Blank Screen after logic board and battery change

Hi everybody,

I am stuck with the reparation of my iPod Classic 3rd generation (model A1040).

I had to change the logic board because a failure and, at the same time, install a new battery for better battery lifetime. I bought both things in eBay. My problem now is that I have a blank screen after the apple logo.

I can restart the iPod pressing Menu button + Play/pause button: the iPod restarts, the Apple logo appears, and then… blank screen.

I can activate the Disk Mode pressing Previous and Following buttons after an iPod restart. The screen shows that the Disk Mode is activated and I can plug the iPod to my Macbook. iTunes recognizes that an iPod with problems is connected and I have 2 options:

• update the firmware version to a newer one.
• Restore it.

I can not restore it because iTunes says that I need a FireWire connection that my laptop does not have. However if I try the same operation in windows (with iTunes for Windows) there is no problem and after restore it (or update the firmware version), a message appears for disconnect the iPod of the laptop, connect it to an external power supply and finish the operation.

Then, I restart the iPod to exit the disk Mode (pressing Menu button + Play/pause button), the ipod restarts, the apple logo appears, a progress bar appears and is completed and… blank screen again.

I have repeated the process many times and alwaus have the same result. Something strange is that always iTunes says that a new firmware version is available, so I can understand that the previous attempts to update do not work properly.

I would be very very grateful if somebody could help me with it.

I hope to not lose my loved iPod. =)

Regards