Thanks for the replies. I was hoping to find a blown fuse, no such luck, the power supply doesn't appear to be protected. I thought the same thing Speedskater, that undervoltage wouldn't cause a meltdown and that pulling the plug wouldn't be different than flipping the switch. But with my rudimentary electrical skills I was sure I must be missing something. Perhaps Elizabeth is correct and a diode failed.
JohnR was kind enough to send me this unit many years ago. He was using it as a desktop DAC-headphone amp and thought it sounded terrible. He was right, the very powerful headphones sectioned sounded like caca. But at the time I had only a pair of cheap JVC phones and used it as the DAC in my main system, where the dual Wolfson chips sounded great. Thanks so much John, I got your money's worth out of it, returning it as a desktop amp at the end. The sound of the amp seemed to mellow lately and I've been using it as a change of pace from a Sabaj mini. It will now be employed as a fancy doorstop.