Fixing an Airport Basestation
 
Resurrecting an old Airport Express (APX)

Introduction

My home network consists of a broadband modem and two Airport Express (APX) boxes, both mounted in Belkin Airbase stands to improve cooling, as the Airport Express produces a significant amount of heat.

airportexpress


The first box was used to provide the main network access point, and the second was a wi-fi bridge and print server. Recently, my one of my c.2005 Airport Express Wi-Fi box died and I was left with three options.

  1. Run my home network with one Airport device, and connect all printers to static computers.
  2. Buy a replacement Airport device
  3. Try to repair the system.

Research and Methods


I decided to instigate option 1, whilst investigating option three. A little searching with Google located a few useful sites detailing the procedure.

http://archive.macfixitforums.com/ubbthreads.php/topics/351479

http://echoone.com/airport-express/

It transpired that the Airport Express comprises of two discrete parts, the AC transformer (111/240V) and a low voltage APX component required a 5V d.c. feed and a 3.5V d.c. feed. These sites suggested that the mains transformer had burnt out, and that the wi-fi, Ethernet, Air-tunes server and print-server systems were probably still working.

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I took a Dremel to the APX case – which effectively destroyed it and discarded the AC Transformer, but I was able to salvage the important part, the APX electronics.


Following guides on the web sites, I bought the following components from Maplin Electronics (www.maplin.co.uk)


  • N57CA TS1086CZ-3.3                       N57CA £2.78
  • RA49D Monores Cap 0.1uF     RA33L £0.58
  • KQ70M GenElect 100uF 25V              AT02C £1.08
  • USB Dual Power Supply     N15GN £16.99

Also, a small quantity of strip board and wire was obtained, and an old USB lead was scavenged from a box of spares.

The following wiring diagram was used and the circuit was constructed, with all wires soldered to the stripboard.
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The Red and Black leads from the USB leads were used to provide a 5V input supply, and this was soldered directly to the stripboard. Since two output voltages were required, a 5V supply was fed via smaller 0.1uF capacitor directly to the red 5V input line on the APX, the voltage regulator in conjunction with the 100uF capacitor was used to provide a 3.5V supply to the two orange input lines and all ground lines were connected.

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A new case was constructed using a 3D Rapid Prototyping System (Dimension 1200ES). This was designed using SolidEdge running on Windows 7 (via Parallels Desktop) and both the APX board and the new Power supply board were inserted into the case. Access holes were designed to allow Ethernet, Audio and USB output from the APX: additionally,  a window for the APX status LED was also included. A cable flange was also used to secure the USB power lead to the case.

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Finally, the Lid was attached and the USB power supply was connected and Airport Utility was configured to integrate the repaired APX back into my home network.


Conclusions


What started with a dead APX system suffering from a burnt-out AC transformer, concluded with a fully functional APX system running from a UBS power supply.

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With hindsight, a few modifications could be made :-

Instead of wiring the USB lead to the PSU board, a USB socket should be used, either case mounted or board mounted.
The voltage converter generates a reasonable amount of heat, to prolong the life of the repaired system a suitable heatsink can be bought from Maplin  (JX21X - £0.85)