Components Breakdown When Under Full Load
Sometimes even if we have the best tester, we may miss out in finding out the bad component-why? because those components only breakdown when full voltage was applied on it. That means, your meter or tester may check it to be good but failed when the equipment was “on”. Semiconductors are prone to this kind of failures like diodes and transistors. So how are we going to solve this kind of problem? First you have to make sure that the problem was at the location and not in other section. For example if the main fuse always blow upon switched “On” and all of the components in the power and the secondary filter section checked to be okay then the only choice you have is to replace one by one the semiconductor in the primary section area. It could be a bridge rectifier or the big filter capacitor that had caused the fuse to blow when under full load.
However components breakdown when under full load was not that frequent. Sometimes whenever a badge of electronic equipment that uses the components that have problem, the whole badge would be affected. There was one model of dell 15″ LCD Monitor that have intermittent power blink problem. Sometimes the Monitor could work for whole day but the next day the power would blinks. When you switched of the power and “On” it again, sometimes the power may come back. The problem was in the fet 2n7000 located in the power section. All tester used tested good on this component yet it failed when under full load. The hardest thing to diagnose was that this component gave intermittent problem.
Since I’m very sure the power section is the main caused, i replaced one by one the semiconductors and eventually found this bad components. I had came across quite a number of it and i believe many similar model will be coming in for repair that have this intermittent power blink problem.