[mythtv-users] Troubleshooting a VGA-SCART converter

Andrew Cranwell andrew.cranwell at gmail.com
Sun Oct 2 14:20:06 UTC 2011

Trying to not spend money on a new TV, I thought I'd try VGA-SCART.

Per http://www.mythtv.org/wiki/RGB_Scart and 
http://www.nexusuk.org/projects/vga2scart/ I've been trying to connect a 
new system (so far running from a livecd) with an NVIDIA GT520 card to 
an old CRT via the sync-converter circuit described, without much success.

I suspect the first problem is that the scan frequencies are simply too 
high - X doesn't seem to accept the 15.6kHz modelines (from 
http://www.mythtv.org/wiki/Modeline_Database) but will use the 31kHz 
non-interlaced modes - hopefully this will actually work as the TV can 
supposedly take 100Hz progressive input.

RGB is selectable as an A/V mode (though I did try the secondary select 
circuit at 
http://www.nexusuk.org/projects/vga2scart/voltage_from_vsync/view), and 
I've at least got RGB wired through correctly, but sync is eluding me 
(the image is blocky and madly scrolling everywhere).

Has anyone got some suggestions on what I should be looking for to test 
this? I'm reading through the following for advice:


I'm also trying to get hold of a CRO to test what's going on, but I'd 
like some advice on what to do - should I

a. persist with/modify the circuit (e.g. to sync-on-green?)
b. buy a VGA-composite converter
c. buy a suitable NVIDIA card (e.g. 8600GT) & use either VGA/SCART or 
d. give up and buy a new TV
e. something else?

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