HELP! Heated Bed Temp. kept raising to 100 degree C

Hi All,

Today I tried to play with ABS. I set the heated bed temp to 80 degree C. After a while, temp started shooting over the set temp to 100 degree C. Finally, the printing stopped (i guessed due to overheat).

At this moment, I lost the control of the heated bed. I set the temp at 30 degree C when printing PLA, but the temp continued raising. The override temp on the Controls didn't work. Right now, I'm using a personal fan to cool the heated bed to prevent it to hit 100 C.

Did I burn any components on the RAMP board? If yes, which one?

P.S. I just finished printing a part in PLA. Temp of heated bed continues to raise even printing is completed.

Thanks,
Phat