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RAP 2.17 Hydraulic Unload and Flow
Valves
Outputs 11 and 26
The hydraulic unload valve is normally open and
prevents pressure from developing in the hy-
draulic system while the machine is idle. When
the unload valve closes, pressure develops in
the hydraulic system.
The hydraulic flow valve provides cushioning at
the bottom of each knife stroke by allowing vary-
ing amounts of hydraulic fluid to flow back to
tank near the end of the cut stroke.
Possible Fault Indicators
The knife assembly will not move.
The knife assembly stays down and flow
passes over relief valve.
Motor starter overload shuts off the hy-
draulic motor.
"Knife failed to leave up
limit in time" message is dis-
played.
Knife assembly cuts with high impact
even when cushioning is set high.
Initial Actions
Check for loose or damaged wires 84 and 86 at
the electrical panel.
Procedure
1. Does the knife assembly cut with low impact
as cushioning is INCREASED?
Y
N
Disconnect power and replace the propor-
tional cartridge valve (PL 5.23 Hydraulic
Power Unit – 60Hz 59010).
CMT-130TC Book Trimmer
2. Run the machine through a cycle. Do output
LEDs 11 and 26 (GP 6.3 Input/Output LEDs)
switched on before the error message dis-
plays?
Y
N
Go to RAP 2.5 DC Power and check the 24
VDC power supply. Is the power supply
okay?
Y
N
Disconnect power and repair the 24
VDC power supply.
If LED 11 does not come on, disconnect
power and replace the main PWB (REP 4.23
Main PWB Replacement).
If LED 26 does not come on, disconnect
power and replace the console PWB (REP
4.24 Console PWB Replacement).
3. Switch the main power OFF and remove the
lower left door.
4. Remove the solenoid connector from both
the unload valve and the flow valve (Figure
2-20).
5. Short wires 84 to 74 and 86 to 74.
6. Place a Murr solenoid adapter between the
Hirschmann connector and the unload valve
solenoid (Figure 2-20). Switch the main
power ON and take note if the LEDs on the
adapter switch on. Repeat this for the flow
valve. Did the LEDs switch on in both
cases?
Y
N
Go to GP 6.12 Hirschmann Connector. Was
there a loose or shorted wire in a connector?
Y
N
Check for loose wire 74 at the electrical
panel.
Check circuit breaker CB8.
MAY 2019
2-25
7. Switch the main power OFF. Remove the
unload valve and flow valve solenoid coil
from the valves (with cables connected).
8. Switch on the machine. Insert the metal end
of a screwdriver into the unload valve sole-
noid coil to see if it attracts the metal screw-
driver. Repeat for the flow valve solenoid
coil. Does the solenoid attract the screw-
driver in both cases?
Y
N
Disconnect power and replace the non-func-
tioning solenoid coil (PL 5.23 Hydraulic
Power Unit – 60Hz 59010).
9. Switch the main power OFF and remove the
shorts placed between wires 84 to 74 and
86 to 74.
10. Replace the unload valve cartridge using a
deep well socket. Did this correct the fault?
Y
N
Reinstall the good dump valve cartridge.
Disconnect power and replace the flow valve
cartridge (PL 5.23 Hydraulic Power Unit –
60Hz 59010).
Repair complete.
Figure 2-20. Hydraulic Flow and Unload
Valves
2. Status Indicator RAPs
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