I've got a newly acquired Perform 550 for use with my IIe card however I just picked it up from its Orignal owner (he paid 2400 new for it) I paid 50 with everything he just wanted it to have a good home. Not used in a year fine when put away. But now I put it in and flip the rear switch and I hear the monitor energize really quick but nothing else. I push the keyboard power switch I add New PRAM battery, I toggle the power switch on the rear many times. I remember that the LC AIO series had some issue with this that wasnt a biggie but I don't remember the problem. Since it powers the monitor (charges it) I don't think it's the psu.