Tweco 51 with SL100SV CutMaster - Manual (Page 92)

SERVICE 5-28 Manual 0-4640
5
B. Diode Testing Basics
WARNING
Disconnect primary power at the source before disassembling the power supply, torch, or torch leads.
Testing of diode modules requires a digital volt/ohmmeter that has a diode test scale. Remember that even if the diode
module checks good, it may still be bad. If in doubt, replace the diode module.
1. Locate the diode module to be tested.
2. Remove cables from mounting studs on diodes to isolate the module.
3. Set digital volt/ohmmeter to diode test scale.
4. Using the Figures for each test, check each diode in the module. Each diode must be checked in forward bias (plus to
negative) and reverse bias (negative to plus) direction.
5. Connect the volt/ohmmeter positive lead to the anode (+) of the diode and the negative lead to the cathode (-) of the diode for
forward bias testing (refer to following figure). A properly functioning diode will conduct in the forward bias direction and
indicate between 0.3 to 0.9 volts.
0.75
VR COM A
Art # A-00307
Anode
Cathode
Forward Bias
Diode Conducting
+
_
Diode Test Symbol
OL
VR COM A
Art # A-00306
Anode
Cathode
Reverse Bias
Diode Not Conducting
+
_
Testing Diode Forward Bias Testing Diode Reverse Bias
6. Reverse the meter leads across the diode for reverse bias testing (refer to following figure). A properly functioning diode
will block in the reverse bias direction and depending on the meter function will indicate an open or “OL”.
7. If a diode checks bad, replace the diode module.
8. Reconnect all cables.