Do System Tests to Identify Defective Components
90 810430 Troubleshooting Guide Powermax65/85/105 SYNC
Test 3 – Output diodes
Do this test if you get the 3-51-1 or 3-52-0 fault code.
1. Set the power switch on the plasma power supply to OFF (O), and disconnect the power cord.
2. Remove the plasma power supply cover and the component barrier.
3. Put a multimeter in ohmmeter (resistance) mode or diode test mode, and measure the
resistance on all 4 diodes in the bridge. For each diode, put the black (common) lead on 3.
Refer to Figure 16. A diode that is operating correctly gives the following values:
The value is open (very high resistance) with the meter leads in one direction.
The value is within the range of 0.1 V – 1.0 V with the meter leads in the opposite direction.
4. If a diode has one of the following conditions, replace both output diode bridges. Always
replace output diodes as a pair.
The diode has a value less than 0.1 V. In this condition, the diode is short-circuited.
The diode has a value greater than 1.0 V in both directions. In this condition, the diode has
an open circuit.
Figure 16 – Output diode connections on the power PCB
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