I have an Altec Lansing speaker system ( model MX5021), that quit working. Does anyone know where I could get a schematic for the board or possibly purchase a new board. There seems to be power on the board as I have measured the output from what appears to be voltage regulators. I am getting a positive voltage out from one of the regulators and a negative voltage from the other. They both are approx. 9 volts. I can hear a faint hum form the speaks and when measuring the voltage regulators I hear what appears to be a little hum when I touch the meter lead to the regulator. I don't see any visible signs of damaged caps or any other components on the board. Any help would be appreciated.

Thank you

 

Have you contacted Altec Lansing?

 

Chances are good that they want you to buy a whole new unit. Are you up for that?
For example:
New unit $49.95
Replacement board $169.95

 

Have you contacted Altec Lansing?

Yes I have and they said they do not support this unit any longer.

 

Can you try tracing the signal from the input to the output with a multimeter set to AC?

The simplest solution is probably to remove the old amp and buy a new small amplifier with stereo and subwoofer outputs to power the speakers.

 

Can you try tracing the signal from the input to the output with a multimeter set to AC?

The simplest solution is probably to remove the old amp and buy a new small amplifier with stereo and subwoofer outputs to power the speakers.

I thought about saving the speakers themselves, but not sure of the impedance and the thing I really liked about the unit is it has a remote control for on/off and volume control. As for tracing the signal I have not tried that, but without a schematic that can get to be a daunting task. The board has two IC's that are heat sinked and most likely are right and left channel amps, which I thought about replacing since they are not to costly, but since I have no out put from either channel I thought it seemed like something common to both is more likely. I guess both amp IC's could have blown out. With out a schematic I have no idea if my voltages are correct or what some of the board mounted IC's are.

 

You can measure the speaker resistance with an ohmmeter. The resistance is usually an ohm or two less than its impedance rating.

You could power it with an small receiver that has a remote.