Have you encounter before preset (potentiometer) problem in electronic boards? As for me Yes, i experienced an open circuited preset in the switch mode power supply causing the power to blink. First i did not suspect it was the preset because normally it was quite reliable but after checking all of the electronic components (beside preset) and could not locate any bad one, i turned to preset. Guess what? the preset have an open circuit! Normally whenever preset have problem it would just cause erratic problem like display shaking and intermittent problem and i didn’t suspect it to be totally open circuit. Well, in electronic repair, anything could happen to electronic components. The electronic components could breakdown when under full load, sometime work and sometimes don’t, total failure and etc. So in the future if you want to check all electronic components in any circuit boards make sure you really check all of the components in it (that particular circuit). If you miss one it could be that component that cause the electronic equipment do not function.