Nokia NHM-4 Series Assembly, Disassembly And Troubleshooting Instructions page 54

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Keypad troubleshooting 1
Keypad
faults
Is the power key OK ?
Yes
Keypad
faults 2
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Measure voltage
No
from S302
Is it HIGH ?
Measure voltage
from S300 when
power key is pressed.
Is it HIGH ?
No
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No
Yes
Yes
Change S302
Phone is
jammed
Check R301,
C312, S302
and line.
If OK –>
Change UEM
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