Rants, Raves, Reviews

Postmortem of the Telecom USB modem

By Gary R, in , posted: 11-Jul-2007 17:36

Yesterday I blogged about the lovely new Sierra Wireless 595U EVDO USB modem that I had won in a prize. The first review was about the actual USB device which has survived in its intended form for 24 hours. This morning I set about pulling it apart to extract the radio module. So, RIP USB and here is part 2.

Firstly, when the front cover and battery are removed there is a noticeable white sticker which is covering a dummy SIM card socket.


With the front cover removed the solder lugs for the vacant SIM socket are visible near the top of the front of the board. Very smart design as Sierra obviously use the same board and case for the AC875U HSDPA USB Modem.

Next, we removed the back cover which revealed the main antenna stuck to the top of the radio module which is plugged into the Aux antenna port, the external antenna socket is plugged into the Main antenna port. The two antenna ports are for antenna diversity but it appears that this feature is not used.


The antenna is stuck to the radio module by way of sticky tape backed foam. We just ripped it off without worrying about it too much. This leaves all the bits separated. The main board, the module and the antenna.


The module is the bit we actually want:

The USB Modem uses an MC5725 mini PCI Express module. This module uses the Qualcomm MSM6800 chipset. It supports both 800MHz and 1900MHz CDMA EVDO. The module has 3 end points which are multiplexed over a single USB (Mux) interface. This means that the control, debug and data channels are all accessible simultaneously over USB.

Now that the module is removed we have placed it into a router daughter board:


The daughter board fits into a Ctek 4200E SkyRouter.


Now, finally we can try out this industrial router that we imported 3 months ago. We are the NZ distributor for Ctek but up until now we have not been able to get our hands on the MC5725 module. This is the same module that is used in some Toshiba and HP laptops as an embedded 3G modem. The next step is to test the router and then submit it to Telecom for approval. Hopefully, we will soon have a source for the modules and we will no longer need to butcher USB modems.

As a sideline we pulled apart the desk cradle and our suspicions were confirmed. It does not contain any electronic components. It is simply a USB socket, cable and metal weight.


Other related posts:
Acer Aspire One Netbook Teardown
Vodafone NZ Launches 3G Acer Aspire Netbook
Sprint USB multi 'G' modem

Comment by paradoxsm, on 12-Jul-2007 22:56

i love this, maybe i should post some teardowns of phones, todays ripper task for me was ripping apart an apt nokiacable and an original kyocera databable and fixing my poor ipod earphones.

I'm going to turn the apt one into a multiport for nokia pop port testing and try and use the Kyocera cable as a generic test.

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