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Failed capacitor - what else to look for

chilledpain

New Member
Hi all,

I'm new here and hoping to have some advice.

I have a B&W subwoofer with a faulty amplifier module - the capacitors are blown. (unit had no power whatsoever)

Intending to replace the capacitors and main fuse but wondering if there is anything else I should be replacing whilst I'm there? ie: the potential cause of the capacitors blowing. Please speak to me like I'm a 4 year old - I'm aware of the dangers with capacitors and how to discharge them but not so much with regards to the circuits and how they work as such.

I have attached some images of the capacitors and circuit board.

Any and all advice would be greatly appreciated.
 

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chilledpain

New Member
Hi there Fourtytwo and Diver300 - thank you for the replies. Please see below for my comments:

I am from Australia
The specs on the capacitors are 200wv 820uf 105°C (Sanwha branded)
I now know what a rectifier is (basic understanding) after a Google search :)
The model number of the subwoofer is PV1D - amplifier module number is UcD400mp V4.
Link to a datasheet on the amplifier module: https://www.scribd.com/document/471965546/UcD400MP-Datasheet-R5

I have been trying to match the capacitor specs online but haven't been able to find the Sanwha branded capacitors in the specs I need unfortunately.
 

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Diver300

Well-Known Member
Most Helpful Member
You can use any brand of capacitor. You will need the same pin spacing and diameter. You may be able to use longer capacitors if you have space.

The voltage rating and temperature rating should be the same or larger. The capacitance can be larger as well. In that application, the bigger the better.

The item D2 is the bridge rectifier. The two centre pins are connected to the mains (via noise filters and a fuse) and the two outer pins charge the capacitors.

The two capacitors are in series. That is done so that they can be charged in series with 240 V mains and separately with 120 V mains, giving the same voltage across the two capacitors for either supply voltage, as long as the selector switch is in the right place. The damage shown could simply be that the switch was set wrong once.

There should be a pair of balancing resistors, one in parallel with each capacitor. It's worth checking that those are working. If not, you will get a bigger voltage on one and then it will fail.
 

chilledpain

New Member
Thank you very much for the reply Diver300 - you have been super helpful! :) Will get to checking the resistors before installing the replacement capacitors.
 

fourtytwo

Active Member
Beware, this unit has automatic voltage selection and it is possible the capacitor has failed due to a fault in it, simply replacing the capacitors will cause the same failure.
It is not a good idea to put any capacitors in an SMPS, they are subjected to high ripple currents so the original specification should be found and a same or better replacement found with regard to ripple current rating and esr.
 

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