Test F: The Subwoofer Is Inoperative

PINPOINT TEST F: THE SUBWOOFER IS INOPERATIVE

F1:

F2-F4:

F4-F6:

F6-F9:

F9-F12:

F12-F13:

F13-F14:

F14-F15:

F15-F16:

F16-F18:

F18-F19:

F19-F20:

F20-F22:

Normal Operation
The subwoofers are powered from a separate subwoofer amplifier for each subwoofer speaker. The enable/clip circuits, 173 (DG/VT), for the 2 front subwoofer amplifiers, and 174 (GY/BK), for the 4 rear subwoofer amplifiers, carries out 2 functions; to turn on the subwoofer amplifiers, and to indicate to the audio unit when the subwoofer output distortion signal reaches a damaging level. The audio unit then reduces the audio output signal to the subwoofer amplifiers. The 2 front subwoofer amplifiers receive power on circuit 829 (WH/VT). The 2 LH rear subwoofer amplifiers receive power on circuit 828 (VT/LB) and the 2 RH rear subwoofer amplifiers receive power on circuit 830 (PK/YE). The 2 front subwoofer amplifiers share a common ground through circuit 1204 (BK/OG). The 4 rear subwoofer amplifiers also share a common ground through circuit 1204 (BK/OG).

Possible Causes
- circuit 173 (DG/VT) open or short to ground
- circuit 174 (GY/BK) open or short to ground
- circuit 829 (WH/VT) open
- circuit 828 (VT/LB) open
- circuit 830 (PK/YE) open
- circuit 1204 (BK/OG) open
- subwoofer amplifier
- subwoofer
- audio unit