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From time to time on the Ham Radio e-Mail Lists I see the following type of message:
Help I hooked up the power backwards and now my equipment is fried.
Since an ounce of prevention is worth a pound of cure I offer the following solution:
As you can see if the output is matched Positive to Positive and Negitive to negative (It is suggested that the output be hardwired in), than it does not matter which polarity you hook up to the input. This is a simple and inexpensive way to protect your eqipment. Ignore my warning at your own risk. :-)
I have received feedback from this page and add the following:
The bridge circuit has two diodes in series at any time. Each diode may produce a forward voltage drop of about 1 volt or even more sometimes depending on the diode specs and forward current it is made to carry (As validation this is stated in the Handbook). With two diodes the drop in voltage may add up and a power supply of 13.8v may be seen as <11.8v. You might want to use power Schottky diodes for less voltage drop.
Another idea is to use just a simple diode in forward direction for such equipment. With only one diode the equipment will not work when polarity is reversed.
One more idea is to use a relay with the diode in series with the coil.
Thanks to Prasad AB3EH, Jim Shorney and Nigel Gunn G8IFF/W8IFF
One last thought from me. Radio Shack sells inexpensive keyed plastic power connectors. Heathkit used the 6 pin vertical and just used the bottom two pins. Well that's all I've got I hope it helps.
73s
Forrest WB5HQO
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