My PA300 went out for no apparent reason so I took the adapter apart and the problem was that the low-voltage output wire had broken just inside the case.
You can separate the wire from its output grommet by being very careful; chop the wire either side of the gremmet and you can get the bits out from inside. Place wire back though grommet, strip, tin, reterminat, trim cable, reassemble and everything works again.
I'm one of those people who feels naked without a toolbox and soldering iron. This problem was fixed "in the field"!
Furthjer info: Switch mode power supplies ought to be very reliable because the chips inside can auto-protect the supply under most fault conditions, so in general the issues tend to be dodgy soldering or broken wires.
However here in the UK however there are siginficant numbers of TV Satellite decoder boxes where the PSU is built to a price and the components are running close to their limits; the units are prone to sudden failure after a couple of years operation.
There are repair kits available for a number of the units, which replace existing components with higher rated alternatives.
The biggest causes of failure are burned-out resistors and dried-out electrolytic capacitors. Fix resistors by fitting a physically larger (and therefored more heat-resistant / dissipative) alternative of the same value; fix capacitors by using a higher voltage rated capacitor. The biggest stopper with this fix is getting better rated components that fit in the available space.
There might be a case to be made for replacing all capacitors in switch mode power supplies after 5 years hard use as a precautionary measure. On the other hand, if it ain't broke....
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John Allcock
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