I pulled an old Astron power supply out of mothballs today. It's a
13.8 volt / 20 amp supply (the RS-20A). I find that there's a
noticeable hum when I plug it in, and I also notice that a small
output voltage of one volt or so is measureable on it even when it's
turned off and unplugged.

What should this tell me about the condition of this supply? As it is
I'm nervous about using it.

Thanks,

Steve