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7 Troubleshooting
7-2-18 Key Check
1) Key Map
Keyout3
Keyout2
Keyout1
(#5)
(#4)
(#3)
R241
R242
2) Voltage Check of Keyin and Keyout
– Press the key what you want to check.
– At that moment, the voltage of keyin and keyout that is connected with together should be changed as follows.
Keyout
Keyin
3) LED Check
– Pressing key, LED should be blinked.
4) How to Repair?
– If only one key has a key problem, replace that key.
– But if some keys that are connected with same keyin or keyout line have problems,
check and replace PCB pattern and IC202.
WAVEFORMS
21
5.52 V (IC203, Keyout)
CH1 P-P = 5.52 V
CH1 RMS = 3.696 V
7-22
Keyin4
Keyin3
(#39)
(#40)
R243
R244
R245
SW204
SW203
SW202
(V-Size)
(H-Size)
(V-Posi)
SW208
SW207
SW206
(Cont)
(Brit)
(Trap)
SW209
SW210
(Up)
(Down)
Normal
5 V
CH1 of Picture Pin 21
0 V
CH2 of Picture Pin 21
21
5.44 V (IC203, Keyin)
CH1 P-P = 5.44 V
CH1 RMS = 1.436 V
Keyin2
Keyin1
(#42)
(#1)
R246
R247
SW201
(H-Posi)
SW205
(S-Pin)
Pressed
RMS voltage
0.7 ~ 0.9 V
0.7 ~ 0.9 V
CHA42*7L/5**7L
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