Bt Can Not Work; Aux In Cannot Work - Polk Mono Signa S4 Service Manual

3. BT can not work.

Check the [20pin FFC] and confirm that it is
connected to the MAIN PCB.
Yes or no?
YES
Check that [R208] is about 3.84V on the MAIN PCB.
Yes or no？
YES
Replace the old KEY PCB with a new one so that
the EUT functions.
Yes or no？
NO
Reconnect or use a new [20pin FFC] instead.
NO
Replace the MAIN PCB.
NO
Replace the KEY PCB.

4. AUX IN cannot work.

Check the AUX connector [P1] is effective on the
MAIN PCB.
Yes or no？
YES
Check that [FB3] is about 3.3V on the MAIN PCB.
Yes or no？
YES
Replace the [U8].
44
NO
Replace the AUX connector.
NO
Replace the MAIN PCB.