what the heck is a Namiki DF-100 Direction Finder

Seasoned has it largely correct. The device senses dc leakage voltage and goes with the orientation of the plug that has the lowest voltage. I would disagree, however, on how frequently you hear a benefit. You can accomplish the same using a volt meter and a contact to ground. You touch the chassis or a grounded part and go with the lowest reading.

If you hear a difference and are a purist, you can reverse the connections to the ac plug within the unit and get the results you want without using a cheater plug.

I bought a Namiki long ago and probably have not used it in 15 years. Since most of my equipment is by small manufacturers, I find that they consider this.

As I recall, there were reliability issues with this thing, so if it doesn't work for you, don't blame yourself. Good luck, Dave

Tbg writes:
"You can accomplish the same using a volt meter and a contact to ground. You touch the chassis or a grounded part and go with the lowest reading."

I beg to differ. When you check leakage against ground, as you suggest, you're measuring "leakage against ground", which is helpful, but this is NOT what the DF-100 does.

It does not measure "against" anything. It is a single lead sampling device that detects an electrostatic field. Since these fields can have the equivalent "zap" power of several kV, it is helpful to minimize these, especially to protect solid-state electronics.

But truthfully, I don't quite understand how it works.

I've discussed my theories in my current EBay listing (I'm selling mine), but I must admit that I'm perplexed how it detects "proper polarity", with no ground connection.

Could this be a really advanced gadget that is not recognized because of lousy instructions? Or quackery?

radioman, I always wondered how the Namiki worked without a ground, but in probably 20 instances where I tried the volt meter versus the Namiki, they gave the same results. I also like to know the voltages both ways. Sometimes I am shocked by the high values.

Seasoned- Would you still have a copy of the Namiki instructions that you could share with me?  I recently purchased one but the previous owner did not have the instruction sheet.