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TROUBLESHOOTING & REPAIR
STATIC SCR/DIODE RECTIFIER BRIDGE TEST (continued)
FIGURE F.16 – HEAT SINK AND SCR TEST POINTS
DIODE DD
DIODES DA, DB, DC
REMOVE | ANODE |
INSULATING PAINT |
|
| CATHODE |
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9.Remove the red insulating paint from the heat sink test points. See Figure F.16.
NOTE: Do not disassemble the heat sink.
10.Measure the resistance from the anode to the cathode of SCR A, using an analog volt/ohmmeter (multimeter) set at R x 1000 scale. See Figure F.16.
a.Reverse the meter leads and measure the resistance from the cathode to the anode of SCR A. See Figure F.16.
b.If a low resistance is measured in either meter polarity, SCR A is faulty. Replace SCR A.
11.Test the resistance of SCR B and SCR C using the same procedure described in Step 10.
12.Measure the resistance of diode DD from anode (+probe) to cathode
a.Reverse the meter leads and measure the resistance from cathode (+probe) to anode
b.If a low resistance is measured in both meter polarities, diode DD is shorted. Replace diode DD.
c.If a high resistance is measured in both meter polarities, diode DD is open. Replace diode DD.
13.Test diodes DA, DB and DC for proper oper- ation using the same procedure described in Step 12.
14.Reconnect all leads and molex plugs.
15.If this test did not identify the problem or to further test the SCRs, go to the Active SCR
Test.
If the test is complete, connect plug J6 to the control board and plug J30 to the snubber board and reconnect lead #204B to resistor R1. Replace the covers to the two boards. Replace all case covers. (See the Case Cover Removal and Replacement proce- dure.)
