Technics SU-G700E - 7.17 No Audio Output from PRE OUT terminal

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7.17. No Audio Output from PRE OUT terminal
7.18. No LAPC Function
No audio output from PRE OUT terminal.
YES
Replace FFC.
NO
Is FFC between
P6503 on AMP PCB and
P4552 on Main PCB
damaged?
Replace AMP PCB.
Replace Main PCB.
Still not remedy.
No LAPC Function.
Is the correct voltage
presented at Pin 7 of P6503
on AMP PCB during LAPC operation?
Normal: around 3.3V
Is the correct voltage
presented at Pin 34 of P4552
on Main PCB during LAPC operation?
Normal: around 3.3V
YES
NO
Replace FFC.
NO
Replace Main PCB.
Is the correct voltage
presented at Pin 20 of P4551
on Main PCB during LAPC operation?
Normal: around 12V
YES
YES
Replace AMP PCB.
NO
Replace FFC.
Is the correct voltage
presented at Pin 11 of P6502
on AMP PCB during LAPC operation?
Normal: around 12V
YES
NO
Replace Main PCB.