if you see heavy dust, probably that be the cause.
replacement wise, depends on where you are located,may be cheaper to just buy a replacement PCB. or other units. PCB version or model needs to match as there are several versions of S7 exist
I can't move the S7 to another room but I can power down the S5 for a trial period. So I will do that first. As for the fans I just checked and they are running at 4500 rpm or so.
I have seen a lot of dust on the fans so I imagine there's dust on the inside. I saw a few videos on how to clean the S7 so I will take that up once the S5 power down test is complete.
As for repairs it's too costly for me to send it for repairs. Are all boards on an s7 the same? this way I could just get a new-er board and keep as spare.