Amp gauge pegs

Hi, When I turn my ignition on, the amp gauge pegs at negative.  When I start it, it pegs at positive for a bit then looks normal.  I have had the battery tested and replaced the alternator,  Seems to run just fine, but it has never done that before.  It is a 72 and any help is appreciated.

Thanks for all the help!  figured it out

Great what was the problem and how did you find the problem.
Sal C                     nosal1