Modifing on a power supply should only be done by experts. There are voltages up to 325 V DC inside the power supply unit. This is dangerous!!!
The iRobot Fast Charger is basically a switched power supply for a supply voltage range from 85V~ to 250V~. This would allow to use it in the US and in Europe, beside the power cord of course.
But there is one capacitor that restricts it for use with up to 135V~. It is no problem to change it, there is even enough space in the case.
First step is to remove the rubber base on the bottom of the power supply. Underneath there are four screws to remove for open up the case. The PCB is fasten with one additional screw.
1. The capacitor (marked with a '1' in the picture above) has a capacity of 47µF and an electrical strength of 200V which is to low for switched power supply used with an supply voltage of 230V. It is necessary to replace it with a capacitor with an electrical strength of at least 385V (most of the time a 400V type is used). If possible, a type for a temperature range of 105°C should be used (lifetime). If a 47µF type is not available, a other value of at least 22µF can be used.
Attention: When replacing the capacitor take care of the correct polarity!
2. The power cord (marked with a '2' in the picture above)) should be replaced with a power cord of the used type. Alternatively, the plug itself can be replaced.
When assembling the power supply, take care of the position of the LED and the pull relief of the power cord.
The last step is to check the power supply output voltage of 22V DC.
Harald send me a picture of his Roomba Scheduler power-supply. There is an additonal varistor (3) on supply-entrance. This varister is an overvoltage-protection and should be replaced with an approporate type, like the EPCOS "S14K250". It is also possible to only remove the varistor but then the power-supply is no longer overvoltage-protected. In any case the 120V varistor must be removed because the operation at 220V supply voltage would destroy it immediatly and may cause permanent damage to the power-supply.
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