So, I have been printing in PLA for months. No problems. I tried switching to ABS 220'c without using the Heated bed. Got some pretty crappy trial prints. Tried out the heated bed, and it seems to work fine, none of the problems other people have, though I only take it to 80'c. I try printing with the heat bed at 80'c and the print head at 220'c and the print head drops temperature. Frustrated as I cant figure out why, I switch back to PLA and still my print head wont hold temp at 190'c. I do some fault finding and discover I can hold about 150'c all day but anything above 160'c and the print head stops heating and drops to room temp. **** around for a while to reset the printer before i can get the hot end to heat after each fail. So, either what causes this or how do I fix it.