hardware problem trival to repair if you know what you are doing .
For me i would start with some flux on the usb port and heat it with a hot air gun ment to repair such stuff it usually goes like that sometimes a replacement is needed too .

or else you will need a multimeter to find out whats wrong
first thing to do is check the battrey terminals and i think you wont even need to open the phone to check whats wrong but reparing n900s is terrible job .
for now i only have one and it feels bad that my usb acts up too

though my port was solid it is hostmode that destroyed i was like crazy plugging all kinds of usb stuff i could find and i am amazed what the n900 can handle and the most intresting pratical thing done was a usb lamp plugged directly onto the n900 providing light hundred times better than the flashlight and yes its awsome doing macro video with it.

i ll probably open up mine pretty soon
also i got a spare board with a ripped usb that vivrates and lights up as the battrey is put in i ll see if i can find out why.

can anybody tell me a usecase for the board or rather how to use bluetooth or wifi or cellular
available parts
mainboard
display module
battries

current condition---
ripped bad condition port
starts up as a battrey is plugged in
stays at nokia logo

i can probably repair it but what it would be good for ?