Repair a Desktop LCD with Bad Capacitors | Electronics Repairguide Collection


Repair a Desktop LCD with Bad Capacitors

How-To Repair a Desktop LCD with Bad Capacitors

Source: http://www.aplusperfect.com/articles/lcd_capacitor_repair


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

Back of LCD Monitor
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.
Open Housing 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.
Remove Protective Cover Remove the protective cover. Depending on the design you may need to slide the protective cover off once the screws are removed.
Picture of Inverter Board On this model the inverter board and power supply are on the same board
1. LCD CCFL Backlight Connectors
2. LCD Ribbon
3. Analog to Digital Converter
4. Power Supply
5. Inverter Board
Bad Capacitors 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.
Desolder Capacitors 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
compare capacitors Make note of the capacity and voltage, in this case the 1000uf 16V and 470uf 16V (not shown) capacitors were bad.
solder new capacitors Next solder the new capacitors in place making sure the polarity is correct. After soldering reassemble and test the monitor
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