Re: IIgs to arcade monitor experiment

[MdntTrain <js@cimmeri.com>]

On Apr 22, 4:44 pm, Warren Ernst <wer...@gmail.com> wrote:
> On Apr 22, 1:59 pm, MdntTrain <j...@cimmeri.com> wrote:
>
>
>
>
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> > On Apr 22, 1:45 pm, Warren Ernst <wer...@gmail.com> wrote:
>
> > > On Apr 22, 10:13 am, MdntTrain <j...@cimmeri.com> wrote:
>
> > > > I'm my seemingly never-ending dallying with with IIgs video, I thought
> > > > I'd try interfacing my IIgs to an analog 15khz 19" RGB Electrohome
> > > > "Go7" arcade monitor I have here.. just to see how well it works (or
> > > > not).
>
> > > > I could use some insight on impedance matching and video signal level
> > > > from you resident masters of electron manipulation.  :-)
>
> > > > Here's the situation.
>
> > > > The IIgs video has these output specs:
> > > >   RGB:  1 Vpp @ 75 ohm impedance
> > > >   Sync:  4 Vpp @ 2k impedance
>
> > > > An arcade monitor (non VGA type) typically has these input specs:
> > > >   RGB: 4 Vpp @ 5k impedance
> > > >  Sync: 2 - 4 Vpp @ 35k impedance.
>
> > > > Video: these numbers don't look well matched, and I'm not sure what to
> > > > do about it yet.    If I connect the IIgs RGB directly to a higher
> > > > impedance than 75, the signal voltages are higher.. not as high as
> > > > 4V... but maybe enough for sufficient contrast.   However, does the
> > > > IIgs video signal get screwed up somehow if I don't load it with 75
> > > > ohms?
>
> > > > Sync: looks like a better situation.. as the voltages start out in the
> > > > right range.   I'm not sure but my guess here is that the 35k sync
> > > > input impedance won't be a problem for signal integrity ... as either
> > > > 2k or 35k are "high impedance" inputs.
>
> > > > Any thoughts are greatly appreciated as always.
>
> > > > JS
>
> > > Ask the guys on rec.games.video.arcade.collecting (RGVAC for short).
> > > They're a knowledgeable group.
>
> > > -Warr- Hide quoted text -
>
> > > - Show quoted text -
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> > Thank you, but I'd feel out of place posting there, Warren, because
> > this is more a general problem of interfacing between two video
> > signals of different levels and impedances, rather than anything
> > unique or specific to arcade games... although MAME/PC2JAMMA guys
> > might know about VGA to arcade monitor interfacing.. it seems they're
> > more hack oriented than well-versed in the video brilliance often on
> > display in this area (but hey, I've been wrong before).     IIgs RGB
> > and VGA video level/impedances have similar specs but might differ in
> > ways with which I'm not familiar.
>
> >   JS
>
> Listen, I own 7 vintage arcade games from the 80s, and most of them
> are in my living room right now. I maintain them myself, and regularly
> haunt RGVAC.
>
> Trust me. Your questions are appropriate for that newsgroup.
>
> -Warr- Hide quoted text -
>
> - Show quoted text -

Very cool.  Just bought a Zaxxon to restore.  I'm using its Go7 in
this IIgs experiment.

If I can't make sense of Michael's and Alex's wisdom, I'll try there
too.

 JS