Dell :: Inspiron 9300 Screen Swap With 9400

I'm trying to repair a 9300 with a radeon x300 video card in it - after the LCD panel died.

I've tried two panels to replace it, a WUXGA and a WXGA both from a 9400 - both panels are tested, and known to be absolutely working, as are the inverters.

In the 9300, the LCDs work, but the backlight doesn't come on, so they are effectively useless. I've tried them with all combinations of inverters, the ones specifically for those screens, then swapped around, and then changed for the original 9300 WUXGA inverter - nothing makes any difference, even though all parts are tested and working in a 9400.

The machine works fine with an external monitor, and in-a-sense works fine with the LCD panels - the output is working fine both ways, just not the backlight.
I've just never heard of a backlight problem on the card, only ever the inverter or backlight. The fact that the card was working fine before the old panel died also makes me doubt a problem there (and the old panel was an LCD problem, not a backlight problem).

Unfortunately, an LCD panel with no backlight at all is unusable, as it's almost impossible to see anything at all - much worse than a dim backlight. You have to hold it at the right angle, in the right lighting conditions, and squint

I've just tried flashing to the latest A05 system bios, and the latest ATI video bios from Dell, and that hasn't helped. Is there some good reason that 9400 panels aren't compatible with a 9300, or have I got a video card with dead backlight output?

The video card is the only thing I can think of, but it was working fine before the old panel died, and I've never heard of symptoms like this.

I don't have a working panel from a 9300 to test with, and can't afford to risk buying another panel, also replacement cards for the 9300 are like hens teeth.