Thanks for your help Hansson. I'll remove the caps for the time being. Should they be replaced with exactly the same type of film cap or other material cap can be used ? Replacement options are limited in India.
They don't have to be exactly the same but they need to be class Y safety rated because they go from live and neutral to ground (chassis) so a short there would make the chassis live at mains voltage (Y class caps are guaranteed to fail open, not shorted).
P.S: You should replace all "Rifa" brand capacitors in the unit if one has failed the others are soon to follow...
Not much damage under the high voltage cover. But there is a lot of corrosion around U555. The traces have become discolored. I pretty sure someone has done resoldering with low quality flux paste, hence the burnt flux everywhere. I'll resolder all the corroded points.
I don't really agree, look at the first photo you attached around the screw hole in the PCB: there is corrosion underneath the soldermask.
That is something that usually only happens when a battery leaks, but there is no battery in the unit which is why I said something must have contaminated it.
Otherwise I don't know how this could happen...
Anyway trouble-shooting is straightforward if it is complete dead: just download the service manual and follow the mains input.
The failure could for example be C904 having failed shorted (it is another Rifa cap).