large blobs

About every 90 minutes I get a really large blob on my prints. Its so large the next pass knocks it off the print and the print turns out ok. It leaves a small burn mark like inside the letter B in the pic. I upgraded the board from cr10 to cr10s and added the creality aluminum extruder. Im using the chepclub profiles. Any ideas how to correct this?

There are tons of questions on this forum with no replies . It had something to do with my hotend so i bought a new hotend for $25 and now its printing fine.