DVI to HDMI video out

[bif]

Howdy folks,
I am currently in the middle of a project involving sending the video out from my PowerMac G4 MDD to my Sony HD TV. I have the OEM video card with ADC, DVI and VGA outputs connected to the TV via a DVI to HDMI cable. I also have an Apple 20 ADC display hooked up to the ADC port on the card while configuring and testing the set up. However, although everything works so long as the ADC display is connected, once I shut down and try to boot with the ADC display disconnected, the TV only shows a black screen. Is there some obviously obscure setting I am overlooking. I set the TV as the primary display, or display 0 in the system preferences before disconnecting the ADC display. Also made sure that the TV was set to an appropriate resolution. In Display Preferences the system software even sees the TV as "SONY TV" which gives me some encouragement. I have even tried using an old Sony multiscan monitor connected to VGA out and everything behaves the same as with the Apple ADC monitor connected.
Any ideas are welcome, and if anyone has already done this your lessons learned would be greatly appreciated.
Thanks in advance.

[Damien]

Grab a VGA to mac monitor adapter and connect it to the VGA port
or an ADC to DVI adapter to the adc port Then your Mac will think it has a screen there when it actually doesn't... used to have to do this all the time when booting headless or using the TV out on the old ATI cards

[bif]

I am posting just in case someone else tries this. I tried the VGA adapter with no monitor attached with no luck. I do not have an ADC to DVI or ADC to VGA adapter to try, they retail for 60-90 $, so I am not going to go that route. I have space in my entertainment center to stow the 17 inch ADC display and will set up the rig with it attached, hiding it most of the time behind a door. This will have to do, for me, and is not a bad compromise as I find it much easier to read the ADC display when fumbling with preferences and moving files.
As a side note, the quality of the playback from the computer DVD drive to the SONY TV via the DVI to HDMI cable is phenomenal. It is truly HD and better than the Sony DVD player, even using the component video cables. Strangely, the Apple DVD player software does a more consistent job delivering the correct screen resolution and aspect ratio than the DVD player did, allowing the subtitles to be visible on screen. Using the sony player the subtitles would sometimes be displayed out side the picture area and when the screen was zoomed they could not be seen. Zooming the screen was the only way to fill the picture tube when viewing in some wide screen aspects. I admit that some of this is my own lack of knowledge concerning the set up of my TV and the different type of wide screen DVDs, but so far, I am happy with this arrangement.
Thank you for your help.