VGA Output Green???

[timdog82001]

I have a native installation of Gentoox Linux Home, v6.1, on an 80gb HDD, on my v1.4 xbox and cromwell bios, and this is what I am using now. For the record, I previously had linux installed for a short time non-natively in another hard drive along with other programs, and still experienced the exact same problem. I have a VGA cable I made using a tutorial over on xbox-scene, and it works perfectly. I used the lm1881n chip, and everything is definitely put together correctly. In fact, the cable works perfectly in the xbox dash and in games and in other programs. I get a perfect color, high resolution picture. For this stuff, I have switches 2 and 3 turned on (meaning, I have pins 11/12 and 13/14 connected). On my linux drive, booting with cromwell, having these two switches activated, everything boots and works perfectly...EXCEPT, everything is GREEN! I have full 720p widescreen resolution, and it looks great except for the color. in xbvset, i tried it selecting HDTV, and also using the X2VGA setting. If I have switches 1 and 3 activated (pins 9/10 and 13/14), the monitor turns itself off saying no signal. I'm guessing my problem would be fixed if I could get it to boot with 1 and 3.....But does anybody have ANY ideas of how to fix this??? Thanks in advance.

[Timmo]

I'm currently looking into the use of the HSYNC and VSYNC signals from between the GPU and the conextant chips to generate a more useful VGA signal. There is already a version of doing this on xbox linux using a buffer chip to generate 1.5V level for these signals however some monitor use TTL level for this signal (using a 0-5V signal instead of a 0-1.5V one). This should be pretty simple to do but I have not got round to installing it as I am waiting for a VGA connector to install my circuit. This will be used in a similar way to the buffer with the same pins of the AV connector linked for the VGA output but using two transistors for each line to attain the TTL levels. I am hoping that this should illiminate any problem with the green issue. Cromwell should pick up the VGA cable at boot stage running a resolution of 800x600 before the operating system kicks in and allows higher resolutions.

It may well be that some resistor values require tweaking but I think this is the way to go.
http://www.paultimmins.co.uk/images/pro ... s/SYNC.jpg
Using VSYNC as an example Q1 will switch at the 1.5V level, however it will invert the signal, Q4 should then revert the signal level and base it on 5V rather then 1.5V. After a quick look Q1 could be a BC182 and Q4 a BC212 which should allow the switching to be done in under 1us which when working on a resolution of 1024x768 should be sufficiently under the 17us ish signal rate to work. I'll update here as I try and use this circuit.