I did that with avionics, first rule was check power supply voltages, then pop the scope probe on them, and look at the ripple voltage there. Not too concerned about value if under 100mV pp but always checked there were no missing points with a failed diode, or that there was not a big hump of shorted diodes. Some of the secondaries were fine as they had a high resistance, so would be fine for a while with a shorted diode, but not the 5V rail, which had a nasty failure of making a box full of compressed smoke, and failing eventually by blowing 2 of the mains fuses after the transformer had melted itself into a pool of goo along the entire cabinet. Yes, even those were repairable, but the cost, plus the time to redo almost half of the wire wrapped joints to replace the connectors buried in the goo, and the cleaning. PSU itself would simply be dropped into the bin of stuff for secure destruction, no way to fix that economically, even at the price of the replacement ones, you kept 3 screws and changed the rest.