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5-8. Relay Box
The power supply is directly connected to the relay
contacts. When these contacts are closed, 24 volts
is supplied to the solenoids which are mounted on
the hydraulic mini-valves. One relay is used to supply
power to the pump/motor and is always activated
no matter what control function is selected. The
brake locking circuit relay is also activated when
any control function other than BRAKE UNLOCK
is initially selected.
Also, inside the relay box is a step-down transformer
and full-wave rectifier which decreases the voltage
to 5-6 volts. This low voltage potential controls the
relays by the use of the hand-held pendant control
buttons. Basically the relays enable a 5-6 volt po-
tential to control the 24 volt circuit.
The following tests will determine if the relay box
is functioning correctly.
a. Checking Relay Box Input Power
1. Connect power cord to table. Plug the power
cord into the 120VAC supply (wall receptacle). Dis-
connect connector CN4, leave all other connectors
connected.
2. Using a DC voltmeter, test input power for
both the BATTERY and AC120V operating modes.
See figure 5-11. Meter should read approximately
24 -28 volts.
b. Test Results:
If you do not receive the correct meter readings,
the problem is in the input wiring, connectors or
components. If the correct readings are obtained,
proceed to the next step.
Figure 5-11. Relay Box Input
c. Checking Output to Pump
1. Make sure all connectors are connected and
activate the AC120V operating mode. See figure
5-12.
Figure 5-12. Output to Pump
2. Test HN4 at pin 1(+) and pin 2(-) with a DC
voltmeter. Meter should read approximately 24-28
volts when any function button is activated. If no
voltage is present, use an ohmmeter to test the
continuity from HN4 to CN4 (red and black wires).
041905.011
1-RED (+)
2-BLUE (-)
2
1
CN4
BATTERY MODE TEST (main power OFF)
5-PURPLE (+)
6-BLACK (-)
CN4
AC120V MODE TEST (main power ON)
CONNECTOR CN4 COLOR CODE
1
2
3
4
5
6
RED
BLUE
RED
BLACK
PURPLE
BLACK
7
8
9
10
11
12
WHITE
WHITE
YELLOW
GRAY
ORANGE
- - -
6
5
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