LS SERIES SERVICE MANUAL
ISSUE 4.0 FAULT FINDING 4
10.7 Fault Finding Charts
This section is intended as a guide to assist with fault finding. It is not possible to define every fault
condition but this information should enable the area of the fault to be easily located.
The following procedures assume that all fuses have been checked, the voltages referred to in the
voltage tables have been measured and that a RAM DUMP has been carried out.
SYMPTOM
PROBABLE CAUSES AND ACTIONS
No text on display No mains input: -
Check mains fuses and Emergency Stop switch.
Check the +5V supply to the Main PCB
Check that the console loom is connected between the
console and the 37 way connector on the rear of the
machine
Wording on LCD
display has poor
contrast.
Check setting of contrast control RV1 on the console PCB.
Minimum contrast will be with +5V on the slider of RV1 and
maximum contrast will be with 0V.
No beep when
keys are pressed
Check connections to membrane keypad: -
See figures in the microprocessor section for details of
keypad connections.
Loadcell Overload
This indicates that the output voltage from the loadcell
amplifier is out of the normal operating range, i.e. too high
or too low.
This can be caused by a damaged loadcell.
If possible, check the machine with another loadcell.
Select the Load Diagnostic Mode, disconnect the loadcell
and check the load reading on the display. If the reading
is close to zero, the loadcell may be faulty.
Check the 4V bridge supply on pin 10 of the YLC loadcell
socket on the moving crosshead.
Check the External Loadcell Loom for broken conductors.
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