Procedure For Testing Diodes - Komatsu Galeo PC138US-8 Shop Manual

SEN02460-01

Procedure for testing diodes

a Test the assembled-type diode (8-pin) and the
single diode (2-pin) according to the following
procedure.
a The conductive directions of the assembled-
type diode are as follows.
a The conductive direction of the single diode is
indicated on the surface of the diode.
1. When using digital circuit tester
1) Set the tester in the diode range and
check the indicated value.
a When an ordinary circuit tester is
used, the voltage of the internal bat-
tery is indicated.
2) Apply the red (+) lead of the tester to the
anode (P) side of the diode and apply the
black (–) lead to the cathode (N) side and
check the indicated value.
3) Judge the condition of the diode by the
indicated value.
The indicated value does not change:
q
The diode does not have conductivity
(Defective).
The indicated value changes:
q
The diode has conductivity (Normal).
Note: In the case of a silicon diode, a
value in the range from 460 to 600 is indi-
cated.
8
1
2. When using analog circuit tester
1) Set the tester in the resistance range.
2) Apply the leads of the tester as explained
below and check the movement of the
pointer.
i) Apply the red (+) lead of the tester to
the anode (P) side of the diode and
apply the black (–) lead to the cath-
ode (N) side.
ii) Apply the red (+) lead of the tester to
the cathode (N) side of the diode and
apply the black (–) lead to the anode
(P) side.
3) Judge the condition of the diode by the
movement of the pointer.
The pointer does not move in i) but
q
moves in ii): The diode is normal (The
moving range (resistance) depends
on the type and selected range of the
tester, however).
The pointer moves in both i) and ii):
q
The diode is defective (Internal short
circuit).
The pointer moves in neither of i) and
q
ii): The diode is defective (Internal
disconnection).
30 Testing and adjusting
PC138US, USLC-8