I recently found some awesome altec lansing speakers with a huge sub too. but ... i can't find the volume control knob and without that, i can't make it work !! T___T any solutions? i tried looking for it online but couldn't find a spare one for sale anywhere! :S

Checkout:
https://www.manualslib.com/manual/365959/Altec-Lansing-Vs4121.html

I suggest you to see this:
Altec Lansing Amplified Computer Speaker Repair

I have the same problem I tested the power volume controller with in my friend sub-woofer and same issue, is not the sub-woofer neither the speaker, is the power volume controller definitively.

theres no on/off button for the subwoofer. once you plugged in the power cable,turn on the speaker system by turning the VOLUME knob on the right satellite until you hear a click sound.
An LED will light on the front of the right satellite when the power is ON. if you still dont hear any sound from the sub woofer then check to make sure that all cables are connected properly and are making a clear connection.

hope this help

The problem I have found is the contact glue between the back panel and circuit board inside the sub woofer. The glue becomes conductive after some time (2 years..!!) and needs to be scraped away from across tracks, you can tell the problem areas as the glue is pale yellow but goes brown and conductive over time. Good luck.
Regards
aj

Dell (Altec Lansing) A425 Subwoofer Pinouts

This is a standard female DB-9 serial port.
Here are the pinouts.

Pin 1 = Left Speaker Out +

Pin 2 = Left Speaker Out - (Common Ground)

Pin 3 = Left Line In +

Pin 4 = Right Line In +

Pin 5 = Left/Right line In - (Common Ground)

Pin 6 = Right Speaker Out +

Pin 7 = Right Speaker Out - (Common Ground)

Pin 8 = Power A

Pin 9 = Power B

Jumper (short) Power A to B to turn on.
If you want a volume control you need to put one on the inputs. You will buy buy a stereo volume control or potentiometer.
Here is some info on how to do this.
http://g4tv.com/screensavers/features/43665/Pump-Up-The-Volume.html

Cheers!

jjohnmith

First things first:
1) check your speaker for good connector, and all is working is playing fine.
2) check if your warranty covers one SPK. or RMS
other than that ,
Good Luck

if you are a technically skilled person
simply clean all the IC(chip) leads, by using a blower or using a painting small brush
the dust come in contact with the other pins that make this problem

I am also experiencing the same problem as yours...