GT64/65 and composite signal

[FruityFrank]

Hello,

I'd like to 'abuse' my GT65 for another project and hook it to the TV-out of a raspberry pi 3.

Does anyone know if that is possible?

Many thanks!

[Bryce]

LUM and GND will give you some sort of picture, but I don't know the format or levels of the Pi TV-Out. I assume it's an Composite output? But, I've no idea what the picture would look like.

Bryce.

[robcfg]

Yes, the Pi has composite output.

The LUM signal is luminance plus composite sync, so feeding the composite output to that input pin on the monitor din plug (and ground, of course) should give you a picture.

I don't know if the encoded color information is going to create visible artifacts or get discarded.

Maybe the service manual of the monitor could be of help here:https://www.cpcwiki.eu/index.php/Service_Manuals

[FruityFrank]

Thanks for the help. Unfortunately I don't get it to work. I connected GND to pin5 and FBAS to pin 6 (the middle one). But the picture keeps rolling no matter how much I try with the v-sync dial on the GT65. Must be missing some sync signal I guess. i know the source is ok since it works perfectly on a regular tv.

[ZbyniuR]

Composite is two signals together, Luminance and Chroma. CPC Green monitor  needs only Lum. Years ago I had a similar need to connect Composite there and effect was terrible. I mean each line of pixels, depending on how many bright or dark pixels it had, moved to right or left sometimes by a few centimeters. My friend (better electronics than me) tried to make some sort of filter to separate Chroma and leave only Luminace. It partially worked, this sideways movement was down to just a few millimeters, and picture was good enough to recognize what it was, but still none vertical line was straight.
I suppose there are some filters on the internet, but maybe more expensive than buying another mono monitor with Composite In.