I have been using my N900 for about six years with little problem. Recently I went camping in Giant City State Park in Illinois. Now I have a problem. It started when I was trying to charge the N900 in the lodge there. The N900 shut down. The battery drained, and I haven't been able to charge it with the normal power cord. I hadn't been able to get it to charge for weeks. I've been using an external battery charger. The USB connection hasn't fallen off, I can still stick the plug in. Too, I have an LG phone with a similar microusb charger. I stuck that one in last week, and it works to charge the N900. Unfortunately I can't get the N900 to connect to an external cpu for "mass storage" file transfers. I also noticed that while the N900's off it drains the battery; the keyboard stays lit. So what's wrong?

your USB *is* very likely broken. sometimes, even though the port seems intact, the pads might already be loose. also, the protruding part inside the port can break on the inside.

Yet a similar charger works.

I have noticed in the past that ..compared to the n8x0's chargers..
the usb chargers for the n900 can be more finicky ..
I have had some n900 chargers that worked fine forever and a day...
others that worked fine or seemed to ....and then after a few years started becoming problematic...
In the last 5 years I have found 2 n900 chargers (official nokia ones...at that...) that I labeled problematic and set aside..

If the battery is fine...
and the internal connection is fine..
and it works fine with another charger...
Then I suspect the charger is the culprit...or a leading cause at the least...
(based on what odd behaviour I have come to see.)

simple test - does the N900 charger work on another phone? :-)

That is a clear indication that your USB port is broken. The fact that another charger works may be because of a very slightly different shape of the connector, possibly the teeth, pushing the connector less off the PCB. That is also a good hint that the problem is fixable, you just need to open the phone and solder the connector back down.

I don't get that bit.

Get the app healthcheck from the repos and see if your KB sensor is working.

In one case I had a N900 keyboard light logic stuck to ON, I eventually just desoldered it, the battery connection was wonky and I constantly had bad shutdowns which eventually lead to the stuck LED, it could have been one of my fake 'new' Chinese (new exterior) N900 refurbs. It persisted through several full reflashes and being left for several months without a battery.


I have done the microUSB fix before, if you can do SM soldering it is not so bad, see this thread
http://talk.maemo.org/showthread.php?t=37107
and there is another with more soldering tips, and less advice to get a warranty replacement.
http://talk.maemo.org/showthread.php?t=75920
Hot air and solder paste fix is ideal but I have always just used a soldering iron and regular 50/50 lead/tin rosin core solder. Be sure to solder wick away as much solder and IMHO increase the solder footprint by scraping more ground plane clean and tinning it a little. Just please be careful removing the port if you are replacing and not just re-soldering the broken connection as it is super easy to rip up the pads.

I have done never soldered a thing in my life, but I did lay soldering lead/tin in a channel in a wood table I built once, I just never melted it.
Maybe I'll try soldering this, but will have to practice.
Any chance I could tap it into place? I'm going to replace the N900 screen soon, so I'll have it in parts.

Take some broken surface mount electronics and try to solder and unsolder parts from the printed circuit board. Or maybe there is a phone repair shop where they can do a hot air rework fix, which is actually preferred for surface mount components.

Yep, the shift, function and ctrl keys stay brightly lit while the things off. The Q, A, Z are lit but more dimly; as are each keys progressing to the right.

What are the risks to the device if I try soldering in that area and screw it up? What can get damaged around there?