SCART cable - Green / White

Started by radu14m, 20:02, 24 September 13

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radu14m

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.



ralferoo

#1
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.

TFM

Quote from: radu14m on 20:02, 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.
TFM of FutureSoft
Also visit the CPC and Plus users favorite OS: FutureOS - The Revolution on CPC6128 and 6128Plus

gerald


gerald

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)


Bryce

#5
Quote from: radu14m on 20:02, 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.

radu14m

Thanks guys.
The ideea is to use my tv and get a Gt65 look :)

Gryzor

Does the green monitor feature white, or is it just bright green?

Bryce

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.

Gryzor

What I thought... it didn't make sense.

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