With Dennis on this - 99% of such SMPS units are of a common, simple, architecture...
They run the mains through a common & differential RF filter (mainly to prevent cr*p from the SMPS getting onto the mains, not the other way round!) which is then rectified by a full wave bridge. This is then smoothed, chopped at high frequency by a PWM control chip, fed into a transformer (normally via a FET or two), the output of which is your desired voltage that tends to be half-wave rectified, then filtered (to remove RF as much as to smooth) and connected to the output lead. A second secondary winding is used to provide feedback to the SMPS PWM chip via an optocoupler - if you look at the underside of the PCB you'll see distinct HV & LV sections, often with a routed cut between them to increase safety (stops condensation bridging the gap) - the optocoupler and the transformer should be the only things bridging the HV/LV divide.
The PWM chip has a number of safety features that shut off the supply in out-of-bound conditions, such as the output getting too high.
Replace the obviously dead capacitor, but ask yourself: "Why did it go"? Before powering up, check the bridge with some low voltage AC input and see if its giving full-wave rectified DC - if not, check the bridge (or the discrete diodes if that's what's being used).
Other things to check - the single diode on the LV DC side and the caps round that - some of the better small SMPSs have a crowbar protection system that shuts off the output in emergencies - check the HV side, then the LV side. There can be input and output normal or polyswitch fuses too..
The transformer primary should be centre-tapped - check it and check the output windings too - sometimes (rarely) the xfrmr dies... if the PWM/SMPS control chip, the transformer or the optocoupler has gone AWOL, chances of fixing the supply are slim.
HTH
They run the mains through a common & differential RF filter (mainly to prevent cr*p from the SMPS getting onto the mains, not the other way round!) which is then rectified by a full wave bridge. This is then smoothed, chopped at high frequency by a PWM control chip, fed into a transformer (normally via a FET or two), the output of which is your desired voltage that tends to be half-wave rectified, then filtered (to remove RF as much as to smooth) and connected to the output lead. A second secondary winding is used to provide feedback to the SMPS PWM chip via an optocoupler - if you look at the underside of the PCB you'll see distinct HV & LV sections, often with a routed cut between them to increase safety (stops condensation bridging the gap) - the optocoupler and the transformer should be the only things bridging the HV/LV divide.
The PWM chip has a number of safety features that shut off the supply in out-of-bound conditions, such as the output getting too high.
Replace the obviously dead capacitor, but ask yourself: "Why did it go"? Before powering up, check the bridge with some low voltage AC input and see if its giving full-wave rectified DC - if not, check the bridge (or the discrete diodes if that's what's being used).
Other things to check - the single diode on the LV DC side and the caps round that - some of the better small SMPSs have a crowbar protection system that shuts off the output in emergencies - check the HV side, then the LV side. There can be input and output normal or polyswitch fuses too..
The transformer primary should be centre-tapped - check it and check the output windings too - sometimes (rarely) the xfrmr dies... if the PWM/SMPS control chip, the transformer or the optocoupler has gone AWOL, chances of fixing the supply are slim.
HTH
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