CH1 of Picture Pin 21
Pressed
RMS voltage
0.7 ~ 0.9 V
0.7 ~ 0.9 V
CH2 of Picture Pin 21
Keyout
Normal
5 V
0 V
Keyin
7 Troubleshooting
7-22
CHA42*7L/5**7L
7-2-18 Key Check
1) Key Map
R241
R242
R243
R244
R245
R246
R247
SW204
(V-Size)
SW203
(H-Size)
SW202
(V-Posi)
SW201
(H-Posi)
SW208
(Cont)
SW207
(Brit)
SW206
(Trap)
SW209
(Up)
SW210
(Down)
SW205
(S-Pin)
Keyout3
(#5)
Keyout2
(#4)
Keyout1
(#3)
Keyin4
(#39)
Keyin3
(#40)
Keyin2
(#42)
Keyin1
(#1)
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.
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
21
5.44 V (IC203, Keyin)
CH1 P-P = 5.44 V
CH1 RMS = 1.436 V
Summary of Contents for CHA4217L
Page 2: ...Samsung Electronics Co Ltd August 1998 Printed in Korea Code No BH68 61127A ...
Page 10: ...Memo 3 Product Specifications 3 4 CHA42 7L 5 7L ...
Page 14: ...5 Disassembly and Reassembly 5 2 CHA42 7L 5 7L Memo ...
Page 62: ...9 Electrical Parts List 9 14 CHA42 7L 5 7L Memo ...