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KX-T2388
4) How to check the key scan I/O (IC1)
Connecto to the telephone
line and lift the handset.
Does the signal at pin
23 of IC1 480 kHz
oscillate?
WWW
Is the voltage at pin 5, 6
and 26~29 of IC1?
Tee:
---0V
YES
Is the voltage at pin
|NO
Check D5~D8
30 of IC1 4~5 V?
D24 and R27.
Is the voltage at
pin 24 of IC1 high
logic level?
NO
Check Q5,
R25 and R26.
Is the voltage at
pin 25 of IC1 high
logic level?
Check IC1.
NO
Check Q4, D7
and R23.
Check the contact
of Key.
Is there voltage output
from any of the pins 17 to
20 of IC1 when any key is
pressed as shown below?
----4
US Ui G5
When the signals are output from
more than one pin of 17 to 20 of IC1.
Check the solder pin
17~20 of IC1 and all
keys.
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