Not ever having seen the internals of an Imsai, I obviously can't say anything even remotely definite. However, you may see this behavior on older electronics that have capacitors between line voltage and ground. (This was popular in tube stereos and TV's for many years.) Eventually, the capacitors would leak, and you'd get a low-current tingle when you touched the chassis. Very scary. Some surge supressor circuitry is designed with MOV's between Hot-and-Neutral, Hot-and-Ground, and Neutral-to-Ground. It may be possible that you have leakage in the MOV's, and your connection to ground is weak or missing. Since it's fairly common to tie the ground to the chassis, that COULD be a source of the 60hz wave you're seeing, whether the MOV's are inside your unit, or inside an attached power strip. I would check your electrical grounds first. Also check for power supply wires hitting the chassis, or even a cable with the insulation worn through. Is the power supply a switching unit, or a traditional linear power supply ? I have two laptop power supplies, made by different manufacturers. They are two-wire (ungrounded) plugs. When plugged into my laptop, both will give me a slight tingle when I touch the metal speaker grills on the laptop, and a source of ground. Yes, metal speaker grills. It's a 233Mhz Thinkpad. ;-) It may be something inherent in the design of the switching power supplies. It might be helpful to disconnect the power supply any AC readings off of the outputs. T