Did the hardware test by pressing both apple-keys at start-up, i got garbage screen and then (see picture) error : RAM 0000100.

So the problem is the RAM. Bummer. Impossible to fix. I'll however try taking whole machine to parts, cleaning up and checking the RAM solderings, if anything could be done. But this machine starts to look like an "parts only" and need of a replacement motherboard is in place.

Good link i found :

http://support.apple.com/kb/TA38047?viewlocale=en_US

I got my hopes up getting and working Apple II-family machine. Now i really need to find working //c or an IIe !