During evaluation, I reversed the polarity of the supply voltage (24V) for the Tormach 1100M/MX board (ECM v1.5). As a result, I blew a capacitor (C79) and two diodes (D22/D23)off the board. Tormach is only willing to sell me a new board. I'd rather see if it can be fixed first.
I can identify the diodes (IT4) that are blown off, but I don't know the capacity of the damaged capacitor C79 (1.6 x 0.8mm). One side of the capacitor pad is directly connected to ground (24V-) with less than <0.3Ohm resistance. The other pad is connector to resistors (R67, R36-37 and Diode D20). My best guess is that this capacitor is part of a voltage spike (CR) suppression circuit. But, I have no idea what the capacitance should be. Any help would be much appreciated. If you think any other portions of the circuit should be replaced as well, please let me know.
Thanks!