Measuring the voltage across C1724 is 300V normal, indicating that the ballast input voltage is normal; then measuring the voltage across C1721 is 0V, the normal value should be 200V, showed the chopper circuit failure. FB1701 has been blown detected, thus determine the presence of the chopper circuit overcurrent. The Q1701 remove the testing, found the drain (D) and gate (G) has been the breakdown between. Replace the Q1701, troubleshooting.uCaservice manual download site