Thanks to Jen, we identified a Fairchild Power Switch that was identified as faulty in her dead APX, and later on in numerous other defective APX. Replacing a defective DM0265 by a new one was not really successful, and could restore APX functions only in few cases. So we went on to identify a faulty component located upstream of the power switch, aiming to demonstrate that only the power board was dead, while the wifi board was still perfectly functional. Thanks to data we have collected over months, Henrik, a member of hardmac forum has successfully resurrected its dead APX. He has published the procedure on his website (be careful it is relatively tricky).
Once disassembled, we were quite amazed by the poor quality of both design and manufacturing of the power board, especially when comparing it to the clean wifi board.
Once externally powered, the resurrected APX recovered all its features (airtunes, USB printer and wifi) exactly as one would expect it:
We then looked further at the power board, and identified 3 capacitors (thanks to the reference schema of the Fairchild DM0265). When measuring their specifications, one of then was displaying 0.1 µF instead of the 10 µF specified. It is well known that capacitor lifetime decreases rapidly when exposed to high working temperature. We identified the capacitor manufacturer as Capxon. The TechNote reports that the capacitor will retain 80% of its nominal specification for 2000 hours (only) at 105°C. The APX is a closed environment and its enclosure can get really hot as many users have already experienced it; it can even be so hot than it is not possible to hold it in hands (external temperature is much lower than the internal one, or the one measured on components). In an additional info sheet, Capxon indicates that the maximal working time of this capacitor will be around 16,000 hours when run at 75°C... in other words, around 20 months. Even though it remains an estimation, the temperature factor seems to be critical, and could explain why so many dead APX have been reported in Australia.
So, life of an APX is as follow: once plugged, the capacitor loses its specifications rapidly due to the closed and warmed APX enclosure, then it fails, leading immediately to the death of the Fairchild DM0256 power switch; last but not least, the fuse blows as one would expect it for a safety component. You are then left with a burned power board, and the APX is reported dead.
We will continue our investigations in order to demonstrate (if it is still necessary) that the short lifetime syndrome affecting AirPort Express base is directly linked to the use of inappropriate/poor quality capacitors on its power board. It is about time for Apple to react, in some countries such information will be enough to launch an action claiming a faulty design or a hidden defect. Not sure that Apple would like to hear such negative advertising campaign about one of their product. In addition, some users might even claim that Apple did it on purpose to ensure that users will buy a second APX when the first one fails.
The APX remains a interesting product but its poor reliability deserves it. Apple needs to communicate if this rather poor quality manufacturing of the power board is directly due to its original design, or is it Foxconn that decided to reduce quality to increase margins without referring to Cupertino?
