Outdoor solar/ups output voltage drop

[Zozew]

Hello,

I have this outdoor ups, a chinesium product with great specs and has worked great but now it started outputting around 95v instead of the 220v like before. it also makes a weird kinda loose transformer humming. I've tried getting a datasheet or something from the manufactures but no luck...anybody has any idea what I should try and look at? or if there is some common component that is weak in these products etc...? When I switch on the inverter at the back sometimes it doesn't turn on and sometimes it does. There is a diod on the control board that lights up if the inverter is on. Relays work fine as I can hear them switching when I unplug the UPS. The passthrough mains works as well only that it outputs 93.5v now instead of 220v.

I've recorded a short video where you can hear the humming and see the diod that lights up when the inverter actually is on.

 

[Mickster]

Not sure if it's the lighting, but can you have a closer look at the cap in your pic below?
The top kinda looks like it may be starting to bulge.

 

[Zozew]

I checked all caps and they look ok...what do you think that noise is coming from...?

 

[Zozew]

Just wanted to let you guys know I found the issue, it was one of the transistors that was shorted, A quick search on aliexpress and a few weeks later and the UPS is up and running