Thread: Discussion Troubleshooting my Dead PSU
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Old Aug 09, 2012, 07:25 PM
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Enschede, Netherlands
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The first big transformer is only used to change the "power factor" of the powersupply.
It means power input is smooth out to not overload your AC-mains. Capacitive loads like this PSU tend to draw a lot of amps from the power-line when the AC sine wave has not reached full voltage yet. This inductor makes the PSU draw most of its energy from the net at the peak voltage, thus reducing amp draw at for same watts used by the PSU. Makes your powerlines heat up less.

It does not alter the voltage from the mains to the circuit board. In fact this unit should run fine without it, but regulations make it needed.

By the way, be careful handling an exposed switching supply. Some designs keep a very high voltage on the capacitors for a long time after power is disconnected. Dont get killed out there!
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