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Dagu Rover 5 Asymmetrical Encoder Output Problem

I'm having problems with Dagu Rover 5 with asymmetrical encoder outputs.  They do not have a 50% duty cycle and when the two outputs are decoded they don't give the same count going forwards as backwards.  I'm using 74HC14 Schmidt Triggers with a Teensy++ 2.0 and 4x encoder library.  My fix is to count by 1's going forwards and 1.75 backwards.  Is there a way to fix these encoders to have a 50% duty cycle?Dagu Rover 5 Encoder Output

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This chassis passed QC in 04/12 and has optical encoders.  The circuit board is double sided and looks to have the same circuit on both sides.  The pots are mounted on the bottom side such that you have to remove the board, make an adjustment, screw it back down, close up the case, and run the motors.  Doing so allowed me to get a near perfect 50% duty cycle even though one pot was bottomed out.  The encoders now decode properly and give the same count in both directions. That's probably why they went to Hall Effect though.  I'm going to take it up with Pololu and try to get the chassis swapped out for a new one.