[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:
http://web.archive.org/web/20070402195239/http://www.tkk.fi/Misc/Electronics/circuits/vga2tv/vgatv_troubleshoot.html
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
S-Video
d. give up and buy a new TV
e. something else?
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