For a seasoned tech, you should know that "various voltages" are supplied from the PSU. Besides trying to measure any, the usual result, is maybe fans or CD drives open and close, suggests that 12V is OK. However, it takes 5V and below to run the logic, etc., thus it acts up. Overall, there's no time to fiddle with it if you can swap it out. I've tore down many a PSU and rarely are they fixable or want to. Overall, it's a waste of time and effort unless it has to be done. It's just the way to go. good luck
That was hard to fit into 60 characters..but here is the full question. If my PSU is failing , or next to death, will it at least send enough power to the MOBO to make POST beeps? Also the CPU won't turn on or show anything on any monitor, nor any POST beeps.