Nokia 9000i Service Manual page 277

After Sales
Technical Documentation
6.3.1 Sense Lines HI, KEYS (9:0)?
Pressing a key draws the sense line low, from idle high state, where it is
connected in the keyboard matrix. Therefore, if no key is pressed, all the
KEYS sense lines should be in a logic high state. Should this happen,
continue to 6.3.2 otherwise proceed to 6.3.1.1
6.3.1.1 R120–R129 OK?
Check the sense line pull–ups. If the resistors are OK, then proceed to
6.3.1.2 otherwise go to 6.3.1.3
6.3.1.2 CPU fault
If the pull–ups R120–R129 are OK, then it is likely that the CPU (D130) is
pulling the sense–line low. Expect a CPU fault.
6.3.1.3 Fix the Corresponding Resistor
Change the faulty resistor.
6.3.2 Drives Toggling KEYD(7:0)?
Once the keyboard test is running, it drives the keyboard drive lines from
idle high to low state one by one, one at a time. if one or more line(s)
remain fixed low or high, go to 6.3.2.1
6.3.2.1 R112–R119 OK?
The keyboard matrix is driven through the series resistors R112–R119.
Check if all the resistors are OK. If the resistors are OK, go to 6.3.1.2 if not
go to 6.3.1.3
NOTE: Resistors R112–R119 are installed only in CPU versions A3 or A5.
If A7 version of the CPU is used, the resistors are not installed. Also if the
A7 version of the CPU is used, then the value of the resistors R120–R129
is changed!
6.3.3 Do Senses Go Low if Driven and a Key Is Pressed?
Press a key in the matrix and scope the corresponding sense line. If the
drive line is driven, but the sense line remains high proceed to 6.3.3.1
otherwise go to 6.3.3.2
6.3.3.1 Check keyboard matrix
If the sense line remains high, even though it should be forced low when
driven, expect a fault on the circuit connections. Although the CPU can
force the senses high also.
6.3.3.2 CPU Fault
If the sense lines toggle according to the pressed keys on the keyboard
when they are driven, then the CPU is likely to be defective.
Original, 05/97
RAE/RAK–1N
Faultfinding/Disassembly
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