Testing Diodes - Komatsu PC88MR-10 Shop Manual

Testing diodes

a Test the diode array (8-pin) and the single diode
(2-pin) according to the following procedure.
a The continuity directions of the diode array are
as follows.
a The continuity direction of the single diode is
indicated on the surface of the diode.
Testing
(PC220-E300-36J-P-00-A)
1. When using a digital tester
1) Select the diode range screen to check the
displayed values.
a When an ordinary circuit tester is used,
the voltage of the internal battery is
indicated.
2) Apply the red (+) lead of the multimeter to the
anode (P) side of the diode and apply the
black (-) lead to the cathode (N) side and
check the indicated value.
3) Evaluate the condition of the diode by the
indicated value.
Indicated value does not change: No
continuity (defective)
Indicated value changes: Continuity
(normal) (note)
Note: In the case of a silicon diode, a value in
the range from 460 to 600 mV is indicated.
The indicated value is 0 or approximate
0:
The diode has internal short circuit
(defective).
PC88MR-10
(ALL-E300-001-P-00-A)
30 Testing and adjusting
2. When using analog tester
1) Selects the resistance range screen.
2) Check the movement of the pointer when
performing the following connection.
1] Apply the red (+) lead of the multimeter to
the anode (P) side of the diode and apply
the black (-) lead to the cathode (N) side.
2] Apply the red (+) lead of the multimeter to
the cathode (N) side of the diode and
apply the black (-) lead to the anode (P)
side.
3) Evaluate the condition of the diode by the
movement of the pointer.
The pointer does not move by the above
1] connection, but it does by the 2]
connection: Normal (however, the
movement of the pointer (resistance)
varies by type of tester, or selection of
measuring range).
The pointer moves by either connection
of the above 1], and 2]:
Defective (internal short circuit)
The pointer moves by neither connection
the above 1], nor 2]: Defective (internal
open circuit)
Electrical system
30-129