Trouble Shooting; The Unit Does Not Power On; Keys Do Not Work - Polk Mono Signa S4 Service Manual

TROUBLE SHOOTING

1. The unit does not power on.

Check the [6pin cable] and confirm that it is
connected to the MAIN PCB.
Yes or no?
YES
Check that [XP2: 1,3,4pin] is about 15V.
Yes or no?
YES
Check the [20pin FFC] and confirm that it is
connected between the MAIN PCB and the KEY
PCB. Yes or no?
YES
Check that [R9] is about 5V on the KEY PCB.
Yes or no？
YES
Check that [R16] is about 5V and [R23] is about
1.8V.
Yes or no？
NO
Reconnect or use a new [6pin cable] instead.
NO
Replace the SMPS PCB.
NO
Reconnect or use a new [20pin FFC] instead.
NO
Replace the KEY PCB.
NO
Replace the MAIN PCB.

2. Keys do not work.

Check the [20pin FFC] and confirm that it is
connected to 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
Replace the old MAIN PCB with a new one so that
the EUT functions.
Yes or no？
43
NO
Reconnect or use a new [20pin FFC] instead.
YES
Replace the KEY PCB.
YES
Replace the MAIN PCB.