Yamaha PSR-A670 (music keyboard) not starting

Hello

I am P Samuel, from India. 
My contact details: email id: psamuelmerchant at gmail point com
I have one Yamaha Keyboard. It is not working from 4 months. I do the electronic repair but here I am not able to find the fault and I am stucked on the way. 
It was working and one day I on it but never got it on, I tried it again and again but no use.
I check the power circuit and I found transistor faulty and I replaced it but even though not starting. 
Pls help me. 

Regards.