Synology DS412+ no signs of life

[mc4ren]

I bouth in eBay a faulty DS412+.
It did show no sign of any kind of life: no fan spin, no LED turning on, no sound.
I tried a nother power supply (this one has external power supply, 12 Vdc). Same result.
I used a DC power supply and saw that it was ticking when I pressed the turn on button. So there was some short circuit.
I have no thermal camera, no other way of checking themps, so I thought: why not to increase the supply voltage?
So I did, and at 18 Vdc a capacitor exploded. That's what shows the first picture.
Surprisingly, the unit now shows some life! The blue ON lights do come up, and after some 4-5 seconds they turn off again. Sometimes, randomly, the unit power ups itself, flashing the blue light and even spining the fans! But this last for about 5 seconds and turns off. There is a AO 4914 dual N-channel MOSFET below the blown capacitor. The capacitor is connected to two of its pins. Some centimeters away, there is a similar construction, in which the capacitor is 10 uF (I took it away and measured it).
There are 12V in the drain, but the gate is not changing.
I'm quite lost here, I don't know what else to check or where I can detect the problem.

[Curious.George]

Originally Posted by mc4ren

I bouth in eBay a faulty DS412+.
It did show no sign of any kind of life: no fan spin, no LED turning on, no sound.
I tried a nother power supply (this one has external power supply, 12 Vdc). Same result.
I used a DC power supply and saw that it was ticking when I pressed the turn on button. So there was some short circuit.
I have no thermal camera, no other way of checking themps, so I thought: why not to increase the supply voltage?
So I did, and at 18 Vdc a capacitor exploded. That's what shows the first picture.
Surprisingly, the unit now shows some life! The blue ON lights do come up, and after some 4-5 seconds they turn off again. Sometimes, randomly, the unit power ups itself, flashing the blue light and even spining the fans! But this last for about 5 seconds and turns off. There is a AO 4914 dual N-channel MOSFET below the blown capacitor. The capacitor is connected to two of its pins. Some centimeters away, there is a similar construction, in which the capacitor is 10 uF (I took it away and measured it).
There are 12V in the drain, but the gate is not changing.
I'm quite lost here, I don't know what else to check or where I can detect the problem.

Now you'll have to trace foils to see how far into the circuit your deliberate over-voltage has damaged things.