View Single Post
Posts: 21 | Thanked: 6 times | Joined on Jan 2010
#116
Originally Posted by jabawok View Post
I managed to repair my faulty USB port today. Many thanks to everyone to posted pictures to this thread, it was of immense help.

I apologize for lack of photos; I found myself reaching for my N900 several times to take some shots, then realised it was in bits in front of me :P

My port was still attached, but had dry solder joins on one or more of the 5 pins connecting to the pcb. (this means the solder has snapped and the legs are not bonded to the board, they are just touching it [occasionally, in my case].)

This symptoms of this are:
- Phone charges but only if you turn it upside down
- Phone charges but only if you fiddle with the usb cable till it's "just right"
-Phone charges when you hold the usb connector in the socket (and possibly gently push)

I found it got progressively worse to the point that I would spend 5 minutes every night making small adjustments to the cord and phone until it would start charging.

I pulled the device apart according to Nokia_N900_RX-51_Service_Manual_Service_Level_1_2.pdf (google for it).

I stuck a small piece of paper over the camera lense to prevent dust getting in, and removed the RF shield from the chip immediately next to the usb connector. The little clips on the side just click off with a small flat blade screwdriver. I then got some small side cutters and cut a very small section out of the RF shield rail (what the RF shield clicks down on) to gain access to the back of the USB connector. This should expose the surface mount solder points.

I then wound a pin around the end of my soldering iron, tinned it on and chopped the end off the pin off (it was too fine). From there I managed to heat up each contact till the solder re-flowed (I didnt apply new solder at all). Its very difficult to see exactly what you are doing with bare eyes - you cant tell if the solder has remelted. I experimenting with various lengths of time holding the tip onto the joins. Between each attempt I connected the screen and held a battery on the back of the board, to fire the device up and test for any improvement to the usb connector. I found that the best approach is applying the tip from a 45 degree angle, to clear the RF shield bracket and have a degree of visibility to the pins.

Once I had it reliably charging, I scraped away 1mm of green enamel on either side of the connector where the sides are soldered down, and applied a nice amount of solder to each side to lock it into position forever. Its imporant to not heat the connector up too much else the internal plastic parts will melt, but enough so that the solder "flows" onto the connector and onto he board where the enamel has been scraped off. Also take note of where the board fits into the plastic shell, there is a screw right next to one side of it; too much solder on the board will mean the board wont sit correctly on that mountpoint.

Hope this helps someone.. attached are some shots of my makeshift SMD soldering iron mod.
This seems like what I need to do to my wife's N900. For over a year she's been using an external battery charger and she's constantly changing batteries. Of course she didn't bother to tell me that the USB cable wasn't charging while it was still in warranty. Anyway I want to get her N900s USB port working properly. I disassembled it yesterday and this is what it looks like:

Is this what yours was like? It seems like the method you described would apply to my problem. Reading your post made me hopeful that I might be able to fix this without too much trouble.
I read about using Kapton Tape on adjacent components to reduce the risk of damage due to inadvertent heat transfer. Also I thought I might just get a sacrificial soldering tip and sand/grind it to a fine tip to do what you did. It seems like there may be enough solder already there to just re-flow each contact if I keep a steady hand. I'm guessing the less I mess with it the better.
And It'd probably be a good idea to also reinforce the solder at the mounts, as you did, while I'm in there. I read a whole thread that strongly advises to reinforce the USB mount as a precaution to a known weakness of the N900.

I had to put hers back together as is, now I'm trying to research the best way to fix it and what stuff I need to get to do it.

Last edited by TheJason; 2012-05-01 at 02:19.
 

The Following User Says Thank You to TheJason For This Useful Post: