Comparing two capacitors of same value but different size & colour

Thread Starter

brianWreaves

Joined Sep 16, 2021
7
Hello all,
New to the forum and happy I found it!

I'm attempting to repair a noise coming from the wireless subwoofer in my Klipsch SB3 soundbar. I posted a video of the squeal and then oscillating rumble. It doesn't start when powering up, it starts after the soundbar and subwoofer connect wirelessly.

Initially I suspected the issue was capacitors on the subwoofer's internal power supply or amp but I didn't find anything obvious. I disassembled the soundbar and found a bulging 470uF 25V cap on the circuit board with burnt glue that obviously needs to be replaced.
klipsch_sb3_210916_bar_capacitors_02.jpg

I believe it's part of the amplifier's output since there are two of them and the soundbar's speaker connections are pretty close (On the left), but I'm not certain. I'm only hoping this will fix the subwoofer noise but the wireless module for the subwoofer (On the right) is on the other end.
klipsch_sb3_210916_bar_mainboard_01.jpg

I have a capacitor with the same rating but as you can see in the photo it's much smaller and the skin is a different colour. (Capacitor in photo is not bulging but was also in burnt glue so I'll replace it, too)
klipsch_sb3_210916_bar_capacitors_01.jpg

My question, does the replacement need to be physically identical or is it safe to use the one I have with the same values?

Thanks for reading!
 

MrChips

Joined Oct 2, 2009
24,398
Welcome to AAC!

Physical dimensions may vary with manufacturing techniques and advances in materials. Once you match the capacitance and voltage rating, the other things to watch for are ESR and temperature rating.

I think what you have will be fine. All bulging capacitors must be replaced.
Generally speaking, it does not hurt to move up to the next higher voltage rating.
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
7
I created a new problem. While working on the board I was scraping off the yellow component glue and scrapped off a tiny cap; I was trying not to do it and did it anyway! Actually it broke off and obviously I have no idea what value is meant to be there. It's not labelled and would be too small to read if it was labelled.

In this photo you can see what I scrapped off and where it was located.
klipsch_sb3_210917_bar_capacitors_01b.jpg

My guess is it is needed and not there just for decoration. Without a schematic I won't what to replace it with.

Any suggestions on how I can find a schematic or repair this?
Any suggestions on how to better remove this glue?
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
7
Thank you both for chiming in!

I can‘t see the cap from that photo but it may be possible to replace it if any of the pads remain.

You don’t have to remove the glue.
The cap is the small brown rectangle below the board I drew the arrow from.

I was removing the glue as I understood it can cause problems with circuits as the glue ages. Is this on longer the case?

Try a 100nF ceramic chip capacitor for starters.
How will I know if the cap is/isn't the correct value?
 

MrChips

Joined Oct 2, 2009
24,398
There are not too many places in digital circuitry where capacitors are needed. The most common value is 100nF for power supply decoupling.

First try the board without the capacitor. Then add the capacitor. You will not notice any difference if it is used for power supply decoupling.
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
7
Welllll, damn! That didn't work and I haven't been able to find an electronics repair shop willing to tackle this issue. I guess I'll disconnect all the internal and connect to an external amp.

Thanks for all the input.
 
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