Samsung Galaxy series

Samsung galaxy S4/note 4

boot looping stuck at Samsung or carrier logo - normally the nandchip solder balls popped off the board ,you can reflow or simply push down on were the chip is on the board to temporarily make contact to retrieve data if needed

Samsung galaxy S5 /note 5

suffers from the same issues as the 4 and it can normally be solved the same way

Samsung Galaxy s8/s8+/note8

boot looping - not charging random turn offs, bad PMIC its a common issue on the entire 8 series, could also be a battery

Samsung s9/9+

boot looping or randomly turning off- most likely a bad finger print scanner ( certain finger print number batches had this issue mainly the first made ones) Could also be a battery