JMlab Chorus SW700S
The JMlab Chorus SW700S subwoofer is a high fidelity product sold by Focal. The amplifier modules are built by BASH, using very cheap components. I recommend replacing all electrolytic capacitors before you even begin troubleshooting.
Linear board: the bipolar 47 μF (or maybe they're 4.7 μF, I can't remember) capacitors are ALWAYS blown. On the same board there is a small JFET labeled C930AB. I have successfully replaced this with a J113.
PSU Board: replace all capacitors regardless of condition. You may also have to replace power mosfets. They are common off-the-shelf parts.
I have not managed to find a schematic of the power supply board, however the audio board (linear board) is the same (possibly different board revision, but very similar) as the PSB Speakers SS5i. That service manual can be found if you look for it.
Original article credit: AMelbye