How-To Repair a Desktop LCD with Bad Capacitors
January 17, 2008 By Jeremy Brock
Desktop LCD monitors fail for a variety of reasons, the most common being bad electrolytic capacitors. If you are willing to invest the time you can fix your LCD for a few dollars in parts. For this demonstration I’m using an IBM ThinkVision 6636-AB1 however the same techniques apply to most desktop LCD Monitors.
Disclaimer:
A+ Perfect Computers, LLC, is not responsible for any damages to your device, person, or property. Computer, Laptop, or LCD disassembly and part installation is at your own risk. This Guide offers only suggestions for taking apart your device. The components inside your device are highly sensitive. Always ground yourself by using an ESD wrist strap or by touching a metal object while handling sensitive electronics.
- Symptoms:
- No Picture on Screen
- LCD displays picture briefly then turns off
- Tools:
- Soldering Iron
- Desoldering Station or Solder Sucker
- Phillips Head Screw Driver
- Spudger (Available Here and Here)
This LCD would turn on for a second then shut off. These symptoms are usually caused by a bad CCFL light or inverter board. After opening the LCD I did a visual inspection of the PCB looking for any dark areas, damaged IC’s or bad filter capacitors. The top of filter capacitors should be flat, bulging or leaking is an easy way to detect a failing capacitor. If available an ESR meter can be used to validate the capacitor is failing.
In this instance there are three bulging capacitors. Finding replacement LCD components can be tricky however replacement capacitors can be purchased at most electronic part stores. In this case we use mouser.com
To order capacitors enter the Capacitance and Voltage rating into the Capacitor Product Filter on Mouser. Look for the capacitor with the smallest diameter and length, prioritizing a smaller diameter over length if necessary.
Click on an image for a larger picture
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Remove the mount (not shown) and housing screws. The housing screws are usually located on corners of the LCD however they may be hidden under a rubber insert or sticker. |
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LCD's use plastic clips or snaps to hold the housing together. Use a spudger to gently pry the housing apart. Avoid using a metal screw driver as it will damage the plastic. |
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Remove the protective cover. Depending on the design you may need to slide the protective cover off once the screws are removed. |
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On this model the inverter board and power supply are on the same board 1. LCD CCFL Backlight Connectors |
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The top of an electrolytic capacitor should be flat. You can visually inspect capacitors by looking for a bulging top or dry brown crusty substance leaking from the capacitor. |
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Electrolytic capacitors have a solid line or dash going down one side for negative polarity. Installing an Electrolytic capacitor backwards can damage it so make note of the polarity relative to the board then desolder it |
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Make note of the capacity and voltage, in this case the 1000uf 16V and 470uf 16V (not shown) capacitors were bad. |
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Next solder the new capacitors in place making sure the polarity is correct. After soldering reassemble and test the monitor |
My IBM ThinkVision had the symptoms as described here. IBM told me that it was impossible to fix and I had to buy a new one. This does not make sense as the picture still is visible in a flash, before turning black. I am not a technical person, but after reading this article, I decide to take up the challenge. After inspecting the inverter board's capacitors, I could not se anything strange. But after more close inspection, I found one Capacitor on the bottom, the rubber part, I found out later (black), was pushed out and this was difficult to see. The top was still fine. I bought the tools and just started, never have done this before. I replaced the one capacitor, assembled and switched on. Done. Works perfectly again. Took me less than 30 minutes at a fraction cost. Thanks for the article, best ever.
My work gave me two viewsonic vx715 monitors that had symptoms of lighting up for a second or two and then the screen would go black. Thanks to this article I opened it up and found a very slightly bulging top on one of the 16v 1000uf capacitors. Actually it was the same capacitor on each monitor. I replaced it and it has been working perfectly ever since. Thank you very much Jeremy Brock, for such an informative article.
I found this article to be very useful in helping me with the capacitors on the inverter board. I found 3 bulging capacitors but went ahead and replaced all except for a 100uF,450v capacitor at the power inlet point. Replaced 5 - 470uF,25v, 105c and 4 - 220uF,25v, 105c. This did not correct the problem. The monitor flashed a beautiful screen for about a second then off. Can push the input key and screen flashed for another second. Will do this all day. Have changed resolution and refresh to every available setting with same results as above. I am pulling my hair out.
Problem solved. Turned out to be "dry" solder joints at the inverters. Re-heated joints & a minute touch of solder and the lcd works great!!!