Sony Xperia TX LT29i Working Instructions page 91

Problem Areas: Keys
3. If the key on/off switch, the BtB connector or the FPC of
the RCV Flex FPC is damaged – replace the RCV Flex
FPC.
4. Replace board.
1266-5087 Rev 1
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Sony Mobile Communications AB – Company Internal
Troubleshooting Guide (mech)
9(57)