Re: IIgs Analog Video Circuitry

[MdntTrain <js@cimmeri.com>]

On Sep 27, 8:08 pm, Daniel Kruszyna <d...@krue.net> wrote:
> In the IIgs, there is a component in the RGB output section which takes the R,
> G, B, and COMP/SYNC signals from the VGC and produces the signals at the
> monitor port. It is a single in-line component that is usually yellowish brown,
> but sometimes green in color. It has many little bumps in the package which
> suggest that it contains multiple discrete components integrated as a
> submodule. It is labeled H1 on the ROM 3 motherboard. Does anyone know what
> this part is?  Is it a custom Apple part or off the shelf? Is there a datasheet
> or schematic available?
>
> -- Daniel

I don't have my schematic handy, but two types of chips (post the VGC)
contribute to the rear port signals: there is the RGB-> NTSC converter
chip around there (I believe it's the MC1377 or similar), and then
there's the video D->A converters (DACs).  I'm not sure whether the
DACs are off shelf.

- jS