iMac 24" Intel - boots up but no monitor (remains black)

[Skally]

I have one of the older intel core 2 duo white 24" iMacs. Have had no problems with it but a few days ago I left it to go to sleep for a few hours and now have no monitor. It comes on, power light glows, makes the coming on noise, whirs and clicks and if I plug my iPhone into it, it starts charging and even tethers but the screen remains completely black.

It may not be relevant but I downloaded and installed Lion a few months ago. Since then it has done one or two odd things like saying its not tethered when it is and twice I've done a disc and permission check with alarming results. It have repaired them. I know there are a few issues regarding Lion but it may be coincidence.

I have removed and cleaned the memory cards. Can anyone tell me how I can check if this is a software or hardware problem. I'm in Spain and not very confident about how easy it will be to get it repaired by Apple.

Any suggestions would be welcome.

 

[Skally]

Conact a monitor to an iMac

600+ people have viewed my post but clearly no one has any suggestions. If I attach another monitor to it I should be able to work out if it's the monitor or the software - or will I? It has a monitor socket but it's a type I've never seen before. What can I plug into it? Have an old G4 Mac screen and a modern dell screen as well as various TV's.

Any advice?