Key Board Problem - Sam4s ER-5200 Service Manual

8-5 Key Board Problem

Key Board Problem
Key Input
Failure ?
N
Specific Key
Failure?
N
Mode Key
Ok?
Y
End
SAM4S ER-5200 Series
Y
Y
N
1. Check the nCS_KEY Signal of Decoder 74HC138(U21)
2. Check the Key Scan Part 74HC138(U16,U18, U23)
3. Check the Key Return Part 74HCT541
4. Check the related Circuit and Pattern
5. Check & Change Key Board Assy
6. Check the KBD Connector on PBA
1. Check the affected Key
2. Check the Matrix Bus & Data Bus
3. Check the Diodes(D7~D27)
4. Check the Key Board Assy
1. Check the Harness & Mode Key Assy
2. Check Diode (D25)
3. Check the 74HCT541 & Data Bus
8 Troubleshooting
8-5