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Re: IIgs Analog Video Circuitry
- Subject: Re: IIgs Analog Video Circuitry
- From: MdntTrain <js@cimmeri.com>
- Date: Sat, 8 Oct 2011 17:52:40 -0700 (PDT)
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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
It's a sync inverter / adder. Sync going into H1 is digital, TTL,
thus not negative going. In H1, it's converted to negative going
(thus the two source voltages +5 and -5) and then combined with R-G-B.
- JS