Avi's page for LG flickering LCD monitor fix

How did I fixed LG-1970HR/HQ LG-1770HR/HQ LG-L1780U/UN LCD flickering monitor?


LG monitor fix0

LG monitor fix0




My LG-1970HR monitor started to flicker on a random basis.
Searching for a fix I have learned that this fault is well known and can be linked to any of the following:
1. Power supply
2. Inverter PCB
3. LCD lamp

This monitor power supply is an external component and it is the easiest one to start with.
In this guide I’ll show you how to fix the power supply that is the common cause of the flickering fault.

This fix is ONLY for those with electronics and mechanical knowledge and skills.

Warning:
This fix is NOT recommended by me nor by LG and will void product warranty !
If you follow this fix, you do it on your own risk ! !


This is the model of the power supply this fix is dealing with
My LG-1970HR monitor and probably other models as well, uses 42W 12V 3.5A power adapter
model DSA-0421S-12 which is an external unit.
LG monitor fix1

In order to fix this power supply we need to open it, replace some components and do some soldering work.
First check that you have unplugged the power adapter from the mains
and that you have removed the AC power cord from it.
Note: this unit has capacitors in it so be very careful not to touch it to avoid getting electric shock.

1. Take the 2 rubber feet off and unscrew the 2 screws found under the feet.
LG monitor fix2

2. Open the power adapter case in a diagonal movement.
First lift the edge where the 2 screws were located and then with a help of screwdriver and some pressure
release the 2 snaps that hold the other side.
LG monitor fix3

3. This is how the snap looks like
LG monitor fix4

4. Remove the cover and observe the condition of the components, especially capacitors.
In my case it was obvious that 2 capacitors were bulged/blown,
a residue transfer was also found on the top cover which helped confirming this diagnosis.
These capacitors are identical -
1000uF 16V.
LG monitor fix5

5. In order to replace the capacitors take out (lift) the electronics block and turn it upside down.
Unsolder the shield PCB on one side to gain access to the capacitors soldering points.
LG monitor fix6

6. Now you have access to the PCB print side. Remove some of the thermal glue that hides one of the capacitor legs.
LG monitor fix7

7. Unsolder and remove the defective capacitors.

Replace the 2 capacitors with same type.
Pay attention to polarity!
Capacitor has polarity and you should replace each one to same position on the PCB keeping same polarity.
Both capacitors minus (-) pole are facing the inside of the PCB as seen on photo.
LG monitor fix8

8. When done soldering the new capacitors, cut excess legs and start assemble the power supply.
LG monitor fix9



Assembly - assemble all parts in reverse order to what is listed above.

A. Return the shield PCB and solder its wire.
B. Assemble the electronics block and close the case. Start with the side with the snaps.
C. Reconnect the power cable and connect the DC connector to the monitor

Voila - start using your monitor. You have fixed your power flickering fault.

 

Have fun and enjoy your LG monitor.

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Need more help to fix your appliances? View my other fix/repair guides





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LG monitor fix0


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Last update: Oct. 08, 2013

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