Just found out what the main problem is with these supplies, its not the output filter caps as many have suggested, i have a couple of these power supplies which both exhibit the same problem.
When you plug them in the power LED gently pulses up to full brightness after about 30 seconds, but any load on the PSU causes it to shut down.
This problem lies with the main transformer, the primary side pins appear to become dry-jointed, meaning it can still drive but has no return power feed or voltage reference. You will have to dig your soldering iron into the solder as the pins are covered with some sort of high temp silicone. After repairing it the PSU was able to drive a 55w car headlamp bulb with no difficulty whatsoever.
Dont mistake the PFC transformer with the main one. Theyre roughly the same size, these PSU's have a clever IC driven Power Factor correction system which sort of threw me at the beginning.
Hope this helps.
Cheers, Dave.
