TW), I tried plugging the VGA cable into the GS's RGB
output
through a Mac-to-VGA converter dongle. It was a long shot, so I
wasn't too
disappointed that it didn't work.
I then repeated the composite-to-component-Y-input test about which I
posted
earlier. That worked, and the image was a bit more stable than it was
on my
TV.
This gave me an excuse to start digging into what would be involved in
connecting a IIGS to a component input. There's an off-the-shelf option
that might work. The Audio Authority 9A60 (google for it) is popular
among
MythTV users who drive HD monitors with their computers. It's
anywhere from
$100 on up, though.
This is an "I can't be bothered to sell anything for less than $100"
price. ;-)
The schematic for the first solution below is exactly what is involved,
and it is quite trivial--component cost under $10 in quantities.
On the prowl for a cheaper solution, I ran across these pages:
http://archive.avsforum.com/avs-vb/history/topic/193919-1.html
http://www.keohi.com/keohihdtv/interfaces/diytranscoder.html
http://www.keohi.com/keohihdtv/interfaces/diytranscoder_johrhees.html
I took a look at the first of these, and it should work perfectly.
Scan rates and interlace are not a property of the signal conversion,
and so are irrelevant to this discussion. The video raster you see
will always be the one that the IIgs generates.
IIRC, the IIGS uses composite sync instead of separate horizontal &
vertical
sync. I'm guessing that the sync-combiner section (the 74HC00, the two
transistors, and related passives) can be deleted, or maybe replaced with
something much simpler. The rest is about what you'd figure it would be.
Correct--you don't need the sync combiner since you already have
composite sync.
The first link suggests some alternate component choices for the
opamps, and
it has some other info. It looks like between the three of them,
there's a
starting point for putting something together that'll work.
Only the ratios of the resistors are important, and are determined
both by the gain required of the opamps and by the (standard) RGB-to-
component matrixing.
Any number of video bandwidth opamps should be suitable--there are
bushels of them these days.