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Service Manual
Series T90 Axial Piston Pumps
Adjustments
Standard manual displacement control (MDC) adjustment
MDC Neutral start switch (NSS) adjustments
36 |
©
Danfoss | March 2020
than 1.5 bar [22 psi]. Reference Danfoss testing specifications TS-422 or Control Neutral Adjustment
instructions.
3. Turn neutral adjusting screw (or supply current/hydraulic pressure to solenoid C2) until the servo
pressure at port M5 is less than 1.5 bar [22 psi] greater than at port M4.
4. The system pressure differential must be greater than zero and the pressure at port A (B for clockwise
rotation) must be greater than the pressure at port B (A for clockwise rotation). This step ensures the
servo is in contact with the servo cylinder on side M4.
5. Slowly turn in the servo cylinder on the M4 side until the system pressure differential starts to
decrease. The servo pressure differential must be less than 1.5 bar [22 psi] during this step. Continue
turning in the servo cylinder until the system pressure differential is less than 1.5 bar [22 psi]. This
procedure sets the servo and swashplate to mechanical neutral.
There are no adjustable elements in the manual displacement control. Centering springs and washers on
each end of the control spool hold it in its neutral position. Since there is no centering spring on the
control input shaft, the shaft automatically assumes the appropriate position when the control is installed
on the pump.
The Neutral Start Switch (NSS) provides a means to prevent the system prime mover from starting while
the pump control handle is in-stroke. When the control input shaft is in its neutral position, the switch pin
engages a slot on the eccentric cam attached to the control shaft. This allows the spring loaded NSS to
close, completing the electrical starting circuit for the prime mover. When the control input shaft is not in
its neutral position, the eccentric cam opens the NSS switch.
The neutral start switch is threaded into the special lock nut for the eccentric plug. Turning the NSS
clockwise (CW) moves the NSS closer to the switch cam on the control shaft, and narrows the NSS
deadband. Turning the NSS counterclockwise (CCW) moves the NSS farther from the switch cam on the
control shaft, widening the NSS deadband. The switch pin is located in an eccentric plug which is turned
to move the center of the NSS deadband.
MDC with neutral start switch / View at section A-A
A
Control shaft
Switch cam
Eccentric plug
Switch pin
Special lock nut
for eccentric plug
Orifice check valve seat
Control spool assembly
Control link assembly
View A-A
A
Switch lock nut
Neutral start switch
P104 146E
AX216086485386en-000101
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