Tweco 400 MST Arc Master - Manual (Page 96)

APPENDIX 4 DIODE TESTING BASICS
9
APPENDIX 4 DIODE Testing Basic DIODE TESTING BASIC
Testing of diode modules requires a digital Volt/
Ohmmeter that has a diode test scale.
1. Locate the diode module to be tested.
2. Remove cables from mounting studs on diodes
to isolate them within the module.
3. Set the digital volt/ohm meter to the diode test
scale.
4. Using figure 1 and 2, check each diode in the
module. Each diode must be checked in both
the forward bias (positive to negative) and
reverse bias (negative to positive) direction.
5. To check the diode in the forward bias direc-
tion, connect the volt/ohm meter positive lead
to the anode (positive, +) of the diode and the
negative lead to the cathode (negative, –) of
the diode (refer to Figure 10-1). A properly
functioning diode will conduct in the forward
bias direction, and will indicate between 0.3
and 0.9 volts.
6. To check the diode in the reverse bias direc-
tion, reverse the meter leads (refer to Figure
10-1). A properly functioning diode will block
current flow in the reverse bias direction, and
depending on the meter function, will indicate
an open or "OL".
7. If any diode in the module tests as faulty,
replace the diode module.
8. Reconnect all cables to the proper terminals.
Figure 10-1: Forward bias diode test
Figure 10-2: Reverse bias diode test
COM A VR
Anode Cathode
Forward Bias
Diode Conducting
COM A VR
Anode Cathode
Reverse Bias
Diode Not Conducting