Diagnostic LED flashes once, but PSU works

Essentially LED #1 flashes once, and then goes off. I’ve read a lot over it, and it seems like it would be a Power Supply issue. However, I have replaced said power supply, and been shocked by it (twice now) when trying to verify that all parts are working. I don’t have the current equipment to try and verify pin outs, as the multimeter leads have been burnt out. Now essentially I need verification that this is a fixable issue, but having no feedback when trying to diagnose this machine is becoming increasingly frustrating. So any feedback would be greatly appreciated