Sony JB 940: The saga continues!
Well it's very strange, I disconnected the unit and transferred it to another location (my kitchen table), removed the case again, connected to mains, pressed On and it came on immediately, and the disc ejected normally. I didn't take any other action except glare at it. I've now put the MD back with the other equipment and it seems to be working normally. Go figure! Anyway all is well than ends well. Thanks for your interest and advice.
I'm now going for broke and re-connecting my Sony DAT machine, circa 1993. Wish me luck!
Mike