Acer AL511 LCD Monitor Repair- Intermittent No Power

The complain for the ACER AL511 LCD Monitor was intermittent no power. That’s mean when the front power button was pressed the power would sometime comes and sometime no response at all. When there is power the display would appear and it worked perfectly fine until when you switch the power off and then switch it on again. Most of the time it will work but at sometimes the power LED just don’t light. My first impression was the defective power push button micro switch.

If the intermittent no power problem happens in the CRT Monitor, then most probably it is the start up circuit resistors fault. The start up resistors value may have gone too high causing it to have intermittent no power symptom. It could also be a defective on/off power switch too.

Let’s get back to this ACER AL511 LCD Monitor problem. The reason I don’t suspect start up resistors fault in this ACER AL511 LCD Monitor was because the power on/off switch signal was derived from the CPU. Unless you talk about LCD Monitor that used mechanical on/off switch where it have the same function as the CRT type of Monitors.

Opening up the cover was very easy and you can clearly see the three boards i.e. the main board, power/inverter board and the control panel board. The LCD controller board was located at the back and beneath the metal casing. Using my analog meter set to X 1 ohm to check on the micro switches at the control panel board found two of them to have intermittent problem. Sometimes the meter’s pointer would kick when the button was pressed and sometimes it won’t.

Next is to solder out the faulty micro switches and replaced them with a known good one. After the soldering job was done, I checked on the power/inverter board just in case if there are any dry joints that need fresh solder. Well, it seems that only the microswitches have problem and now the power button was pressed and the display immediately appeared. I deliberately pressed many times the power button just to check if the intermittent problem had been solved. Yes, the display and power comes whenever the button was pressed. In the above case, it proved that LCD Monitor problem can be caused by a minor fault and it is not necessary must be a major problem.