TROUBLESHOOTING 777 SERVICE MANUAL
10-36 Published 10-01-2012, Control # 045-08
Test 8 – Adjusting the Control Handle Potentiometer
A reaction of a crane system function in relation to hand
control movement may indicate a misalignment of the handle
potentiometer. Adjusting a single axis controller (crawler and
load drum handles) or double axis boom/swing handle
requires aligning the hand lever assembly and the
potentiometer in the neutral position. Neutral is the position
at which 5 volts DC is present from the potentiometer.
With engine off, connect a jumper wire between the normally
open (N/O) terminal on the neutral switch and terminal C on
the handle terminal block. Connect the positive lead of a
digital multimeter to terminal C and the negative lead to a
grounded contact.
For single axis controller adjustment, fully loosen the slotted
set screw with a screwdriver and allow the hand lever to
return to its inactivated position. Retighten the set screw and
move the hand lever until a reading of 5 volts DC is obtained
on the digital multimeter. Keeping the hand lever in the 5 volt
DC position, fully loosen the set screw, allow the hand lever
to return to its inactivated position, and retighten the set
screw.
The double axis boom/swing handle is adjusted in the same
manner but involves loosening and tightening two socket set
screws on the gear collar instead of the slotted set screw on
the single axis controller.
Item Description Item Description
1 Neutral (snap) switch 5 Terminal C center
2 Jumper connection (N/O) 6 Potentiometer
3 Ground terminal R 7 Socket set screw (1 of 2)
4 Slotted set screw
2
1
3
7
Single Axis
Controller
Double Axis
Controller
AA318
FIGURE 10-10
5
4
5
AA318
6
3
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