[Coco] Help with RGB cable

[coco at yourdvd.net]

The pinout for the Apple II GS monitor is:
  1     Red video return
  2     Red video
  3     Composite sync
  4     --
  5     Green video
  6     Green video return
  7     --
  8     --
  9     Blue video
 10     --
 11     --
 12     --
 13     Blue video return
 14     --
 15     --
Shell   Shield ground

However, I believe Marcus mentioned that his had been retrofitted with a
commodore style DIN connector in place of the original Apple connector.
One other item of note: The Horizontal Sync of the Apple II GS is
15.734kHz on the 60Hz model and 15.696kHz on the 50Hz model, whilst the
CoCo outputs 15.75Khz, so the sync will be slightly off. As you
mentioned, a caveat of the composite sync generator is the need to
supply +5v. Most people take it from the joystick port, and this might
affect joystick resolution slightly. An alternative  might be to
piggyback a 74LS02 onto an existing chip in the CoCo 3. Using all
available gates in the 74LS02, you could then have available -csync,
+csync, -hsync, -vsync in addition to vsync and hsync that appears on
the connector at the bottom of the CoCo. You could install a 4-pin
header somewhere on the coco's case for these extra sync signals. -rob

> -------- Original Message --------
> Subject: Re: [Coco] Help with RGB cable
> From: Torsten Dittel <Torsten at Dittel.info>
> Date: Mon, March 26, 2007 3:43 pm
> To: coco at maltedmedia.com
> 
> Marcus Vinicius Garrett Chiado schrieb:
> 
> > Thank you very much, Rob. I recently bought a *real* 1084S (a D-II
> > model) and will try to use my actual cable with it for it has
> > composite sync already. As soon as I pick the monitor up, I will let
> > you know.
> 
> Marcus,
> the pinout on coco3.com is correct. I don't know this Apple monitor, but 
> like the 1084S it seems to need R, G, B signals plus a signal called 
> "Composite Sync". The CoCo3 already outputs R, G, B. For the missing 
> "Composite Sync" there are two choices now: You mix it from H & V 
> (horizontal and vertical sync) with the circuit described in an earlier 
> posting. Or: you use a so called "Sync Stripper" to generate it from the 
> CoCo's Composite *Video* out (another one-IC circuit). Disadvantage of 
> both solutions: You need a 5V power e.g. from another port of the CoCo 
> (joystick). Now the good news concerning at least the 1084S (no idea 
> about the Apple): The Composite *Sync* input already seems to have a 
> Sync Stripper circuit (which filters out the video information from the 
> signal). That means with a special Y-cable (1084S: D-SUB9, CoCo3: Cinch 
> and 9-pin header connector) you can use the 1084S in its RGB mode. Of 
> course you could just use its Composite Video mode (with just one Cinch 
> Coax video cable) but then the picture (and color!) quality is 
> significantly worse. Any questions: feel free to ask.
> 
> Regards,
> Torsten
> 
> 
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