Not even getting if it is charging or not

My phone is switched off at this moment , when I plug in charger it's showing red LED as the mark of charging but when I try to switch on its just displaying Sony logo and vanishing, and after removing from battery even charging for 2-3 hours when I tried to switch it on showed 3 blinking indications of red LED as the mark or battery dead. It's motherboard issue I guess where I can buy new motherboard online as Sony service centre wil charge an appreciable amount for this..

I forgot to mention I have got my charging port changed and still it is showing the same issue.