I got the amplifier and turntable back from the shop Friday, only to find the AC hum was still there, dammit! Some swapping of input plugs isolated the problem: the turntable was causing the hum. I could plug in anything else I liked and get no more than an open-circuit hiss, but the second one of the turntable plugs went in, the hum came back.
So I dragged it back over to the stereo shop Saturday afternoon, and the owner put it on the bench while I watched him confirm that yes, the turntable caused a hum in his bench amplifier, as well as my own. He tried wiring a ground patch, but it didn’t help, at which point I decided the problem was that after ::mumble::-teen years, the turntable’s electronics had just worn out and given up. This didn’t surprise me, ’cos it was only a mid-line model, so I doubt Onkyo dropped in any really good electronics to start with. I’d already started thinking of getting something else better.
So the turntable giving up didn’t change anything, it just pushed up my schedule. I asked the shop owner what he might have that would do me, and he came back with a late-70s Sony PS-T22 direct-drive that had been upgraded with an Ortofon FF 15E Mk II cartridge. The dust cover hinges are busted (but may be fixable; I’m pondering ways and means) and it has a few gouges across the top, but cosmetics aside, the mechanics run very nicely. I gave him the Onkyo and $75 boot, and left with the Sony. I came home and reconnected everything—and as the Who LP I’m playing at the moment is proving, the Sony turntable kicks the Onkyo’s ass.
