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Disassembly & Troubleshooting Instructions
NHX–4N
Display or keyboard fault
Display or keypad fault
Lights OK ?
OK
Display does'nt work
OK
Check pins
Pin 33 V5OUT ~–6.5 V
Pin 38 VCI ~3.3V
OK
Check pin
Pin 31 V5 ~–5.0V
OK
Check;
Display foil solder joints;
D100/40/LCDRES 3.3V
Page 12
FAIL
D201/29 LIGHTS
line at + V with
lights on
OK
Check operation of
switches V43 and V45
KEYBOARD
FAULT
Pulses to 3.3V
on COL0–4 lines at
~50 ms intervals
OK
ROW0–2 lines are to carry 3.3V
and pulses to 0 V at ~50 ms
intervals when corresponding
key depressed
clock signals
FAIL
Pin 37 C1+ 3.3V/7.2kHz
Pin 35 C2+ 6.6V/7.2kHz
OK
Check soldered joints of D100
FAIL
Check R901–904 and C902, C903
Technical Documentation
FAIL
Check load in lights line
(R920, R921, R922, R923, R924)
FAIL
Check COL0–4 lines from
keyboard to D201
FAIL
Check components;
– C900, C901
Original, 01/98
PAMS
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