Low volume output from subwoofer

[Emilf]

I've got a KLH ASW12-200b subwoofer that turns on and outputs sound but at a really low volume. I have to max my bass, treble and subwoofer levels in my AV receiver as well as putting the gain to max to get any useful sound out of it.

I have checked the RCA plugs and they seem fine. But I noticed that some capacitors on the control and power boards seem to be leaking? I'm a newbie when it comes to these types of things so I would appreciate some input from you guys on the best course of action to fix it up.

Below I have attached pictures of the caps that I believe are damaged.

[Andrew F. Ali]

Re: Low volume output from subwoofer

That stuff around the caps is glue or sometimes silicon used to hold the caps in place during manufacture. I would troubleshoot in this order:
1. Clean the boards free of dust and other debris that may have accumulated.
2. Look for loose connections and cold solder joints on the board traces.
3. Look for resistors that may have burn spots, especially the 1W-3W sizes.
4. Look for bac caps. Do ESR test.
5. Power up and connect signal.
6. Check Output IC/Trasistors for overheeating.
7. Verify gain control is working.
8. Check the speaker for increased impedence or loose 'pigtail' wires to the Voice coils.
Hope this helps.
AFA

[budm]

Re: Low volume output from subwoofer

Can you take the pictures that will show all the board, also the pictures of the panel that shows the inputs and the controls?

[Emilf]

Re: Low volume output from subwoofer

Will do that as soon as I get home. Thanks for the input guys.

[Emilf]

Re: Low volume output from subwoofer

Also when I turn it on it flutters for a little bit before settling down.

[budm]

Re: Low volume output from subwoofer

One thing I see are those bad brown glue that will eat away the wires and copper traces, they also become conductive. They should be removed.
You can also see here what bad glue can do to the boards.
https://www.badcaps.net/forum/showthread.php?t=34692

[Emilf]

Re: Low volume output from subwoofer

Under the bigger capacitors is that also glue that should be removed? Also whats the best way to remove the glue?

[budm]

Re: Low volume output from subwoofer

Glue on the big caps, by the grey ribbon cable, etc. I use Alcohol to soften them first then scrape them off.

[Emilf]

Re: Low volume output from subwoofer

Here are some more pictures. I noticed on the back of the PCB that the soldering seems to be sloppy on some points. Some resistors or capacitors seem to be solder together on the + and - wires. It's noticeable in the upper right corner on the first 2 pictures, is this something I need to worry about?

I also scrapped away most of the glue and it changed nothing.

I also noticed that the woofer cone seems to flutter a little when I move the Gain dial.

[budm]

Re: Low volume output from subwoofer

It does not look like it will be easy to trace out the connection, I usually trace the circuit back from the power amp input circuit back to the input front end.