# Home Stereo Subwoofer, burnt component.

#### Hawkeyez

Joined Jul 31, 2022
7
REEL ACOUSTICS RSW-12. Started making a fast knocking noise out of the blue, unplugged rca cable, no change, had to unplug it from outlet. Plugged into another outlet in garage, no sound, took it apart one ground looked loose from the power supply so I tightened it, looked at the board couldn’t see anything, plugged it in, same noise. Took it back apart looked more closely and found this burnt.

The blade connectors go to the speaker, just below the resistors is what you’re looking at. It looked burnt but hard to tell, so while it was unplugged I took a very small screwdriver and touched it and it just crumbled, I scratched at it a little bit to see if there was still anything between but nothing, it’s all gone.

What I’m wondering is what is it? Could it be the cause of the repeated knocking sound and how am I supposed to know what to try replacing it with when there’s nothing left of it and I can’t find a schematic anywhere online? Any thoughts, suggestions or help appreciated.

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#### Irving

Joined Jan 30, 2016
3,132
Can you lift the burnt bits away and carefully clean the PCB underneath with some IPA or window cleaner on a cotton bud to see what it says - that may give a clue!

#### Hawkeyez

Joined Jul 31, 2022
7
I peeled it up, it’s really hard to tell but all I can see on the board is it says C24. I can only see the C and the 4, the 2 I’m guessing. Haha

Last edited:

Joined Jan 15, 2015
6,979
Looks like a leaking capacitor. The capacitor should have identifying markings printed on it.

Ron

#### AlbertHall

Joined Jun 4, 2014
12,157
Both the electrolytic capacitors appear to have bulging tops and to have leaked - the little one at to top and the big one at the bottom.

#### Hawkeyez

Joined Jul 31, 2022
7

#### Hawkeyez

Joined Jul 31, 2022
7
Ok so here’s one thing I did that may have caused that? Maybe you can confirm? After plugging it in and it made the sound again, I unplugged it, pulled a speaker wire off and plugged it backed in to see if it would still make the sound, it didn’t. So I unplugged it. Now I’m wondering if I could have caused that thing to burn up. I didn’t see a flash or smell smoke.

the reason I ask is awhile ago, it started having a faint humming sound. I just quit using it. I moved, plugged it in and didn’t hear the noise but the house is a bit “louder” with furnace and fans and fish tank. My stereo has tower speakers with 2x12” woofers so hen I have used the stereo it’s usually kind of difficult to tell if the sub is on, unless it’s a movie with some seriously low bass. It was just the other day it started knocking and getting louder and louder.

Anyway I appreciate the help, I wasnt thinking when pulling one speaker wire off that it could do damage or not. Still don’t know.

#### Irving

Joined Jan 30, 2016
3,132
Running a class D (i guess this is since its 'digital') amp with no load could generate some high voltages/currents and could have fried C24, esp if it was already compromised. In theory the amp should protect itself but if there's a fault elsewhere that could prove fatal. If there's no output load the power supply has to absorb the output power and if the PSU was already compromised through leaky caps, well ....

Chances are we'll never know, but my gut feel on this is to cut your losses...

edit: Humming is often a sure sign of a dying power line decoupling/smoothing capacitor...

#### Hawkeyez

Joined Jul 31, 2022
7
Thank you very much, yeah I don’t really know much about this stuff, maybe I’ll just put it back together, keep using it to set my stereo receiver on and watch for a deal down the road.