Capacitor Help

Thread Starter

johnr9q

Joined Jan 31, 2024
3
My Definitive Technology Subwoofer developed a loud hum. I looked online and saw that replacing the capacitors might fix it. My capacitors are not budging which, I understand, can indicate they are bad. There is no voltage written on the capacitors. The only thing written on them is: Bennic, Bi-Polar, 220 mfd, Vent, -40c + 85c. Can anyone help me find a replacement?
 

KeithWalker

Joined Jul 10, 2017
3,147
You don't mention a model number. Does the speaker have a built-in amplifier?
The bi-polar capacitors will be in the low-pass filter circuit. Replacing them will not get rid of hum.
 

KeithWalker

Joined Jul 10, 2017
3,147
The 15TL has a built in 500W amplifier. I guess that this one is five to eight years old. Electrolytic capacitors do dry out with age, so they are the most likely suspects and can cause hum. The capacitors in the power supply are the most likely ones, but any de-coupling capacitor in the amplifier could also be suspect.
If the capacitors are not bulging at the ends, look for leakage of the electrolyte on the circuit board around the base. If there are no clues, try replacing them a few at a time, starting with the highest capacitance values. Make sure you replace the capacitors with ones having the same or higher working voltage.
Note the polarity! If you put one in the wrong way round, you could quickly destroy the amplifier
 

ApacheKid

Joined Jan 12, 2015
1,658
My Definitive Technology Subwoofer developed a loud hum. I looked online and saw that replacing the capacitors might fix it. My capacitors are not budging which, I understand, can indicate they are bad. There is no voltage written on the capacitors. The only thing written on them is: Bennic, Bi-Polar, 220 mfd, Vent, -40c + 85c. Can anyone help me find a replacement?
What does this mean "My capacitors are not budging" ? How about a photograph or two? Swap the two speakers around, prove that it is the speaker and not the amplifier.
 
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