black screen on boot (DVI) - Radeon 9550/9600/X1050 Series - Lubuntu 13.04

I get no signal after boot, yet when I hit the reset button the boot screen shows. What could be the problem?

thanks

monitor: lg flatron W2246T

ps: this is no duplicate as I get no black screen when I hit the reset button...

xrandr output

Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 4096 x 4096 VGA-0 disconnected (normal left inverted right x axis y axis) DVI-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm 1920x1080 60.0*+ 1680x1050 60.0
1280x1024 75.0 60.0
1152x864 75.0
1024x768 75.1 60.0
800x600 75.0 60.3
640x480 75.0 60.0
720x400 70.1
S-video disconnected (normal left inverted right x axis y axis)

8

1 Answer

Older video cards may fail to produce a good quality high resolution image on DVI. Most likely because of frequency instability (?). Default modeline for 1920x1080 results in a very high frequency that RAMDAC (?) on your video card fails to operate at.

You can try to reduce blanking time (RBT) and as a result lower frequency. You have to add new modelines with xranrd as described here. Instead of using cvt or gft, I suggest to use umc. The reason for this is that it can calculate modeline for lower refresh rate with --rbt, e.g. my monitor supports as low as 49.9 Hz refresh rate. cvt would insist on multiples of 60Hz.

Note on comment reply about LVDS... according to your output you should use DVI-0 when adding and setting new modelines.

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