I feel your pain. I just finished repairing 5 of these gems this past month. Only one was easy. The one that had the type problem you are having had a processor issue. I switched them around and for some reason the machine came to life. (still have no reason why but it is still running) I did have to put new RAM in this machine also as I got the three blinking lights when it did respond.
If your other machine is in same year group and same speed you my try moving the processors over from it and see what happens.
Good luck with it.