[vcf-midatlantic] Old AT power supplies - how to test?

Hey folks, I have a couple of old DOS/Win98 (OS/2) era systems that I came across, and they both have AT PSUs I want to check out before powering on for the first time. I was thinking before powering on: - Open the PSU - Air spray the PSU - Look for obvious signs of failure - capacitor leakage, burnt PCB, burnt components If all looks OK - do these require a load, or can I at least test basic voltage with no load? I do have heat resistors (used to balance out ATX PSUs for a 3D Printer) that I believe I can plug in on the 5V or 12V rails and test voltage there.. How much testing should I do / what do you recommend? Thanks! John