Trying to repair my speakers

Thread Starter

carllacan

Joined May 9, 2017
3
Hi!

I have a non-working computer speaker set lying around and I've thought I would try and repair them. I haven't got very far, so I'd appreciate suggestions.

Things I've tried so far:
- Turning up the volume (dumb, but it has to be tried)
- Connecting other device. The speakers don't work with my phone either.
- Using the audio input. There is a jack input where you can connect a microphone, or a jack-jack cable, or whatever. It doesn't work either.
- Connecting headphones to it. There is no sound in them either.

Now, here's what I know:
- The LED in the volume control box lights up, which means it is not a power issue.
- There are no blown capacitors. At least not electrolytic ones, I have no idea how to tell if the others have blown.
- There are no visibly broken elements.
- Since connecting something to the input jack port doesn't work either I think it's safe to assume that it is not the jack cable that's broken.

And here's something interesting: the jack you connect to the computer comes from a little volume control box, which is connected to the rest of the system. The headphone output port is in this box, too, so if I don't hear anything through the headphones it means the audio does not leave the control box, right? Does that mean the problem has to be in the box?
 

wayneh

Joined Sep 9, 2010
16,102
It's hard to diagnose from just your description. These are powered speakers, right? Where does the power come from? Is the amplifier circuit in the in-line box you mentioned? If you can see the circuit components, get a good photo and post it here.
 

Thread Starter

carllacan

Joined May 9, 2017
3
Thanks for your answer. I made a couple of photos.

The power cord goes to the woofer, to which the other wo speakers are connected. From the woofer a cable comes out to the control box I mentioned. In this control box there are two 3.5mm jack ports, one for input and one for output (headphones). There's also a volume knob on this box, and a jack cable comes out of it that you connect to the computer.

I didn't think you could learn much from photos of the circuit, but here they go. This is the control box (minus the casing)

And this is the circuit inside the woofer.

Let me know if you think close-ups would be helpful.
 

Dodgydave

Joined Jun 22, 2012
8,389
I would say input the audio directly to the amp pcb and also plug in your headphones to the same, bypassing the volume pcb, see if that gives out any sound, check voltages at the psu input,( top left side) otherwise you will need a working amplifier to test it with to trace the sound.

If you can take note of the chip numbers especially the long chip top left,and 5pin on the top right.
 

Thread Starter

carllacan

Joined May 9, 2017
3
I would say input the audio directly to the amp pcb and also plug in your headphones to the same, bypassing the volume pcb, see if that gives out any sound, check voltages at the psu input,( top left side) otherwise you will need a working amplifier to test it with to trace the sound.

If you can take note of the chip numbers especially the long chip top left,and 5pin on the top right.
That was a good idea! I've torn apart some old headphones and I've touched the exit pins of the volume control box and... I've instantly heard music through the speakers! I've tried several points int he circuit and I've concluded that the problem was actually in the input jack cable. Now I only need to replace it and I'll have me speakers back. I'd never done anything like this before. It feels great :)

Thank you for your help!
 
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