My Altec Lansing VS4121 stopped working when i play my dvd. I can only hear very very faint sounds. It is totally fine when i watch tv. So obviously the speakers are not damaged. What could be the problem?
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Normally these low end system components depend on each other and cannot be interchanged with components from other system. So if one of the components (subwoofer or right control satellite speaker) breaks or gets lost the whole system is unusable... I was in the same situation. Got a subwoofer from VS4121 without original satellite speakers. I acquired satellite speakers from Altec Lansing 251 which used same connectors but the internal wiring was different and incompatible. Speakers are also glued together so it is impossible to open without damaging it. Obviously there is no service documentation anywhere.. But if you like electronics you can try to make something based on the information below:
Altec Lansing VS4121 connector pinout: Take the male connector (from right satellite speaker) and number pins in first row from left to right as 1-3, pins in the second row as 4-7, pins in the bottom row as 8-9 and the circle enclosure as 0. Then: 0 - Ground 1 - Speaker Right 2 - Treble (seems just like voltage control but may need to be confirmed: Min=0V; Max=voltage from Volume control Pin 9) 3 - Head Set Right 4 - Bass signal (not sure what the exact original design is as I have not opened the speaker) But seems like they use 50K potentiometer and some sort of RC low pass filter configuration. When potentiometer is set to Min it is shorted with ground. When set to Max it is taking signal from Right and Left Head Set (pins 3 and 5) combined through some larger resistors and low pass filter. 5 - Headset Left 6 - Ground for Headset (grounds 0 and 6 seems to be connected in the subwofer but within the right satellite speaker they seem to be isolated with separate leads to sub) 7 - Power ON/OFF. When OFF or headset jack plugged then 0V. When ON and headset jack unplugged then 5V 8 - 5V Power in 9 - Volume (min=0V; max=5V). It seems they use 50K potentiometer but probably anything >10k should work.
At minimum for standalone subwoofer you will need to implement: - Power On/Off (switch between pins 8,7) - Volume control 50k potentiometer (probably anything between 10k and 50k will do) between pin 7 and 0 with variable output to pin 9 - Bass control - join two resistors R (I used 7k) and call this join point A. Attach other ends of the resistors to pins 3 and 5 respectively. Attach 50k potentiometer (I used 10k) between point A and ground 0. Attach Variable pin of the potentiometer to pin 4 (Bass input signal). Attach capacitor C between Pin 4 and Ground pin 0 (I used Electrolytic 1uF with negative end to ground) . Resistor R and capacitor C should make simple passive low pass filter (Google for formula) that should short any frequency higher than 80-120Hz to ground and feed frequencies lower than 80-120Hz to pin 4.
PS: I managed to hack 251 control satellite speaker to somewhat work with VS4121 Subwoofer but that is another subject. All electronic parts were salvaged from old broken TV so total cost was $0 but took several days of tinkering for speakers that I could buy used for $10-20 :)
The reason for the hum in the Altec Lansing VS4121 speaker system is the stray field of the power supply transformer. This stray field is strong enough to affect the amplifier. All other reasons given by numerous reports on the web do not apply. If you are handy and have got the time you may mitigate the problem by physically moving the amp away from the power supply or turning it 90 degrees. I managed to lift up the amp in my subwoofer by about 50 mm, which was difficult to achieve and did not cure the problem perfectly. I don't see any other way to solve this problem except you feed DC in from the outside and do not use the internal power supply. That would be really odd indeed
If the speakers are brand new it makes me wonder how you know they worked fine in the States? I am also wondering how they were transported due to them probably being intolerant to extremes of temperature/humidity and probably vibration.
I am also wondering if you are using the correct supply voltage and type of supply.
If you are using the power adaptor supplied for use in the USA, it would probably be incompatible with your supply even though you are using a transformer.
If you are certain the speakers are in good order I suggest you obtain a power adaptor designed for your 220 volt 50Hz supply. I have browsed a little and cannot find a note of the power requirements for the integrated amplifier but this is presumably marked on the adaptor, the speaker or in the manual and so the power adaptor could be checked on and off load with a suitable voltmeter. I would be surprised to learn the supply is adequate