I recently restored a Jackson 648 Tube Tester. I did all the usual stuff, checked and replaced out of tolerance resistors, replaced the one lonely capacitor, gave it a good cleaning and replaced the power cord with a modern polarized one ensuring the hot lead was connected to the power switch as well as adding an in-line fuse to the hot lead.

It calibrated very well with all voltages coming within 3% if not dead on. I have been using the tester to test various tubes I have and I have no reason to suspect anything is wrong with it. On a whim last night I used my Fluke to check the voltage between the chassis and the ground plug on my house receptacle and I was surprised to see a reading of 64 VAC when the tester is powered on!

I wasn't expecting this. The schematic doesn't show anything grounded to the chassis and I checked for anything that may be shorted but didn't see anything. Poking around with an Ohmmeter checking resistances between the chassis and other components the lowest resistance I would get was around 500 meg when I got anything at all. I read an article that indicated parasitic capacitance might be responsible for this and isn't a concern because the current is so low. I also saw a thread on here were another fella had the same issue but it was because he used a DMM like me when he should have used a VOM. I don't have a VOM to check with. Should I be concerned and if so any ideas on what to check?

No need to worry.

Your meter probably has a high input impedance, in the megohms.

The tube tester's power transformer has a capacitance to core, probably many hundreds of pF.

Try, carefully, taking your DMM, ground one lead, and connect the other lead to the wall socket, the hot side, through a 500pF capacitor.

You will probably get a reading of several tens of volts.

Perfectly normal.

If it bothers you, put a 3-wire cord on the tube tester or run a grounding wire from the chassis to earth ground.

You can test for leakage by placing a resistor in parallel with your DVM. One volt across 1 K is 1.0 ma.

RRM

I appreciate all the feedback. I will try some of these suggestions out tonight when I get home. I take it this is a common phenomenon when the chassis isnt tied to ground. Thanks again.

Sounds like nothing more than so-called "leakage current" as others have already said. You've got to bear in mind that this was a piece of commercial equipment, and when it was manufactured, it did not necessarily have to meet the same standards as consumer appliances. Higher leakage current was not unusual in such instruments; they expected you to know enough not to work on a damp concrete floor in your bare feet!

Try setting your DMM to the 200-volt range (or assume it will get there on auto-range) and connect a 200-k ohm resistor--anything close will do, it doesn't have to be exact--across the probes. That will simulate a 1,000 ohm-per-volt VOM on the 200-volt range. You can do the same thing on the 20-volt range with a 20-k resistor, or a 2-k resistor on the 2-volt range.

As everyone suggested, it was nothing to worry about. I put a 2k resistor across the probes and the voltage drop was very small like .004 volts. I read up on leakage current and it all makes sense. Appreciate the enlightenment.