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TROUBLESHOOTING AND REPAIR |
SCR BRIDGE TEST(continued)
FIGURE F.14 – SCR BRIDGE ASSEMBLY
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ANODE
CATHODE 
REMOVE
INSULATING
PAINT
PROCEDURE
STATIC TEST
1.Disconnect the input power from the
2.Remove the top and side panels and drop the nameplate to access the PC Boards.
3.Unplug the Molex connectors from both the Control Board and the Firing Board.
4.Scratch off some of the insulating paint from each of the six heat sinks (anodes) and the base plate (cathode). See Figure F.14.
5.Using the analog ohmmeter:
•Measure the resistance from each Anode to the Cathode plate with the Positive meter lead on the Anodes. The resistance should be very high or ‘open’.
•Reverse the meter leads and measure all the same points. The readings should be very high or ‘open’, and typically, will all be similar.
6.If any of the test points shows a low resistance, dis- connect the Snubber Board from that SCR. If the reading is still low, the SCR is defective.
7.Continue to the Active Test.
The Active test will require constructing a test cir- cuit or use of a commercial SCR Tester. See Figure F.15.
