Apple Lisa Power Supply Repair

Hello, Does anyone out there have any words of wisdom for someone looking into repairing an Apple Lisa power supply? I have 3 power supplies, 2x 1.2A and 1x 1.8A, and each has its own set of issues. One is just plain dead, the safety switch engages OK but nothing powers up. Another one, the 1.8A unit, pops the GFI on the circuit as soon as it is plugged in. The third one makes a chirping sound when the power switch is pressed. The chirping continues as long as the switch is pressed. The PS that trips the GFI was working fine about a year ago but seems to have some issues now. Each power supply was tested in two different working Apple Lisas. Each has been opened up and each looks fine, no noticeable damage, scorches, ect. If anyone has had similar problems I would be interested in any solutions you came up with. Thanks, Nick