Procedure For Testing Diodes - Komatsu WA900-3E0 Shop Manual

Testing and adjusting

Procedure for testing diodes

Procedure for testing diodes

a Test the diode array (8-pin) and the single diode
(2-pin) according to the following procedure.
a The conducting directions of the diode array is
indicated on the surface of the diode as shown in
the following figure.
a The conducting direction of the single diode is in-
dicated on the surface of the diode as shown in
the following figure.
1.
When using a digital multimeter
1) Set the multimeter in the diode range and
check the indicated value.
a When an ordinary circuit tester is used,
the voltage of the internal battery is indi-
cated.
2) Put the red probe (+) of the test lead to the
anode (P) of and the black probe (–) to the
cathode (N) of the diode, and check the indi-
cated value.
3) Check the quality of the diode from the indi-
cated value.
Indicated value does not change: the di-
q
ode does not have continuity (defective).
Indicated value changes: the diode has
q
continuity (normal). (See a below.)
30-6
a A value between 460 to 600 is indicated
for silicon diodes.
2.
When using an analog multimeter
1) Set the multimeter in the resistance range.
2) Apply the leads of the tester as explained
below and check the movement of the
pointer.
1] Put the red probe (+) of the test lead to the
anode (P) and the black probe (–) to the
cathode (N) of the diode.
2] Put the red probe (+) of the test lead to the
cathode (N) and the black probe (–) to the
anode (P) of the diode.
3) Check the quality of the diode by the move-
ment of the pointer.
The pointer does not swing with connec-
q
tion 1] above and the pointer swings with
connection 2]: Normal (Note that the
magnitude of the pointer's swing (indicat-
ing the resistance) depends on the given
multimeter model and the measurement
range selected).
The pointer swings with both connections
q
1] and 2]: Defective (internal short circuit)
Pointer does not swing with both connec-
q
tions 1] and 2]: Defective (internal open
circuit)
3 0 - 6
WA900-3E0