Komatsu 830E-AC Shop Manual page 216

Diode Board - DB1
Diode board (18, Figure 3-1) contains 24 replaceable
diodes that are mounted on a plug-in connector for
easy replacement. Some of the diodes are used in
the coil circuit of various relays to suppress the
resultant coil voltage spike when power is removed
from the circuit, preventing damage to other circuit
components (lamp filaments, etc.). Other diodes are
used to control the flow of current in a circuit as
required. Resistors or diodes may also be installed in
sockets P7 through P12.
Refer to the electrical schematic in Section R of this
manual for specific circuits.
FIGURE 3-2. DIODE BOARD
1. Mounting Rail
2. Screw
3. Nut
4. Mounting Plate
D3-6
5. Foam Block
6. Board
7. Diode
24VDC Electrical System Components
If a diode failure is suspected, remove and check the
diode as follows:
1. Grasp the diode connector, compressing the
locking "ears" while pulling the connector off the
board. Note the connector "key" used to ensure
correct polarity.
NOTE: Some digital multimeters are designed to test
diodes. If this type is used, follow the manufacturer's
instructions for proper test.
2. An analog ohmmeter can be used to test the
diode as follows:
a. Place the meter on the "X100" scale.
b. With the red meter lead (+) on the banded
end of the diode and the black lead (-) on the
other diode lead, the meter should read
between 1000 and 2000 ohms.
c. Reverse the meter leads and read infinite
resistance.
3. If no resistance is read on the meter, the diode
is open and must be replaced.
4. If the meter reads zero ohms, the diode is
shorted and must be replaced.
5. Orient the diode assembly for proper polarity
("key" noted in step 1.) and insert connector
until locked in position on mating receptacle.
10/06 D03036