Need Help !!USB damaged due to reverse polarity!!
 

I have seen and read threads related to usb not working due to broken usb ports, but I have a bit different situation. I was making a home made usb charger... but seems that I had reversed the polarity and damaged/destroyed my USB port's connection with outer world.

Dr_frost_dk suggested me to connect the fuse terminals as fuse may have been wasted. I broke the fuse and connected the two terminals with solder itself... Still the usb doesnt seem to work.

Does anyone know what the problem maybe? or what else could have been damaged due to that reverse polarity. Also any alternatives to data transfer as well as chargin.

I would be happy if at least I could charge using the same port. For data transfer I can use scp, bluetooth etc etc.

I amfollowing this thread:
http://talk.maemo.org/showthread.php?t=71414

Re: Need Help !!USB damaged due to reverse polarity!!
 

Search for thread about using pins beneath battery as USB, You should find documented pictures in "broken USB idea - creating alternative connection" or something like that.

You'll find which pins are data +, - 5v + and ground. Those pins are connected directly to chip, so they come around all (protection) circuity between main USB port and chip controlling it.

Caution! As I said, it's connected *directly* to the chip. It's not suitable for day-to-day use, cause it doesn't contain any protection, also from static. You should only check if Your device is recognized via USB this way - if yes, you know that damage is "somewhere" between USB port and chip.

If USB connection can't be established via pins beneath battery, you got (for 99%) irreversible damage and it's miracle that your N900 works at all. But, i doubt that it's the case - if chip would be damaged, you would end with completely dead N900, so IMO it's some part in protection circuit for sure.

---

the most ironical part is that You've did it, cause You didn't want to "mess" with creating dual-scud - so you've used external batteries, to transfer energy to N900 via USB (and accidentally switched polarization). For me, modifying batteries (to create dual-scud) isn't hardware modification of N900 itself - but now, You've to tinker with N900 hardware *really*.

Of course I don't write it to just "make You sad". I mean, that establishing connection via pins beneath battery is "tinkering" comparable to creating dual-scud, and I'm not sure if You feel comfortable with handling it. In fact, it's easy process, but must be done right - you don't want to kill your N900 by some static or whatsnot.

I Think You may be best giving it for repair to professional repair center (by professional, I really mean it - you don't want some "joey the repairer" to do more damage to Your N900), alongside detailed problem description.

---

BTW, how You we're able to replace "fuse"? It's *really* small element, even dr_frost_dk was having troubles replacing it with wire. Also, you need to put part of screen case to get to it.

You're sure that You've destroyed and replaced *correct* element?

Re: Need Help !!USB damaged due to reverse polarity!!
 

wait.. I mentioned I connected the fuse terminals with solder itself.. I mean just with solder no wires or anything.. just connected the two terminals.

And regarding professional repair centre...I wont be able to find any in my place.

Re: Need Help !!USB damaged due to reverse polarity!!
 

So, if that is the problem then can it be repaired??
--
Also, I have ordered this n900 pcb. there is no details given but says without spares.. so I dont know if it will be usable or not.

http://www.ownta.com/compatible-noki...eparts-en.html

Re: Need Help !!USB damaged due to reverse polarity!!
 

Looks like it is not complete maybe? i do not get the bit about "WITHOUT SPAREPARTS" but if this board is a replacement for the motherboard of the NOKIA N900 then hell it is worth it's weight in gold for some on here !.

Is it possible you can post a follow up to that board and let me know it is a complete replacement or not?.

Re: Need Help !!USB damaged due to reverse polarity!!
 

Does it still turn on and work all apart from the usb functions or not ?.

Re: Need Help !!USB damaged due to reverse polarity!!
 

yes it works all good.. except for usb.

and regarding the ordered pcb... it will take at least 15 days and at most 1 months to arrive. will update if it arrives before i decide and will be able to sell this set.

Re: Need Help !!USB damaged due to reverse polarity!!
 

I do not like that mod at all and i knew it would give problems the moment i seen it but without looking at your device i would think that the usb transceiver chip has gone but i could be wrong, you could take it apart and look at it and associated components, too many to point at sorry to say, and if any have fried anything you will see straight away i am sure.

Double check all your wiring in case you have made any shorts with the pads etc and if you get it apart try to link wire the port back in place, not easy i know but hell it is worth a try, i only wish i had it here to look at.

After looking at the pic which is not good, i can see components missing and the board itself is not the same shape as the one actually inside of the N900 but hell it aint a lot of money so see what you end up with.

Sorry i can not help you further unless you go inside and check everything.

Re: Need Help !!USB damaged due to reverse polarity!!
 

Its normal chinese marketing... they dont know english so well, and have seen a phrase somewhere else that they think looks cool to have on their page too.

Re: Need Help !!USB damaged due to reverse polarity!!
 

Yes but look at the pic of that board and if you have a pic of a N900 board then compare it and you will see what i mean... what do you think?.