Re: On RGB-to-component conversion

["js@cimmeri.com" <js@cimmeri.com>]

> 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.

** That monitor won't sync down that low via VGA port.


> 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.

** I obtained perfect stability using this method on a Samsung
SyncMaster 192MP.


> 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.

** I get the impression that the 9A60 might not work for 480i scan
rates.


> 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

** What a confused mess.  ;-)


> IIRC, the IIGS uses composite sync instead of separate horizontal & vertical
> sync.

** Correct... a separate composite synch...  "RGBs"


> 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.
> 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.

** They seem to be having difficulties, but only at the higher
resolutions.  They also keep noting that the circuit is only for
progressive scan.     The IIgs while being "480i" is actually not
interlaced, as far as I understand.. it's more like "200p".   Someone
please correct me if I am wrong.   Anyway, so that circuit might
actually work once the sync part was sorted out.

~ J