I have a blow 650VAS UPS and need a circuit diagram / schematic, appreciate if anyone can help

 

You won't get one, you'll have to reverse it yourself, what is the 8pin chip number and start with that.

 

This circuit looks exactly the same as a mecer 650va circuit. I'm also looking it's circuit. I suspect one is a clone of the other.

 

I have a blow 650VAS UPS and need a circuit diagram / schematic, appreciate if anyone can help

It's not always easy to fix these things. You can just check the power transistors as they usually blow, and the electrolytic capacitors as they age badly. There could be other parts too though that work with the transistors, such as whatever drives the gates or bases of the transistors.