Rectifier Bridge Check
Connect an Ohmmeter to the grounded heat sink and one of the three terminals. Then reverse lead connections to heat sink and same terminal. If both readings are the same replace the bridge. A good rectifier bridge will give one high and one low reading. Repeat test on all terminals. When this is done you will have checked all six diodes with two readings taken for each diode. Do not use high voltage such as a 110 volt test lamp to check bridge.