Fixing an ESPRIMO Q910 power supply

At work we have quite a few Fujitsu Esprimo Q910/Q920/Q930 Mini-PCs. They offer quite a bit of power and easily fit on every desk. The ideal office machine ... except when they break :(

The older models have an external 19-20V power brick which seems to be identical to a notebook charger. It doesn't look very stylish but usually you can hide those things behind the desk or just drop it on the floor. There's a mess of cables anyway, so what's one more black box between tangled-up power, phone, Ethernet and USB-cables? Nothing really. The good thing about this solution is that if an external power brick breaks you can just replace it. On the more recent ones however they have decided to "fix" this problem by building it directly into the PC. And by building it into the PC I mean straight on the mainboard. ARRGH!!!1!1!!!1eleven. No replaceable parts for you, customer! Planned obsolescence, anyone?

Of course just over the last year two PCs already shat themself right after coming out of warranty. Weird coincidence, right? The main MOSFET or a resistor next to it exploded and left a nice stain on the mainboard. So, I guess we need to toss the whole mainboard, or the whole PC, like our corporate overlords want us to, right? NO! Reparing the supply by replacing the burnt components is out of the question since the whole area around is charred. Charcoal is a reasonable conductor and it would just short everything out.

Luckily for us though they didn't move too far from the older design. The mains supply is quite simple and just generates a single 20V voltage. All the further voltages you'll find in a typical PC are derived from that using DC-DC regulators. They even provide two nice big testpads to solder on directly attached on the 20V rail. 

So on those two PCs which broke I just desoldered all the components of the power supply, put in a DC-Jack and now they run on one of the older ESPRIMOs external power bricks. I don't known the internal supplys current rating but even under full CPU and disk load they work nicely with the new external supply. If you are shopping for a new one get one with at least 4A (80W) output just to be on the safe side.

TL;DR - Here's how to fix it (at your own risk):

1. Totally disassemble the PC, and yes TOTALLY disassemble it. - On the second machine I even had to briefly take off the CPU cooler. - Take it apart until you have the mainboard in your hands. Remove the black black power supply cover. This photo shows the mainboard with the power supply area highlighted:

   
    

2. Now, look at the bottom of the board. If should look similar to this:

   
   Remove the diode (black brick on the left). I removed most of the components from the top side as well but if you want to do it fast, just remove this diode. You need a big soldering iron. Use lots of solder and lots of heat to just heat up the whole plastic package. Or, if you have an SMD rework station, use that.
    

3. Finally, wire in a new DC jack and run some wires over to the 20V testpads seen on the first picture. The jack sort-of fits into the hole left by the AC-jack. Be careful about the polarity, though.

   

4. Finally, reassemble everything and power it up using a new 20V notebook charger or older Esprimo power supply. Enjoy getting many more years of life out of the hardware!