I'd guess you are looking at a cap failure in the original PSU. 386 era is what, early 90s. 30+ years is a good run. If a replacement PSU doesn't have a switch, you could always hook it to a surge ...
I'm upgrading an old PII 400MHz to a quiter case with a new hard drive. Old case had a ~200W PSU; new one is an Antec Sonata with a 380W PSU (overkill, true, but I need the quiet.)<BR><BR>I was ...