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Subwoofer and speakers fault finding



Subwoofer operation

For the subwoofer and speakers to work, the following connections are necessary:


Wallwasher

the wallwasher PSU needs to be connected to the wallwasher and switched on.

the wallwasher needs to be switched on.

the wallwasher needs to be connected to the PC via the USB cable.

The sidelight speakers need to be connected to the wallwasher.


Subwoofer

the subwoofer needs to be connected to the mains and switched on at the mains.

the subwoofer needs to be connected to the wallwasher Audio In socket via the 7-pin mini-din cable.

the subwoofer needs to be connected to an audio source (normally the line out on a PC) via the 3.5mm green audio in jack socket on the back of the subwoofer box.


The amBX software does not need to be installed for the subwoofer / speakers to work.



INITIAL CHECKS

When doing these checks, don’t just look at a connection. It’s possible for a plug to look in place, but in fact it may be slightly out and not making contact on all pins. Manually push the plugs in or remove the plug and put it back.


Check

- the mains plug is connected to a working mains socket and the mains socket is switched on

- the mains plug fuse (if fitted) is OK.

- the 7-pin mini-din plug is fully connected to the wallwasher.


Check

- the wallwasher is switched on and working.

- the USB cable is connected between the wallwasher and the PC. If necessary, try a different USB cable.


Note

There can be problems with the wallwasher not working caused by the way the USB connection is made, especially if you are using long cables or hubs (see the USB page). It may be better to connect the wallwasher directly to a working USB socket on the PC when doing these checks.


Check

- there is sound coming from the PC on both the Left and Right channels. The best way to do this is to temporarily connect headphones to the Line Out / Audio Out socket to check (remember to put the green audio plug back in the PC afterwards).


Check

- the 3.5mm plug cable is fully connected to the green Audio In socket on the subwoofer

- the other end of the cable is connected to the PC Audio Out / Line Out socket (usually green). If necessary, try a different USB cable.



Hum

There is normally a quiet background hum from the left and right speakers when the subwoofer is on. If you can hear this hum, this proves that the relay is closed (wallwasher OK) and a mains supply is connected to the subwoofer PSU.  It may also prove that the amplifier is working OK.

Because the subwoofer speaker has a volume control, you will not hear a hum from this if the bass control is set to Min. Turn the control to Max if testing the subwoofer speaker for hum.


Hum test

- disconnect the audio cable from the PC (leave the other end of the cable connected to the subwoofer).

- touch the metal tip of the plug. Do you get a loud hum from one of the speakers? If so, it means that the amplifier is working and there’s probably working and that there is a problem with the sound coming from the PC.

If you touch the ring you should get a hum from the other speaker.


GND (sleeve)













Fig. BF1:  3.5mm jack plug connections


Only one speaker working

Make a pencil mark on the speaker so you can identify it.

Swap the speaker connections over on the wallwasher - red plug in white socket and white plug in red socket.

Test the speakers again, then go to A) or B) as appropriate.


A)

Is it the same speaker that is faulty (i.e., it doesn’t matter whether it is plugged into the red or white socket, there is still no sound coming from it)? If so, this could be due to:

- a fault with the speakerlight plug - check for bent or missing pins

- a fault with the speakerlight cable

- disconnected tag(s) to the actual speakers, although unlikely because there are two speakers connected in parallel

- both speakers in the speakerlight dud

You will need to open the speakerlight up to check inside. You can also check the cable is OK by checking that the continuity is OK between speakerlight plug pin 10 and the positive tag at the speakers and by checking the continuity between speakerlight plug 11 and the negative tag at the speakers.

- see the Speakerlight - opening and Pin-outs pages for details.



B)

If the speaker now works in the other socket, then the problem is probably related to a channel (Left or Right).


With both speakers connected to the wallwasher, try the hum test above by touching the tip then the ring. If you get a loud hum from both speakers, then the L and  R amplifier channels would appear to be OK.

Confirm that there is sound coming out of the PC on both channels.

If it is, make sure you have a good connection between the green audio in jack and the PC.


If still no sound on the one channel during the hum test, then it’s possible the fault lies with a faulty audio cable, connections between the subwoofer and the speakers, connections within the subwoofer box, or amplifier problems.


Check the jack plug on the audio lead is fully inserted into the jack socket on the back of the wallwasher.

Try a replacement audio cable between the PC and the subwoofer.

Check to make sure the 7-pin mini-din cable is fully connected to the wallwasher.

Fully connect both speakers to the wallwasher (screw the plug to the wallwasher to ensure a good connection).

Identify whether it is the Left (white) or Right (red) channel from the wallwasher that isn’t working


Using an old speaker, or headphones with the plug cut off, connect them between the relevant pins of the 7-pin mini-din plug from the subwoofer to test the output of both channels from the amplifier (see the  audio connections diagram on the Pin-outs page). Don’t let any stray strands of wire short against adjacent pins or the outer shell or the test might not work correctly.

Connect the speaker wires to pins 1 and 2 (Left channel) and listen for sound.

Connect the speaker wires to pins 3 and 4 (Right channel) and listen for sound.


If you get sound from both channels, the problem might be a faulty connection at the wallwasher - either at the VGA speaker socket (more likely) or at the 7-pin mini-din socket.


If you only get sound from one channel, then you need to check the internal connections (see below).



If no sound from either speaker after the checks:

There is normally a quiet background hum from the left and right speakers when the subwoofer is on. If you can hear this hum, this proves that the relay is closed (wallwasher OK) and a mains supply is connected to the subwoofer PSU.  It may also prove that the amplifier is working OK.


If there is a background hum from the speakers, but you don’t get a loud hum when doing the hum test above, it’s possible that the fault lies within the subwoofer box. You will need to check the internal connections.



Checking the internal connections

open the box (see the  Subwoofer-opening page)


Inside the box, check the plugs and sockets for loose connections, especially the audio connections:

Plug on the audio jack PCB on the back of the case.

3-pin audio in plug on the amplifier PCB.

7-pin connector on the amplifier PCB.


Check, by doing a continuity test, that the green audio in jack socket is OK.


See the Subwoofer Amplifier page for details of the locations and for more tests.



Subwoofer is completely dead - no hum from any speakers

(see Hum above)

- there may be a power supply problem


Does the relay click when the wallwasher is turned on and off?

YES - proves that there is a 5v supply from the wallwasher (no guarantee the relay contacts are OK)

You will need to check the relay PCB


NO - check the 7-pin mini-din cable is fully connected to the Audio IN socket on the wallwasher

If the relay still doesn’t work, test to see if there is 5vDC between holes 5 and 6 on the wallwasher Audio In socket  (see   Testing the wallwasher sockets on the Faults and Repairs / Repairs page for how to do this)

If there is 5v DC present, the relay may be faulty.

You will need to check the relay PCB


See the Subwoofer-opening and Subwoofer Relay pages