R40 Video problem

[ohreallyriley]

I have the following R40: 2722-6yu Original description: P M 1.3GHz, Not installed(RAM, HDD), 15 SXGA+(1400x1050) TFT LCD, 32MB ATI Radeon 7500, Open bay, Wireless upgradeable, Modem(CDC), Ethernet(LOM), Secure Chip(TCPA), IEEE 1394, 8 cell battery, No preload

There is no video on the lcd. The external video works fine. The LCD shows a solid light gray color after booting. The backlight appears to be working. There is no redish tint etc. When using the F7 key to toggle between the external monitor and the lcd, the lcd will go totally black when the toggle is toward the external monitor. The same occurs when the sleep mode button is pushed.

I have replaced the lcd, power inverter and the lcd wiring harness and get the same results as noted above. I have mixed the original parts and new parts and still the same result.

After significant frustration, I took the unit to an "Authorized IBM Repair" facility. The tried all of the same things that I did and got the same result. They said it was probably a problem with the on board video card and I should replace the motherboard.

Does anyone have any suggestions before I look for compatible motherboard on Ebay.

Thank you in advance for any thoughts.

[Terrahawk]

The problem could be in the part that drives the LCD, the TMDS or whatever it's called. I'm not sure if it's integrated into the Radeon chip. Never had a look myself...

It's difficult to imagine how that would have happened though.

Forget it - my rambling thoughts lead also to the "replacement motherboard" conclusion.