Fixing/Converting Roomba adapter from 110V to 240V for New Zealand

I recently bought a Roomba 570 robotic vacuum from ebay. The robot came with a 110V/120V adapter. Since I'm pretty used to seeing adapters that support 110V-240V, I didn't bother checking the ratings and was greeted by an alarming bang and puff of yellow smoke when the adapter was plugged into our New Zealand 240V mains.

Fixing & Converting the switch-mode adapter from 110V to 240V is relatively easy but you shouldn't attempt it unless you know what you're doing. It can be very dangerous whenever working with high-voltage devices.

Opening the white adapter casing up was relatively easy (the screws are underneath the rubber feet). The yellow smoke came from a blown 200V 47uF capacitor.

To convert the adapter to 240V, you need to replace the 47uF capacitor with a higher voltage capacitor but similar capacity capacitor. I was able to get a 450V 47uF capacitor from jarcar for under $8. I would have preferred to get a capacitor with a lower voltage rating but couldn't find any local suppliers. Because of its high voltage rating, the 450V capacitor was a bit too large to mount vertically so I had to mount it sideways. I secured the capacitor from contact with other components using some blobs of hot glue. Electrolytic capacitors are polarised so make sure you make a note of which way round the original capacitor was mounted when you mount the new one.

The only other component you need to change is the varistor which is the blue disk-like component. The varistor protects the circuit from high voltage spikes. I used this one from jarcar which was under $2.

When you've finished putting the adapter back together again, plug it in and carefully measure the DC output from the circular plug (the one that goes into the docking station). The adapter should be outputting 22.5V. You shouldn't plug the adapter into the Roomba docking station until you are sure that the adapter is properly outputting 22.5V otherwise you could damage the docking station and the Roomba if it's docked.


Now for the pictures:
















The adapter after it has been opened. The capacitor (top) and varistor (bottom left) have been circled. Notice how the capacitor has burst.

















The replacement components. A 47F 450V electrolytic capacitor and a 275V varistor.


















The original capacitor (left) and the replacement capacitor (right).

















The adapter with new capacitor and varistor in place.

















The adapter lid would not close because the 450V capacitor was too large. Here, the capacitor is mounted sideways.
















The Roomba, happily charging from his newly converted 240V adapter.