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I have two pieces of gear that I use sometimes that were made before the 3-prong cords came along, I guess. One is a ~1968 Marantz stereo amp, and one is the 1938 Hammond amp I just bought. Is there any way I can ground these correctly for safer operation?

There is . . . buts its not quite as straightforward as you might think. And I don't want to walk you through a procedure that might kill you if done wrong.

But there is a simple alternative:

Plug in the Marantz. (Nice amp, btw.) Turn it on. Hold your hand so that the very tips of your fingers touch the metal of the face plate. Using a very light touch, slide your hand sideways on the metal of the faceplate, so that you are just barely dragging your fingertips across the metal.

Reverse the plug in the wall socket, and do it again. In one direction, your fingers will slide smoothly. In the other, you'll notice a slight vibration in your fingertips. Note which way the plug is in the wall on the way that did not produce the vibration.

Make a mark of some sort near the prong that goes to the small sized outlet hole, and always plug the Marantz in with that orientation. You now have the same degree of electrical protection as a three-prong cord.

btw - if your fingers don't quot;vibratequot; in either direction, its a well designed unit that won't really benefit from a three-prong cord to begin with.

Hi Artie - Thanks for the reply.
The primary reason I asked about the Marantz is that last time I used it, I was running a mic through it, and was getting the vibration-shocks on my lips, and when combined with any moisture, it got almost painful. I had never experienced it before, so perhaps I had always gotten lucky with the orientation of the plug.
Is there a similar thing I could do with the Hammond too, or is that even a problem? (I really know very little about ground-circuits and stuff, so excuse my ignorance )

When you get that little quot;shockquot;, try reversing the plug. You're doing the same thing as my quot;finger testquot; . . . just you're doing it the hard way.

The Hammond might work with this test. The reason that this test works at all, is because they quot;ground referencequot; one side of the power cord with a 3 to 10 meg resistor. I think thats a more modern technique, that may not have been implemented in the older equipment - ergo, it won't matter in the older stuff. Still, you can try it and see.

Keep in mind, a good tech should be able to add the three prong cord for a reasonable amount of money. But don't be surprised if not all tech's know how to do it. I've worked with them before.

Alright, thanks again Artie. I wouldn't want to try and do any modding on the Marantz anyway, just because it's a great little amp. The Hammond... maybe after some education on it. But as far as the Hammond goes, if I want to use that amp together with other equipment, would I want to have a tech ground it?

Thats sorta hard to say. Obviously, in its day, the Hammond would have been designed to work with other equipment. As long as its in good working order, there's no reason to assume it wouldn't be good today. On the other hand, I can't imagine that there would be any harm in grounding it. Just make sure you find a competent technician. This is one of those situations where an quot;old guyquot; might be better. (One who's done this type of work before.)

btw - What kind of Marantz is it. I have an old 1030 integrated amp. Not quite as old as yours, but still cool.


Originally Posted by ArtieToobtw - What kind of Marantz is it. I have an old 1030 integrated amp. Not quite as old as yours, but still cool.

IIRC, it's a 1060. My dad and a buddy bought it during high school (graduated around '70 - I don't recall which year exactly) and it still works wonderfully for stereo and instrument amplification. Phenomenal piece of equipment.