Ja Control; Operation; Functional Description; Signal Pressure - Danfoss 51 Series Service Manual

Service Manual

JA Control

Operation

Repair

36
Series 51 Hydraulic Proportional Controls Service Manual

Functional Description

JA control is a stand-alone, dual signal hydraulic proportional control. The control housing contains a
pressure compensating override (PCOR) valve, a brake pressure defeat (BPD) valve, and passages to route
oil to the 4-way valve and to the servo piston ends. An external servo supply pressure fed to port M5 is
required. A threshold spring and ramp spring(s) act on the opposite end of the 4-way valve.

Signal Pressure

Separate external variable signal pressures are fed into ports XA or XB. The BPD spool resolves which
signal pressure is higher and routes this signal pressure to the end of the 4-way valve. The signal pressure
shifts the 4-way valve and it ports servo supply pressure to the ends of the servo piston, changing motor
displacement in proportion to the signal pressure.
JA Control Schematic Diagram
XB XA
T4
BPD
U7
T6
PCOR

Disassembly

1. Remove PCOR lock nut (M14).
2. Remove and discard O-ring (M16).
3. Remove adjuster ( Z*).
4. Remove spring (M18).
5. Remove spool assembly (M20).
C
Caution
Do not remove PCOR valve bushing (M21).
11009446 • Rev BA • July 2014
Loop flush
L2 M4
A
max.
disp.
T2 T3
T1
T7 T8
B
M3 N
M1
n
L1
(M5)
X3
M2
P106 420E