Komatsu 830E Shop Manual page 145

Hot Switch Inverter
The Hot Switch Inverter Card in slot 3 (3, Figure 3-2)
is used to operate and test the service brake indica-
tor light. In normal conditions Q4 transistor is off and
the Indicator Light is off. When the stoplight switch is
activated, 24 volts is sent to pin "E" of the Hot Switch
Inverter Card. Transistor Q4 is turned on by this volt-
age and, in turn, grounds the service brake Indicator
Light. There is no alarm horn operation with this card.
A second circuit on this card is used to operate and
test the Retard Speed Control indicator light. When
RSC is turned Off, transistor Q7 is off and the indica-
tor light is off. When RSC is turned on, 24 volts is
sent to pin "J" of the card. This voltage turns on Q7,
grounding the indicator light circuit.
Hot Switch Inverter Card (Slot 4) (Not Used)
Temperature
The Temperature Card is used to turn on the High Oil
Temperature Indicator Light. The indicator light tells
the operator hydraulic tank oil temperature has
exceeded acceptable levels. Normal temperature
setting is 204° F (96° C). As the temperature goes up
the resistance in the probe decreases providing a
ground path for the indicator light and alarm horn.
Oil Level
The Oil Level Card is used to turn on the Low Oil
Level Indicator Light to warn the operator engine oil/
hydraulic tank oil level is below acceptable levels.
The oil float is connected to a variable resistor. As the
oil level decreases, the resistance goes down caus-
ing Q3 to turn on, grounding the indicator light and
alarm horn.
Temperature and Latch
The Temperature and Latch Card (5, Figure 3-2) has
two circuits to operate two different indicating lights.
The temperature circuit is controlled by a coolant
temperature sensor which decreases electrical resis-
tance as its temperature increases. It will have a
resistance of approximately 1000 ohms at 185° F
(85° C) and 500 ohms at 250°F (122°C). Normal set-
ting is 204°F (96° C).
When the temperature is low and the resistance is
high, Q1 is off and no high temperature indication
occurs. When the coolant temperature is excessive,
resistance decreases to a point where Q1 will turn on
and ground the flasher through D8, the alarm horn
through D12, and the High Temperature Light
through terminal D8. R14 can adjust the temperature
(resistance) at which the circuit is activated.
D03026
NOTE: Some electronic engine controls monitor
coolant temperature. If the engine controls monitor
the circuit, a 2K Ω resistor is installed to replace the
temperature sensor and disable the AID system
circuit.
The Latch Circuit monitors the accumulator pre-
charge pressure switches. When one of the pressure
switches closes, Q5 will be turned off which supplies
power to the gate of SCR Q7. With Q7 turned on, Q9
will supply the ground path to turn on the Low Accu-
mulator Precharge Indicator Light and sound the
alarm horn. The Indicator Light is connected to 12F
and will flash off and on. The SCR will remain on until
power is removed from the card by turning the key
switch "Off".
Coolant Level/Flasher
The Coolant Level and Flasher Card (6, Figure 3-2)
contains two separate circuits. The flasher circuit at
the top of the card has Q12 transistor biased to be
saturated when no malfunction is present, resulting
in there being 24 volt positive output on pin "H" of the
card and on wire 12F. When a indicating circuit is
activated, the ground side of the circuit connected to
card pin "K" is grounded. Q12 will turn off initially and
then after a delay, adjusted by R20, will turn on and
off to give the intermittent 24 volt output.
The other half of the circuitry on the Coolant Level
and Flasher Card operates the Coolant Level Light.
The Water Level Probe connected to terminal B11
grounds the 31L circuit when the coolant in the radia-
tor is above the probe position. The coolant saturates
the probe and electrically grounds the circuit. When
the circuit is grounded, Q6 transistor is off, resulting
in no indication. When the coolant level drops below
the probe, 31L is no longer grounded and Q6 turns
on to ground the flasher through D5, ground the
Coolant Level Light through terminal D11, and
ground the alarm horn through D6. The light and
alarm horn will operate intermittently as their 24 volt
supply is from circuit 12F, the flasher output.
NOTE: Some electronic engine controls monitor
coolant level. If the engine controls monitor the
circuit, a 2K Ω resistor is installed to replace the
probe and disable the AID system circuit.
Lamp Test
All of the card circuits are connected to the Lamp
Test Switch on the overhead display area. In normal
operation, these circuits are open and not functional.
When the operator pushes the Lamp Test Switch, it
activates all the indicator circuits by grounding them.
This is used to verify that all lamps are functional.
24VDC Electrical System Components D3-5