inverter showing wrong voltage output
I recently got a used 24v 3000watt 120vac 60hz reliable pure sinewave inverter. It has a 2 display on the front that shows the dc voltage input and the output voltage reading. In normal operation it always shows about 120 -122vac output on the display.
Recently i was pulling about 1100watt from it constantly and I realize that the case was getting very warm to a point that i assume the fans should have chip in by now which they did not so I assume maybe it wasn't time yet/not hot enough or probably the fans or not working. After a while I heard a poof sound and the inverter was still on but no output. I turn it off same time. I waited a while and turn it on again and it was working normally but this time the output voltage now drop from 122vac to 110vac.
What could have gone bad in terms of when I heard the poof sound? what could have cause this to happen is it because it got too hot and the fans did not chip in to cool it down. What would cause the voltage to drop so low.
I have not open it as yet to check I am just waiting to hear someone's input on the matter first so I can now what to do when i open it to repair it. It is still working now but just with a much lower voltage output and I really want to get it back to the 120- 122vac reading please.
So please help me out in this regards.
I anxiously await your responses.