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Determing DC power input polarity

Hi all,

I bought a ton of surplus electronic gear (almost literally) and among some of the cases of odd bits and whatnot I came across an AOR AR3000 "communications receiver" (I use quotes as it's nothing like any *proper* CR I've ever encountered, but I guess that's my age prejudice). Anyway, it has 3 pins on the back panel marked "12V DC in" but no polarity indication. I'm guessing one of those pins is just for alignment to ensure the plug goes in the right way around and the other two are pos and neg. I can find no power lead for this radio. Is it possible to determine which pins are which from carrying out some basic resistance measurements between them? I really don't want to hook it up the wrong way around. BTW, the service manual I have downloaded off the net does not help at all in this respect.

TIA.

Reply to
Cursitor Doom
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Does the sm tell you what kind of polarity prot. there is, or not? Wrong way and zilch or wrong way and more than .6V blows a fuse etc.

Reply to
N_Cook

But if there is a diode across the DC line, that would show the polarity.

Other than that, or finding details online, one could open it up and see which pin goes to ground. At this point, negative ground is the norm. Find where the other pin goes, presumably to an electrolytic, and its polarity markings will provide secondary information.

Michael

Reply to
Michael Black

Google "AOR AR3000 power connector" and look at the images. There is one where someone adapted two individual wires to that socket. Red is on the right and Black on the left (as seen from the back)..

Separately, someone mentioned that older Hayes modems used that same connector. I don't remember that but it's possible. Maybe your tons of surplus includes some of those.

Pat

Reply to
Pat

There may well be the plug for it somewhere among the vast amount of STUFF I took delivery of. However, I tried out Michael's suggestion of taking it apart and there was a large electrolytic across the pins in question internally, helpfully marked, just as he said. :) So - for the benefit of anyone in future trying to look this info up - looking at the socket from the rear, the neg pin/gnd is on the left; the right is +12V and the top pin is n/c.

Reply to
Cursitor Doom

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