Repair Levoit air purifier PCB due to wrong 240V AC power plugged in.

[hanschee]

Greetings! Found this forum searching for help to repair a Levoit air purifier and hope to get some tips.

Long story short - the 110/120v rated PCB is "blown" due to plugging into wrong 220/240v power supply. A visual inspection showed a blown Varistor, which I bought a replacement from eBay and replaced/resolded it as per the photos below. Tested it with 120v power after this but still not working - no led lights nor any indication that power is flowing. I know how to do some soldering but in no way know how to "test" or troubleshoot a circuit board. This one seems no too complicated and I hope someone here can show me some way what else to check or which component to check (and how to check it) with a multi-meter, e.g. which component to test and what to expect. Thanks in advanced!

The two "ugly" component legs which I soldered on the top left corner is the new varistor (VR1) replacement. I bend it towards to next component in line as the original trace linking them seems to be broken. At this point, I have no clue what else to check or replace, although the blacken patch may give a hint. Still, I'm not educated enough to do further troubleshooting. Please help! Hans

 

[sagor1]

That little 4 legged device on the bottom appears to be a bridge rectifier. Odds are high it was blown as well.
The brown rectangular thing on the top of the board seems to be a 2.5A fuse of some sort, check that to see if it is open.

 

[hanschee]

The brown rectangular thing on the top of the board seems to be a 2.5A fuse of some sort, check that to see if it is open.

Yeah! That's open!
I didn't know it's a fuse until I do a search on "392 2.5A 250V" giving results on "Square Fuse".
I removed it just now and solder a wire across (temporary) and the air purifier works now!!!
I didn't know fuses come in "square"... LoL
Thank you very much sagor1