My dewalt dws780 doesnt sound right and the brake stopped working .what part needs replacing

Check to make sure the new blade is all the way onto the back collar and centered.

Have it trepaired under warranty.
https://servicenet.dewalt.com/documents/English/Instruction%20Manual/N466020,DWS780.pdf

Have you checked the manual. My Dewalt Dws780 was not turning on, then I checked the manual and able to start it. There was some sort of plug issue with my saw but thankfully it sorted out quickly. I got this saw from this video recommendation.

Curious if you got an answer? My Model 36-230 miter saw is locked in doen position and I can't get it unlocked and upright.

sure
you need to test motor brush, switch , field coil

the brake is contained in the switch, also check the brushes while you are at it.

first make sure brushes are not worn out and if not then replace the switch. the brake is contained in it to throw a short thru the motor when trigger released to stop drill. You can find a breakdown for this tool at Dewaltservicenet.com

this is a replaceable part and they do wear out

hi there remove and check if the brake pad indicater may be sticking out or may stone stuck on it hope that helps pliz do send me the rating

yes this is normal the spark keeps motor from stalling out by taking away the friction spark by making own spark
the clunk is the drill brake so you dont brake your hand when screw goes in all the way unlike old drills that kept going even when your hand was attached to it