Reparing a HP-Compaq nx8220
Fan failure

   French version  

Updated : 11 feb 2009

Warning ! Read carefuly !

The manipulation presented below is for information only, and is not recommended by HP's support. It requires disassembly of the computer and editing sequipment (cutting and soldering wires).

Accordingly, the realization of this manipulation will make your warranty void, and may damage your computer. If your hardware is still guaranteed you should first contact HP's support.

If your desire is to replace a defective part with an original part, you can contact Europarts in Europe.

The achievement of this manipulation is done at your own risk.

Origins and symptoms of the failure

Failure of the motherboard, that doesn't power the fan correctly. The fan no longer turns, even when setting "Fan always on" in BIOS. Temperature raises up to 90°C (194°F), with a risk of damage !

Fan : nx8220 fan specs are 5V and 0.18A (180mA). Some models use a 5V / 0.21A fan.

Solution I've found

Power the fan thanks to USB power (5V 500mA max), inserting a variable resistance to reduce rotation speed (less noise ...)

Electrical diagram :
Electrical diagram

The choice of a 50ohm resistance comes from the fan specs. It allows a minimum voltage of 2.5V and a 50mA current, for a slow rotation speed, to keep a minimum air flow.

I had no 47ohm variable resistance (closest standard value) so I used a 100ohm // variable 100ohm. You get similar values (see table).


1 ) Unplug the computer, remove the battery, press the power button for about 10s (not to have any residual power).

2 ) Remove the keyboard : remove the two screws that secure the keyboard to the computer (at the back), then slide the four keyboard retention tabs toward you (located between ESC and F1 keys, F4 and F5 keys, F8 and F9 keys, F12 and DELETE keys)

Remove the two screws

Slide the 4 retention tabs

What's inside :

Inside the computer

3 ) Disconnect the fan cable from the system board :

The fan and its connector

Be careful : fan wires
- black wire : power (+5V)
- grey wire : ground (0V)
- brown wire : informs system board about fan speed, do not touch it !

You must respect connections, otherwise the fan will fry ! (it happened to me, just by touching the brown wire with the +5V...

Fan connections

4 ) Preparing USB power

For this, the best thing to do is to get an existing USB cable, I took one from an old USB hub...
More informations about USB connectors : So use the red wire (+5V) and the black wire (GND). Do not use the shield wire (useless here).

You can prepare a small assembly, it's practical. The best would be to solder all wires and resistances, do this after having tested everything is OK.

Principle :
Connecting the fan to USB power
Red dotted line : my assembly
Black dots : connection points

The final assembly

2 black and red plugs are still here, I used them to check voltages.

Résults, conclusion

Even if I sacrified a USB port, 1 year later, the computer is still working !!!

Tips :
- Use SpeedFan, to know precisely system temperature. If temperature is too high, increase fan speed !
- Be careful to always have USB power !
- Do not forget to plug the fan ! It might be a stupid tip, but you'll be warned... (so use SpeedFan !)

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