Forcing AV channel on SCART TV

[Hamselv]

Hi there,

I have finally made a VGA-to-SCART cable to use with my ArcadeVGA card. It appears to be working fine (haven't actually gotten to the MAME part yet), but I seem to have one slight problem:

In order to force the AV channel to autoselect itself when it gets a signal from the AVGA, I have added a couple of wires to the SCART plug, which enables me to put 12V over pin 8 (and pin 14), as per the instructions on this site http://www.electronics2000.co.uk/data/pinout/scart.htm.

Now, without 12V on pin 8, I get a nice picture every 1-2 seconds, then black screen for a second and so on. When I connect my extra wires to 12V from a free PSU power plug (for HDD etc.), the picture stays on screen  

However, my TV seems to swap constantly between the two AV channels on the TV! The picture itself is rock-stable, but I get these annoying green OSD messages in the top left corner, saying "EXT 1" and "EXT 2" whenever the TV switches between the AV channels!

Does this sound familiar to anyone, and is there a way around it?

Btw... My TV is a 21" Phillips 21Gr2550/02b and I don't have the remote. Does anybody know how to get to the service mode of this thing, or how to adjust H/V hold manually?

Thanks!

[Hamselv]

Update (and shameless bump):

I just ran the AVres program, which creates .ini files for all the MAME roms, so that the ArcadeVGA will use the (most) correct resolution.

Result:   WOW!! This really does look absolutely fantastic! Better than I expected!  I get a little bit of color bleed occasionally, and I have a thin line at the top in all resolutions, which I am not sure if it can be fixed by adjusting H/V hold or not, but it is barely noticeable.

My main problem now is the actual screen size, which is a little bit too large to fit completely.

And of course, the d*mn green OSD message switching between "EXT1" and "EXT2" all the time! I tried adjusting the voltage over pin 8 with a pot, but without success....

I also tried searching for service manuals or service mode codes for my TV, but the only sites that carried manuals wanted more than