I have an older soda machine with a Mars TRC-6800 changer that has been giving me fits. It gets to the point where it will accept very few coins so I run the calibration procedure and it runs fine for a few weeks then it gets picky again. I have about 3 different changers that do the same thing. Do these things have a battery backup that holds calibration data that may be going bad or are the coin sensors just that bad? I know these changers are obsolete. Is there a more modern changer that would work?