[Tubejunke]

There really is no connection to the metal body of the probe. That stops at the plastic end and is isolated. There is almost no resistance from the chassis to the probe end ground connector. No resistance between the ground side (braided) and the center conductor. No change if I reverse the plug. The unit is quiet until I hook up the probe, so I feel the problem is there. If it hummed as it once did when I got it I would suspect power supply filter caps. 4X 20mfd. and all replaced although not the best job in the world stuffing them under the chassis. I took three of the very leaky caps out of circuit, but left one in jumping across it. I know that is something people do, but is deemed a no no by good techs. Again though, I think if I had a problem there that I would have hum with or without the probe connected, but maybe I'm wrong.

I edited to ad that I can clip the ground lead to the probe tip and quiet the noise. Of course that is shorting the whole probe as far as I know. I have heard of the crystal diode becoming faulty or shorted. I know it's not open. I would think that if the diode were shorted that it wouldn't pass a signal, but it does. I hate being stumped on such an utterly simple circuit. Thanks a ton though for reading in and giving input!