The complaint of this 17″ Compaq LCD Monitor was shutdown after few seconds to few minutes. That means the display sometime will shutdown in few seconds while sometime it will shutdown in couple of minutes. When there is a display the picture worked perfectly good until it shutdown. The first thing one would normally suspect is the defective backlight. For your information, a bad or a weak backlight can cause such problem and dry joints may also contribute to the cause of the fault.
Since I have a spare backlight, I swapped the LCD backlight with the working one. It is easy to do it, just remove the existing backlight connector and connect the good backlight connector to it. I have tested one by one the backlight and the result was the LCD Monitor still shutdown intermittently. This has proved both of the LCD Monitor backlights are okay! So now my concentration is looking for any dry joints in the LCD Monitor.
I put back all the internal metal casing like original except the main cover and switch “ON” the LCD Monitor. While at my left hand holding the LCD Monitor, my right hand holding the shaft of the screw driver, I began to gently knock on the LCD Monitor internal metal casing with the handle of the screw driver. The moment I ‘hit’ it, the LCD Monitor went straight into shutdown. Wow! From the test I believe you would have known what is the cause of the LCD shutdown-it was dry joint.
Opening up the casing again, you can clearly see three boards i.e. the power/inverter board, audio board and the Main board. I only suspect the power/inverter board because this is the board that controls the backlights. What I did was resoldered all the components in the inverter area except the SMD components because SMD components rarely have dry joints.
When I power “On” the LCD Monitor and hit it with the handle of the screw driver, the Monitor again went into shutdown. I told myself “it can’t be” but anyway I have a very high confident that the fault must be in the inverter area and not in Main board or power board. Next, I carefully hold the LCD panel and use a test pen to lift up the corner of the inverter board and power “On” the Monitor. Guess what happen? The Monitor did not shut down even though I ‘hit’ a little bit hard on the metal casing. This again proved that the problem is somewhere in the inverter area.
I opened up again the metal casing and carefully scanned through all of the components in the inverter area-it look like I have already applied fresh solder to it. It was only the feedback circuit that have SMD components that I haven’t solder. I used a magnifier glass to check if there are any dry joints in all of the feedback components but I don’t see any. I went ahead to resolder all of the SMD components in the feedback circuit and power “On” the Monitor. To my surprised, the LCD Monitor no more shutting down no matter which way or how I tapped the LCD Monitor with the handle of the screwdriver. I put the LCD Monitor for many hours of burn in test and it just worked great. I have sent back the LCD Monitor to my customer and till now after couples of days there is no call from my customer.
Conclusion – Do not overlooks the dry joints in SMD components. Every part in the electronic board can be a suspect. Hope from this article you can get some ideas about solving intermittent problem in LCD Monitor.
Post time: 11-14-2017