Hi All,

I work in computer networks but been interested to learn electronics. I've an old MS50 powered amplifier subwoofer which has little weird setup of circuit.
See images below.


I've lost Satellite speakers and have sub-woofer only. As it can be seen in diagram, right speaker has the RCA input jacks and feed the input through Pin no 5 and 6 from right speaker to sub woofer amplifier IC. Pin no 7 feeds the amplified audio back to right satellite speaker. What i want to accomplish is; to install RCA female pins in the subwoofer body for Input and one female RCA for right speaker output. but i am not sure, how i can do it? can i just splice the input RCA to pins 5 and 6 and pin 4 to R channel output? but how i will feed the power +12V to amplifier? what other components needs to be installed. i've attached the technical manual to the thread which has high resolution circuit images. Any suggestions?

Thank You.

 

Yes just parallel the pins up on the new socket, the 12V comes from the din socket on the sub woofer, you can just link the pins out on the sub woofer and the power will be on continuously.

 

You have a three channel power amp. What test equipment do you have access to? Oscilloscope? DMM? Signal Generator?

 

Hi,

Thanks for the replies.
@JoeJester I've a Digital multi meter.

 

The block diagram you shown is one page before the schematic.

You have neither channel on the satellite speakers. You only have the Woofer.

Are you sure the satellite speakers are good? Have you substituted them?
Is there an output at the headphone jack? I'm sure there will be since it's before the amplifier.
Have you measured both the +12V and -12V supplies?

Attached is the power amplifiers datasheet.

 

The block diagram you shown is one page before the schematic.

You have neither channel on the satellite speakers. You only have the Woofer.

Are you sure the satellite speakers are good? Have you substituted them?
Is there an output at the headphone jack? I'm sure there will be since it's before the amplifier.
Have you measured both the +12V and -12V supplies?

Attached is the power amplifiers datasheet.

Hey Joe,

I don't have satellite speakers anymore, i've lost them somewhere. Right speaker had RCA input which used to feed the audio input to subwoofer through 8pin din connector. I've attached the technical document in my post which has schematic diagrams of both subwoofer and right speaker circuit design. which may help to explain the functionality. I want to know how to input audio directly to subwoofer while power was also coming through
170203"]Yes just parallel the pins up on the new socket, the 12V comes from the din socket on the sub woofer, you can just link the pins out on the sub woofer and the power will be on continuously.[/QUOTE]

Hi dave,

Thanks for replying. So, what i did is to cut the 8 pin din connector from 1 side. i've 8 cables now, i've already traced them. there is a mesh around the cable which i believe i can use as ground.

Pin 5 SRI (i assume its right input)
Pin 6 SLI (i assume its left input)
Pin 7 is the Right speaker + output.
Pin 1 is +12v
Pin 2 is -12v
Pin 3, Pin 8 and Right speaker negative are all ground.
Pin 4 is power input for power Amp IC.

So, should i just splice pin 5 to +ve of RCA and -ve to ground mesh and pin 6 to +ve to other RCA & -ve to the mesh. will that input work?
what about connecting power, can i connect pin 1 to the pin 4? will that work?

 

Yes to both questions.
Connect the power leads to +12v, and connect the speaker inputs L and R to pins 5,6..and common the ground terminals.