How can I make a CyberPower 1500va function only as an inverter?

[Skyline3499]

Hi, so I have a CyberPower 1500va that I would like to function as an inverter as soon as power is hooked up to it. The little circuit board coming off the big board with all the inverter parts nad battery charging parts is broken. It used to turn on when you hold the power button for a couple seconds even if only a battery was hooked up. I'd assume there's some pins that need some sort of signal going from that big board to the little one. I don't have an oscilloscope, but I have a couple bench power supplies and a multimeter.

 

[riccardo]

It pretty hard to help without some diagrams or at least pictures to go on. Could you post them please so we can have a look

 

[Skyline3499]

It pretty hard to help without some diagrams or at least pictures to go on. Could you post them please so we can have a look