Samsung DP14LS Service Manual page 41

6 Troubleshooting
6-2-18 Key Check
1) Key Map
Keyout3 Keyout2 Keyout1
(#5) (#4) (#3)
R206 R207
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 IC201.
WAVEFORMS
21 5.52 V (IC201, Keyout)
CH1 P-P = 5.52 V CH1 RMS = 3.696 V
6-22
Keyin4 Keyin3
(#39) (#40)
R208 R209
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 (IC201, Keyin)
CH1 P-P = 5.44 V CH1 RMS = 1.436 V
Keyin2 Keyin1
(#42) (#1)
SW201
(H-Posi)
SW205
(S-Pin)
Pressed RMS voltage
0.7 ~ 0.9 V
0.7 ~ 0.9 V
DP14L*/DP15L*