My Mars Validator AE2412-U3E - 24V unit is malfunctioning. It accepts the bill but does not turn on timer. Do we replace or is there a company that fix these. If i replace it can i use other models because KR sell this unit for $339. I saw 2512 , 2601 , 2631 models on ebay. btw it is hookup to 1034 nonswipe timer.