The Double Pole Single Throw DPST relay is the equivalent of 2 SPST switches (NO Normally Open and NC Normaly Closed) and can be used to switch 2 different loads. As you can see in the schematics ...

The AZ733W is a series of Dual-Pole Single-Throw (DPST) switch power relays that are offered in miniature sizes, best suited for applications that require lesser board space. The devices’ coil power ...

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 ...