Sam4s ER-420F - Block Diagram; ER-420 M Block Diagram

8 Troubleshooting
SAM4S ER-420M/F SERIES 8-5
End
Key Board Problem
Key Input
Failure ?
Y
N
1. Check the Key Scan Part 74HC138(U27)
2. Check the Key Return Part 74HCT541(U2)
3. Check the related Circuit and Pattern
4. Check & Change Key Board Assy
5. Check the KBD Connector on PBA
Specific Key
Failure?
1. Check the affected Key
2. Check the Matrix Bus & Data Bus
3. Check the Diodes(D22~D29)
4. Check the Key Board Assy
N
Mode Key
Ok?
Y
Y
1. Check the Harness & Mode Key Assy
2. Check Diode (D18)
3. Check the 74HCT541 & Data Bus & CPU P10.3
N
8-5 Key Board Problem