How do you measure a capacitor? Use a capacitance meter! Otherwise replace it.


How many watts (running amps) is the motor? What does it drive? Something with a lot of inertia? Why is there two of these circuits? two motors? Reversing? This is not obvious from the circuit.

When does the circuit fail? Always on startup? On startup would suggest a peak current problem, so a bigger triac might address the problem but you have to watch the holding current - triacs (and scrs) require a minimum current passing through them to keep them conducting so putting too big a triac on a small load causes problems. As I suggested previously, try using a solid state relay and placing the snubber circuit across it. If this doesn't solve your problem, then there must be something really fundamental that we're missing.