HP T620 Thin Client - PSU Hack And Windows PC Modification

[Mads Barnkob]

The HP T-620 Thin Client is a powerful little machine, that with ease can be hacked into using a random 19VDC PSU and run Windows as any normal PC, easy and cheap PC!

This thin client was thrown out, without anything else than the box itself, no power supplies, no nothing.

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The port and connector layout from the manual shows that the HP T-620 models needs a 19VDC power supply. A little searching showed that it was not as simple as just supplying it with 19VDC. HP has put in a few tricks to make a "smart laptop charger" so that you can only use their chargers.



The "smart laptop charger" restriction can be bypassed with a simple current limiting hack as per this little schematics.



All credits for this hack goes to:  http://nerdipedia.com/wiki/tiki-index.php?page=Smart+laptop+charger

The machine itself is powerful enough to put a little work into modding it into a PC, running Linux or Windows off a USB disk or for some models, you can even find a spare SSD slot on the motherboard, unlucky for me, this model does not have that option.

[Experimentonomen]

I always through that smart psu thing was like eeprom based where the middle pin is an all digital thing.

[Hydron]

I always through that smart psu thing was like eeprom based where the middle pin is an all digital thing.

For Dell laptop chargers this is indeed the case - they actually use the exact same plug as the HP ones, but with a maxim one-wire bus EEPROM chip wired to the central pin. This chip or the wire going to it is easy to kill (there isn't any added protection on it, and it's 3.3 or 5V max) so it's a leading cause of otherwise good PSUs stopping working.

[latethannever]

Hi Mads,
I am trying to modify my T620 plus to use a regular HP notebook power adapter (hp p/n 750413-002) which has the correct size connector.   However, when I plug in this power adapter to the T620+ and try to boot by pressing the power button, my power button turns red and beeps 4 times (unauthorized power adapter)

In you video, I can't see which pins on the power connector you solder the 330k resistor to.   The middle pin is the "signal" pin, I verified this by checking the resistance of the middle pin and the "middle hole" in the power connector.   However the two outer pins seem to be connected together (I measured 0.2 ohms between the two outer pins).   

does this mean that I can solder the 330k resistor between the middle pin and either of the outer pins on the 3-pin power connector?

Thanks

[Mads Barnkob]

Negative connects to the outer connector, positive to the inner connector (both are bridged as you also noticed) and resistor connects from positive to middle.

I hope this picture can help you

[latethannever]

Thanks, your diagram makes sense.  I will give it a try this weekend.

[latethannever]

Negative connects to the outer connector, positive to the inner connector (both are bridged as you also noticed) and resistor connects from positive to middle.

I hope this picture can help you

Hi, I tried this and it worked nicely on my T620 plus with the HP notebook power adapter (hp p/n 750413-002).   I used a 300K resistor between the indicated pins.  I cut short the resistor leads and covered the resistor with a piece of heat-shrink to keep it tidy and prevent any accidental shorts.  The power button turned white when I pressed it and the T620 booted up correctly.   I'ved updated the BIOS and now I will use it to build a PFSense Router.

Thanks again for your help