Sorry I can't be more help. As you've had some success with SMC reset, etc., it sounds like the PSU is working (not that there is much that goes wrong with them apart from the cable fraying). If you get boot sounds (bong), it could be screen related issues, but I'm still thinking battery, due to the age of the machine. You could try and find a local mac specialist, if you're in Essex there will be a few.I’ve tried it both ways. Tried charging for hours. No joy.