Here on my table the DB500 DreamBox baby 
He will not start; frontled is not green.
How I fixed this and my analysis below.
The adapter provides 12 volts unloaded.
But charged with a 22 Ohm resistor it drops to 3 volts
Even charge 10 Ohm to 1.7 volts.
With appropriate force (with the hammer) on the bond line I onened the casing
My suspicion is that the feedback-circuit does function correctly.
The feedback from secondary side is realised with an opto-coupler to the primary side. This signal is a pulse, which is flattened using a capacitor.
So C10 removed (see photo) and measured after .... 0.5uF instead of 47uF.
A new one (47 uF and 25 volts at least) and the powersupply works again.
p.s. Tip / warning:
Always remove the Mainsplug before you graabed the print.
The thick (brown) capacitor on primary side might be charged with 325 volts. I always measure that elco, before I do repair. On my voltmeter probes I've placed a 47Kohm resistor. This is to discharge the elco while measuring the voltage.
