Samsung N150 Netbook Repairs.

I have one of these netbooks that ran linux very nicely (good wifi,runs cool and quietly) for quite a while, but then suddenly stopped charging. The netbook has very good battery life, and makes a very good travel companion. It was very much worth repairing it.

The first thing was to haul the back off after removing the battery (nicely described on you tube). All the screws need to be removed from the back (13 total) . The back then clips off easily. Two of these screws (marked "KBD") also hold the keyboard down on the front side of the PC. The key board lifts off easily after unclipping a flexible ribbon connector.

The main board is held down by two easily visible screws. The cables connecting to the main board are a four pin plug , a small flat ribbon to the glidepad, a SATA disk cable, two gold coax antenna cables, and a display connector. Only the first four need to be unplugged to lift the main board up.

In the case of my PC there was obvious damage to the underside of the main board near the power input jack; there was a burnt and destroyed component.

A repair seemed very risky without some schematic information. A hunt on the net led to all sorts of noxious sites that were of less than no value. Fortunately there was one outstanding exception, namely http://elektrotanya.com/ . This latter site dedicates itself to reducing E-waste, and without it my netbook would have definitely become E-waste! Many thanks to the site's maintainers. I was able to download service information (specifically full schematics), more than sufficient to fix the PC.

The fault in the netbook was a fused input capacitor next to the power jack. It had burned and damaged the surrounding area. The burnt PCB material was smeared across a neighbouring 100k ohm resistor which was part of a soft turn on circuit. The debris reduced the value of the resistor < 10k ohm, preventing the pFET switch from turning on. Cleaning the charcoal from the board returned the PC to proper operation.

It looks as if the voltage margin for the two input supply capacitors is narrow. The input voltage is 19 volt, and the capacitor rating seems to be 20 volt. It is easy to imagine that the inrush and overshoot on plugging in the jack could take the capacitors momentarily beyond their safe region, and that other PC's in the same model range have experienced the same fault. It looked as if the component had failed quite some time before the fault became apparent. This fault is self aggravating, since the pFET transistor overheats if not turned hard on, and contributes to the surrounding damage and contribute to the capacitor failing.

The fault is probably brought on as a result of the heat from the pass transistor. For this reason it is probably a good idea not to use the PC while charging with a completely flat battery. Better to recharge the battery before turning the PC on.

The netbook is well laid out, and is open and easy to work on. The SMD components are small.A few needles and a USB microscope were very helpful.  It is worth noting that the on/off switch will not work if the PC is closed. I did not notice this, and took the mother board back out until I realised!