He is correct about the reverse polarity protection diode.
Follow the Positive (+) circuit board line
in from the power connector on the back of the radio. You should come to a
small diode. Make a note of which side of the diode has the silver band.
Unsolder the diode and head to the nearest electronics store or heaven forbid,
Radio Shack.
It is a standard 1n4000 (low power units) or a 1n4001...very inexpensive.
Put it back in with the silver band on the same side as the one you pulled out.
Should be ready to go.
Try this site.
http://www.njqrp.org/quickies/quickie2.html
Good luck 333

"Got RF?"