Sharp UP-700?

Hi Alan. When you see key barrel, are you referring to the clerk key lock in the front of the machine that takes the black plastic keys?
the most common reason for trouble is when liquids are spilt on the machine. The get inside and foul up the switches. You can try squirting a small amount of de-watering fluid such as WD40 in the hole, then pull the key in and out a few times to see if it has cleared.
New clerk keys can be obtained from Sharp, but they are often very expensive. Don't ask me why. Sharp seem to just add 1000 percent markup to everything!

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If anyone needs a manual for a Sharp UP-700, C-tech has them here:

http://the-checkout-tech.com/manuals/cashregisters/Sharp9.php

Registerman
February 2011