Saturday, March 17, 2007

LCD backlight repair and troubleshooting

How to tell if you’re LCD is dead or just needs a new bulb?

So you’ve had that LCD monitor or laptop for a few years and it has been working like a charm. Great, until one day, you see red. The sky is red, faces are red, you get the picture (or maybe not) Maybe you get no picture at all, or the picture shows up when it feels like it. What to do? Don’t chuck it out - just yet!

The quick and dirty behind LCD panel construction is basically three components. The LCD panel itself, or the glass. The CCFL, or Cold Cathode Fluorescent Lamp, which is commonly called a backlight, and last, the inverter. The inverter supplies power to the backlight which in turn provides lighting to the lcd glass panel. The lcd and backlight are constructed together and sealed.

When a backlight is about to go, your display will usually have a reddish tinge to it. This is most evident when powering the laptop on. The red tinge may disappear as the backlight warms up and eventually operate normally. This means that one day, you will have no backlight. The image will be very faint on the lcd glass, and under the right lighting, may be slightly visible. To verify this, you will need an external monitor to plug into the laptop. Toggle your display from the laptop to the external by pressing Function key (FN) and either F4, F5, or F7 key, one or two times. Each manufacturer has their own function combination, so please check first. Usually you will see a key on the keyboard, in the function key rows that has a picture or a monitor on it.

Toggling the display to the external monitor will verify that the problem is not with your laptop video card. If the picture is fine, then the problem is either the backlight or the inverter. If you have a full size LCD and wan to verify where the problem, is, you will have to get another monitor.

If an inverter is going to malfunction, it usually goes without warning. If a backlight malfunctions, it typically gives some sort of warning beforehand. Hence the reddish tinge. In any case, replacing a backlight or inverter is not for the beginner. Where laptops are concerned, the inverter is located just below the lcd panel itself, on the actual laptop lid. Inverter’s are fairly inexpensive and can be easily found on ebay. You may search the model of the laptop, or if possible get the part number off the inverter itself, and search that. Expect to pay about $15 – 40 US, plus shipping.

Replacing the backlight is another procedure completely. Unfortunately, determining exactly what parts needs replacing (backlight or inverter) is not an exact science. Backlights are cheaper than inverters, but much harder to replace. Inverters cost more, but can be done in a few minutes. Backlights are not easy to replace by any means, and they are to be dealt with extreme caution. They contain mercury (contact your local authority for proper disposal information) . It requires complete removal and disassembly of the lcd panel. If you manage to gain access to the backlight, you can simply measure its distance from end to end (glass start to glass end) in millimeters, and its relative thickness, again in mm. This can then be used to order a new backlight. Backlights can be ordered from and other sources. They run about $9.95 US, plus shipping.