replaced battery and momentarily turned on then died
I replaced the battery with one I bought from you guys - it worked then died and now won't do anything- it may be possible that my charging cable is worn out but wonder if there is some other troubleshhot I could try - I think I was using a cheaper version of the charger usb cable or one for my iphone but not sure if that was the problem. It is the original upod usb cable that I think is too frayed and that might be it?
To rule out the charger cable, see if you can borrow one that's known to work from a friend (or check if yours is working on a friends iPod). If it still won't charge try to reconnect the battery (did you use the locking mechanism on the connector correctly?).
If that doesn't help, then three things come to mind as possible causes: the battery, the ribbon cable or the connector/logic
It seems unlikely that the battery is the problem, but it can be examined using some kind of meter, that I don't know about. If the ribbon cable has been damaged, it's most likely to be where it's bend. But my guess is that if reconnecting the battery doesn't help, then something has caused malfunction either in the connector the logic board. As you changed the battery you could have touched a component or something else might have happened, that would cause corrosion leading to malfunction after some use.
It might be something that can be fixed by a cleaning. Or has something happened to your iPod, like a liquid spill?
good luck and please update on progress