MBPro starts but screen dead

Hi!

When I press the start button on my MBPro I hear fans, DVD, HDD rev up and power led behaves as it should, but that's it. I hear no startup chime and the screen doesn't activate at all. I have tried SMC reset, I have tried to start it with power adapter only (adapter is working, I use it on my other MB) and I have checked that the RAM is mounted correctly. I removed the hard drive and connected it to my other MB and it works correctly, so luckily I can do a back up of it. Do any of you have any suggestions what I could try next?

Sincerely

/Fredrik