Replace Subwoofer Capacitors in 7 Easy Steps

Capacitors can be found in various electrical circuits and motherboards of electronic appliances including subwoofers and speakers.

They reserve some amount of electrical charge as an instant power available for the subwoofer amp and are typically placed in the amp’s circuit.

Over time the elements inside the capacitors can melt or turn faulty and will need a replacement.

Let us understand why the capacitor wears out along with symptoms of a problematic capacitor and the replacement steps.

How do capacitors wear out?

Aging is the most common factor for Capacitors to wear out and lose the ability to perform their job.

Over time, the elements inside the capacitors such as electrolyte, paper, and aluminum foil will show signs of degrading physically and chemically.

Additionally, it can deteriorate prematurely due to excessive heat or current, high-resistance, capacitance drift, high dissipation factor, or low insulation resistance.

In such instances replacing the subwoofer capacitors becomes necessary.

How do you know your subwoofer capacitor is bad?

There can be many symptoms of a bad capacitor in a subwoofer amp such as overheating can cause melting.

This will further result in warm air blowing out of your amp’s circuit.

You can also notice a burning smell coming off the amp or experience a humming noise from subs.

Other signs of a bad Subwoofer capacitor

  • A faulty capacitor will have a Swollen shape.
  • The top of a bad capacitor will be bulged or cracked.
  • It will have a misshapen base.
  • Signs of Fluid leakage.
  • Rust coloration can be noticed.

How do you test the subwoofer capacitor?

One of the best ways to test the capacitor of your subwoofer is by using a multimeter.

Touch the meter leads (terminals) red to positive lead and black to negative lead.

You can refer to the image below for your reference.

testing the capacitor

Usually, the meter reading starts from zero and then moves slowly toward infinity.

You can either test the capacitor after removing it from the circuit or simply test it while it is fixed to its assembly.

How to replace the subwoofer capacitor?

Replacing capacitors from the subwoofer’s amp circuit can be done at home using the right tools and little bit of technical knowledge.

Let us look into the step-by-step instructions to replace subwoofer capacitors.

Things to remember

  • You should get a suitable or the right type of capacitor for your amplifier’s circuit.
  • Some Subwoofers amplifiers include multiple capacitors, you should identify the right one that needs replacement.

Step 1: Disconnect the subwoofer from power

The first step is to disconnect the subwoofer and speaker from power to prevent electrocution.

Additionally, make sure to disconnect the speaker wires and cables to ease the process.

Step 2: Unmount the amplifier from the enclosure

For active subwoofers and speakers, you will need to unmount the amplifier from its enclosure.

This panel is typically available at the back of the unit. You can refer to the image below for your reference.

back panel of subwoofer

In the above image, the screws that secure the circuit panel are highlighted with yellow circles.

It is common in most subwoofers and speakers, the amplifier panels are typically mounted to the units with the screws secured on the outer edges.

The panel has the wiring slots and other settings on the outer side and the circuit board faces inside the enclosure.

Once the frame is unmounted you will be able to see the capacitors on the board.

Refer to the image below for your reference.

capacitor on board

Additionally, if you have a passive subwoofer, then you will have to unmount the circuit from the external amplifier to access the capacitors.

Step 3: Determining the faulty capacitor 

A faulty capacitor can be difficult to determine, as it can be smaller in size in some cases.

Since it can be visually difficult to identify at times most people use a magnifying glass or an eye loupe.

Most defective capacitors will appear swollen or bulged and closer inspection will help determine the faulty ones.

Additionally, most capacitors filled with conductive liquid electrolytes can be determined through leaks.

Note: Some amplifier circuits will have multiple capacitors and the setup will look complex for you.

As seen in the image below.

complex capacitors

Hence do not proceed if you are not confident enough, instead consult a service professional.

However, with a little knowledge, you can try to determine and test the faulty capacitor.

Step 4: Test the old capacitor

You can either remove the capacitor for testing or do it on board.

We have discussed the same in the article above.

Note: You may or may not replace all the available capacitors if other caps seem to likely fail in the future.

Step 5: Desolder old capacitor

Once the faulty capacitor is found it is time to desolder and replace it.

Typically, soldered capacitors on circuit boards need to be desoldered.

Remove the old solder (layer) from the circuit board with a Soldering Iron.

As soon as the hot leads of the soldering iron come in contact with the old layer on board, it liquifies and you are free to remove it.

Make sure to do it carefully and without damaging the circuit board.

Clean or wipe the surface with a soft and clean cloth before mounting the replacement capacitor.

Step 6: Mounting the replacement capacitor

Place the replacement capacitor into its assembly and push the thin wires to its place for soldering.

Make sure to place the leads properly in their existing slots or place them like the old capacitor.

If the subwoofer’s capacitor has long enough leads exposed on the front side of the amp’s circuit board, you can cut the capacitor off leaving the old leads.

This will allow you to solder the replacement capacitor to existing leads.

You can use a soldering machine or soldering iron to firmly fix the leads to the terminals on the amp’s circuit board.

Make sure to firmly solder the new capacitor to prevent it from moving or shaking during vibrations.

You can refer to the image below as a reference to using soldering iron.

using soldering iron

The soldering typically cools down quickly, however, you should allow some time to let it cool and settle.

Step 7: Mount the circuit back for testing

Carefully, mount everything back to its places such as the circuit board to its assembly.

Reconnect the sound system wires and power on the subwoofer.

Play a test music to check if everything is working like before.

Final Thoughts

Replacing subwoofer capacitors can be done at home using basic hardware tools, soldering iron, and the right replacement capacitor.

Circuit boards employing multiple capacitors can confuse you, hence you will need to be very careful in determining the faulty ones.

Most capacitors last as long as your sound systems or subwoofers do, however, using them improperly can lead to pre-mature wearouts.

If you have any confusions or if you are not confident enough in the replacement process simply consult a service professional for help.

 

Armed with a Diploma in electrical engineering and a remarkable 12 years of expertise, he excels in rejuvenating music systems, washing machines, dryers, and laundry-related appliances. Manish's profound insights and practical know-how establish him as a credible authority in appliance and music system repairs. Contact: manish.singh (at) subwooferblog.com. He's always ready to lend a helping hand!