How can I fix my LCD monitor's loose connection?

May 6, 2009 7:53 AM

My LCD monitor is flickering, scrolling, and generally behaving strangely, almost certainly due to a loose connection. Can I fix it?

Over the last couple months, my 24" Soyo LCD monitor has been exhibiting strange behavior. It will vary in brightness, scroll horizontally, display jagged lines and exhibit other strange behavior. At first, wiggling the DVI cable would alleviate the problem; now I have to physically shake the monitor. I've also used both the monitor's VGA and DVI inputs and it exhibits identical behavior. This all points towards a loose connection inside the monitor. Is it possible to identify and/or fix this problem myself?

I started to poke around myself, but after removing the plastic housing I was daunted by the next layer of metal casing. Even if the odds of me being able to fix it are low, I'd still like to give it a shot before I have to buy a new one.

posted by christonabike to technology (6 comments total)

Congrats on troubleshooting it to the point of an internal connection.

It is totally doable, if it is indeed a loose connection, but you must exercise a little caution.

First, and obviously, unplug the monitor. The "second layer" of metal you see is electromagnetic shielding for the underlying electronics. It's more for the protection of your other electronics than anything.

To remove this shielding, you will need a screwdriver (most of my LCDs have been Phillips-head screws) and a small pliers. You need the pliers because this shielding layer is usually held on with the little nuts that are left and right of your VGA and DVI connectors.

Grab a piece of paper, draw a rough sketch of the monitor's insides on it. Then place the screws on the piece of paper so you don't forget where they go. When all the screws are removed, remove the shield, too.

Now, inside the shield, you are probably looking at two separate boards. One is the "motherboard" with signal processing. You can identify it by the VGA and DVI ins going to this board. It will be connected through some kind of connector (or perhaps piggybacked under) a second board. This board will have some coil-looking things on it. It is the power supply and inverter board. It is identifiable by the power connector on it. It is dangerous, so don't touch any contacts on it bare-handed. You may have to remove the power supply board to get access to the motherboard.

When you finally have access to the motherboard, you'll see a wide, flat cable that extends from it to the top or bottom of the LCD. This is the cable you are looking for. It is exceedingly delicate and easy to screw up. It is most likely stuck down with orange (kapton) tape. Don't pull it up if you don't have to.

BTW, if you can see this cable w/o removing the power supply, DON'T REMOVE THE POWER SUPPLY kthx

This cable is the likely source of your problem. You will have to un-and-re-connect it where it connects to the mainboard (only there; the other side is connected to the LCD glass and cannot be unconnected). The connector that it plugs into is usually a "zero insertion force" connector, which means that the cable doesn't plug into it like headphones into a music player. Rather, the flat end of the cable has many tiny contacts on it (something like an SD card) and it is laid into the connector and there is a small part of the connector which snaps over it. In fact, it is a little bit like how RAM is mounted into a computer, if you've ever done that. I suggest you google "zif connector" to find out more about these.

Those connectors have an insertion/uninsertion life of about 10x... so don't plug/unplug too much. Try removing and reseating it once, then partially reassemble everything (leaving the shield and the back of the case off) and try your display again. If it works, congrats.

If you blew it up, it isn't my fault, but at least you learned something.
posted by fake at 8:56 AM on May 6

I'm going to try following those steps in a few minutes.
posted by christonabike at 11:07 AM on May 6

Following fake's instructions, I successfully removed the electromagnetic shielding and found the the described cable that attaches the signal processing motherboard to the LCD screen. In my case, the connector was covered in glue, so I just pushed on it and reassembled the monitor. It's working now, but in the past successful wiggles/shakes would sometimes make the monitor last anywhere from a few hours to a few weeks, so I'm not calling this a complete success just yet.

Some other notes, for future folks who may want to dissemble their LCDs:

On my LCD, both the power supply board and signal processing board were mounted to the top of the electromagnetic shielding. That is, when I removed the shielding, the boards were still attached to the shielding from the top of the shielding down (hope this makes sense).

My LCD had a vast amount of zip ties and metallic tape, much of which had to be removed to access the necessary components. Most of this wasn't replaced. I'd still like to know the purpose of the metallic tape.

In addition to noting the screw placement on your sketch, I also advise noting the wire colors or other notable characteristics of any cables that could be ambiguously connected.

There were some connectors that I was unable to remove even with significant force. One of these was the button that seemed to go from the power button to the signal processing board. Is there a trick to removing these?

fake, your instructions were very clear and useful, so I'm gonna mark it a best answer.
posted by christonabike at 12:30 PM on May 6 [1 favorite has favorites]

One of these was the button that seemed to -> One of these was a cable that seemed to
posted by christonabike at 12:32 PM on May 6

KICK ASS. I'm so glad you fixed your display! (to the degree that it is fixed, anyway).

Metallic tape covers gaps in the shielding. Basically, if a tin or copper cover doesn't mate cleanly with another, they just put tape over the gap and that stops RF leakage.

It's rare but not unheard of to see zipties everywhere. Hope you are now comfortable with hackin' through them.

Great advice regarding wire colors. One trick re:wire placement is to use a permanent marker to mark up the connector and the plug that goes inside it. Usually the jacks are white, and the plug, too. So I just stroke a permanent marker across them and then if the marks line up later, I know I have it right.

Regarding the connectors that didn't come out, there are occasionally things that look like connectors but are actually soldered to the board. If you look closely, they'll just be one piece of plastic. If they clearly have two parts, you'll find that there are little, square things that you have to kind of pry back to disengage the connector. There are about a jillion varieties of these things, so I can't really be more specific there. Still, I would have expected the cable going to the power button board to come free. That's odd.

Really glad I could help. Thanks for coming back with your notes!
posted by fake at 11:08 AM on May 17

So I just stroke a permanent marker across them

while they are plugged together, that is.
posted by fake at 11:09 AM on May 17