Re: C= PC1 graphics problem

From: Petri Andras (
Date: 2003-02-11 13:32:58

On Mon, 10 Feb 2003, Michael Huth wrote:

> Hello,
> I got a C= PC1 lately from a friend. It has a Motorola 6845 as CRT
> Controller. This controller
> seems to be capable of a 80x25 Textmode and CGA Graphics. The Board has a
> RGB Connector and a Composite-Video Connector and 4 DIP switches. The DIPs
> seem to have an influence on the Video Signal.
> The Problem is, I have only a TV or a BT878 based PC-TV card for Video
> Input. I tried the Video Out with the TV and couldn't get a Sync. Also my
> C128-RGB to Composite-Video Cable didn't worked.
> With one DIP combination I could get a barely visible Screen with my PC-TV
> Card. The PC1 itself seems to be ok (until it waits for a boot disk).
> So do I really need some CGA Monitor or is there any way to get it working
> with a usual TV (like the C128 RGB to Composite Video Cable). And what for
> is the Video-Out, if it does not works with a TV ?

Dear Michael,

the composite video output of the C= PC1 works ONLY if the DIP switches
are set to CGA mode (the CRTC can emulate both CGA and Hercules cards, but
it cannot produce a composite video signal in Hercules mode).

However, the composite video signal produced by a CGA card conforms to the
American NTSC standard (60 Hz vertical sync, 15735 Hz horizontal sync)
instead of the European PAL one (50 Hz vertical sync, 15625 Hz horizontal

Most European TVs can't process 60 Hz NTSC video signals properly (usually
they cannot even sync to 60 Hz), so it's no wonder that your TV doesn't
work with the PC1. The PC-TV card, however, may be able to cope with it
(it depends on the specific model's capabilities) if you can set it to
NTSC mode somehow.

Best wishes & good luck

Andras Petri, jr.

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