Binatone s500 won't turn on

Hi ! I have a binatone s500 , i have bought it form ebay as spares or repairs with a faulty screen , first i have checked the screen on another binatone and is fine . The problem is that it won't turn on. Red led charging light is on but no matter what i do , tried reset it a lot but nothing. Today after two months since my last attempt i connect it to the pc with a usb cable and it started and working perfect. I turned it off after 20 minutes to recharge the battery faster but now the same problem like before. Red led and won't turn on no mather what and is it also not recognized by the pc anymore.

I've seen a F430 with the same fault.

It seemed to refuse to turn on if it was in suspend, but was ok if it was turned off completely.

Either pressing and holding the reset button while on charge, or opening it up and disconnecting the battery allowed it to be woken up.

I didn't get any further with fault finding as the owner decided it wasn't worth the hassle and threw it away and bought another.