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General Category => Amstrad CPC hardware => Topic started by: radu14m on 18:02, 24 September 13

Title: SCART cable - Green / White
Post by: radu14m on 18:02, 24 September 13
Is it possible to modify the SCART cable to get the only a green/white display on a normal color TV ?
I don't want to display all colors, just green&white like on GT65.


Title: Re: SCART cable - Green / White
Post by: ralferoo on 19:57, 24 September 13
Hmmm. I've never heard of anyone wanting to do this before, but you could probably send pin 6 of the CPC signal to the SCART green and tie SCART red and blue to ground.

So:
pin 6 of CPC -> pin 11 SCART (LUM)
pin 4 of CPC -> pin 20 SCART (SYNC)
pin 5 of CPC -> pins 5,7,9,13,15,14 SCART (GND)

That'll give you bright green for full intensity. If you actually want white, it gets more complicated. You can't just tie pin 6 to pins 7,11,15 as the TV will have a 75 ohm resistor on each, leading to an effective 25 ohm resistance and so the picture would be 3 times too bright. You'd then have to do something like a 220 ohm and 100 ohm resistor divider, 100 ohm to GND, 220 to LUM and the tap to pins 7,11,15.
Title: Re: SCART cable - Green / White
Post by: TFM on 20:01, 24 September 13
Quote from: radu14m on 18:02, 24 September 13
Is it possible to modify the SCART cable to get the only a green/white display on a normal color TV ?
I don't want to display all colors, just green&white like on GT65.




Cut off the wires for Red and Blue.
Title: Re: SCART cable - Green / White
Post by: gerald on 20:48, 24 September 13
Quote from: TFM on 20:01, 24 September 13
Cut off the wires for Red and Blue.
Are you serious ?
Title: Re: SCART cable - Green / White
Post by: gerald on 20:51, 24 September 13
GT64 uses CPC pin 6 only, which is a mix of RGB and SYNC.

For a monochome display on your TV,  you just need :
CPC pin 6 (LUM) to SCART pin 20 (Video in)
CPC pin 5 (GND) ro SCART pin 18 (Video in GND)

ANd then select the proper input on your TV (usually EXT or AV)

Title: Re: SCART cable - Green / White
Post by: Bryce on 20:55, 24 September 13
Quote from: radu14m on 18:02, 24 September 13
Is it possible to modify the SCART cable to get the only a green/white display on a normal color TV ?
I don't want to display all colors, just green&white like on GT65.

Not really. You could get a grey scale picture, but getting an acurate GT effect on a colour TV is difficult. It would need circuitry. You could connect the LUM signal to the Green pin on the SCART, but you would probably need a variable resistor to tune it and it would never look right in my opinion.

Bryce.
Title: Re: SCART cable - Green / White
Post by: radu14m on 12:25, 25 September 13
Thanks guys.
The ideea is to use my tv and get a Gt65 look :)
Title: Re: SCART cable - Green / White
Post by: Gryzor on 17:51, 29 September 13
Does the green monitor feature white, or is it just bright green?
Title: Re: SCART cable - Green / White
Post by: Bryce on 21:07, 29 September 13
It's all green, just the intensity varies, but the green isn't exactly the shade of green that the pure RGB green signal gives, so to produce the exact GT65 green you need to add a little Red and Blue to get it 100% right.

Bryce.
Title: Re: SCART cable - Green / White
Post by: Gryzor on 18:49, 30 September 13
What I thought... it didn't make sense.
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