Before you discard your defective LCD monitor, try to do a visual check on all electrolytic capacitors.. chances are that it may only cost you few dollars to replace these defective capacitor than buying a new monitor.
Why do capacitor bulge? One of the most common failures in LCD monitor and TVs is the bulging capacitor(s).
Bulging Capacitors and how to spot them.. As time goes the capacitor bulge or expand, because the inferior electrolyte dries up. The bulge on the top portion of the capacitor indicates that it burst or leaked. If you find that top section of a capacitor is bulging then most likely it is a good candidate for replacement. In actual practice you will find not only one bulging capacitor but some boards may have up to 8-10 leaky capacitors.
But not all capacitors will bulge, swell, and burst. They can fail and you would never know by looking at them. In older days, technicians have to remove each single component from the board just to test using an analog tester. In the case of a capacitor, both legs are connected to the (-) and (+) terminal of the analog tester and set the selector switch to ohm range. The pointer will deflect up to zero ohms as the capacitor charged up and goes back to infinity as it discharges. The process is of testing using an analog has been discourage because it does not reflect the actual value of capacitance. But thanks to the advent of newer types of testers, which can provide correct parameter values. One of these device-testers is an LCR tester, that stands for inductance, capacitance, resistance tester.
I use my LCR tester to test correct capacitance value of a capacitor in a circuit board. Aside from the bulging capacitors, which we already conclude to be defective, another visual indication of a bad capacitor is the discoloration of the it’s surrounding area. If the body-case of a capacitor looks grayish or brownish then I would remove one of the legs and do a capacitance test.
What are the effects of bad capacitor in an LCD monitor:
- most LCD monitors that have bad capacitor(s) will have no display or dark-screen. The power LED indicator will light up for a moment but does not display anything on the screen
- some monitors will turn power on for about few seconds then off instantly.
- other monitors will light the display (screen) a moment then turns off display for few seconds.
If you experienced anyone of the above then mostly likely the capacitor(s) need to be replaced.