Re: IIgs Analog Video Circuitry

[MdntTrain <js@cimmeri.com>]

On Sep 30, 1:23 pm, Daniel Kruszyna <d...@krue.net> wrote:
> Kevin Dady <ke...@hackaday.com> wrote:
> > its probably some form of summer, you generally cant take a bunch of voltages
> > and simply wire them together and expect them to work (correctly), and yes if
> > its a epoxy blob sip IC chances are its custom, even if its not good luck
> > finding it unless its a scavenged / nos part...
>
> > Is yours broken?
>
> Fortunately no, my IIgses are all working fine. My main reason for asking is
> that I'd like to output to an AppleColor RGB monitor for a project I'm working
> on. I thought that copying the IIgs video output circuitry would be an easy way
> to do so.
>
> Another option I'm looking at is this chip:
>
> http://www.analog.com/en/audiovideo-products/video-encoders/adv7123/p...
>
> It looks like I'd still need to generate the composite sync separately though,
> since this chip only provides the rgb signals.
>
> -- Daniel

It's possible that the IIgs added sync to its colors just for
compatiblity with more monitors, because, according my Applecolor RGB
monitor manual, it syncs off the separate composite sync signal,
negative going, 3volts min. peak-to-peak into a 2200 ohm termination,
with the video lines of course going into 75 ohm termination.

In this case, you would not need to worry about exactly duplicating
the IIgs's output structure... just provide standard RGB+S.

- jS