iPod charges but will not turn on and not connect to itunes

Hi,

after replacing ipod screen i cannot get ipod to turn on or connect to itunes. I have read another post from last January that described a fix involving shorting the positive battery terminal but that has not worked thus far.

In comparison to a working ipod i have picked up some differences with a mutlimeter on the four tab solder point for the sleep on/off/volume cable.

Where a working ipod will show roughly 1.8v on the first, second and fourth tabs (from top to bottom ) when turned on.....and only on the top one when the sleep button is pushed.......my broken one shows 1.8v across those terminals always. Except when i push the sleep button. momentarily the voltage drops to nothing on the first tab then jumps back to 1.8v.

Can anyone tell me does this point to a motherboard failure/shorted component? Or is there possibly another explanation .....the cable seems fine , the battery charges, drops to zero when shorted and then charges up again when placed on charge ....but i dont get beeps or a screen back after this?