If you are in Bangalore and near Marathahalli area, you can pick the phone to LG service center which is in the alley next to golkunda chimney hotel. It looks like many are using the service from this center. Just 15 min, you can replace the power button on the mother board .
Mr Manohar is well knowledgeable in this issue and he does it with ease . You can actually see what is he doing from the service window. No bull $@$* talk on replacing the motherboard unlike other service center.
I was able to do it in Just 15 min for Rs370 with invoice copy from LG center.
P.S: If you try their number shown online, you will be disappointed that no one is picking your call. All you have to do is visit their shop by opening time 10 AM and you can finish your task in 15 - 30 min depending on the Queue there. Not much Queue when i went there. I was able to come out in 15 min time finishing the payment. the shop opens from 10 AM till 6 PM. Mon till Sat.