Komatsu 830E Shop Manual page 153

DIODE BOARD 1
The truck is equipped with a diode board (1, Figure
3-8) containing replaceable diodes (4). 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 cir-
cuit as required. Resistors may also be installed in
sockets P7 through P12 (3).
Diode Testing
Refer to the electrical schematic in Section R of this
manual for the specific circuit and diode to be tested.
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.
D03026
1. Diode Board (DB1)
2. Connectors (P1 - P6)
CIRCUIT BREAKERS
Table I on the following page lists the circuit breakers
on the truck, their function and location.
Additional circuit information can be found in Section
"R", Electrical Schematics.
24VDC Electrical System Components
FIGURE 3-8. DIODE BOARD 1
3. Sockets (P7 - P12)
4. Diodes (D1 - D23)
D3-13