Re: APPLE COLOR PLUS Display with Laser 128 (Apple IIc Clone) : Is it possible ?

[mjmahon@aol.com (Michael J. Mahon)]

Jose Carlos Lord Apple asked:

>> Sorry Jos�, the Apple Color Plus Display is a Macintosh monitor. It runs 
>> at a horizontal line frequency of 35 kilohertz. The Laser 128, like the 
>> IIgs, needs a monitor which can sync to 15kHz, the same frequency that 
>> TVs run at.
>> 
>> -- 
>> Roger Johnstone, Invercargill, New Zealand
>> 
>Humm, 15 kHz, that's means I can't use a CGA Mono Monitor with it. Am
>I right ?

No, CGA is 15.7 kHz horizontal sweep.  The issue is that CGA is
TTL, not analog, RGB.  Without an adapter, you won't be able
to couple the video, even though the monitor could sync to the
correct sweep rates.

> Is It possible to convert the CGA signal to composite signal
>? I verified that the DB9 plug on CGA monitor only needs:
>- Ground 
>- HSync
>- VSync

I think you mean could you convert your Laser's composite
video to TTL RGB for the CGA monitor.  This is not an easy
conversion, since it would be necessary to demodulate the
composite chroma signal (on a 3.58MHz subcarrier) and then
matrix it to obtain RGB, then threshold it to get discrete
TTL RGB colors that would be a poor approximation to the
analog composite colors that you desire.

Your best approach for displaying NTSC composite color
is an NTSC TV monitor.

>Thanks for your help and sorry by my "terrible" English !!

It's quite understandable.  ;-)
-michael

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