https://www.lkhrs.com/blog/2025/monitor-repair/

 

Fixing my monitor's power button

January 20, 2025

Turning one of my monitors vertical appeared to exacerbate an issue
with the power button to the point where it stopped working. I did my
first soldering job in years and was able to get it working again, so
I'm documenting it.

The power button on my LG 27UL500-W is a 4-direction control stick
with a center push action for power functions and navigating the OSD.
The center push action had always felt stiffer than on my other
monitor and sometimes it wouldn't register, but a stronger repeat
push made it work. Until Thursday, that is.

I went looking for workarounds. There's a number of macOS utilities
that will let you change the backlight brightness over DDC, but none
will let you change inputs or other settings. Same for LG's OnScreen
Control, which is a heinous excuse of a program that refused to
detect my monitors on macOS. On Windows it confused the rotation of
the vertical panel, leaving me with a comically sideways cursor on
the horizontal panel locked inside an invisible bounding box. I'm not
even sure why it was trying to handle rotation anyway, I didn't ask
it to. I uninstalled it in a rage.

The warranty expired a few years ago and I had nothing stopping me
from tearing the monitor apart. Multifunction buttons have burned me
in the past, as they're usually sealed shut inside a plastic box and
impossible to repair, but I figured I'd at least take a look and see
if I could get a replacement part off eBay.

Pulling the bezel off

First thing was to pull the rear housing off. There's one screw on
the back and then I had to slowly work my way around the front bezel,
unsnapping it as I went. The front bezel doesn't come off all the way
because the bottom has a couple screws attached to the metal frame
behind the power button.

Exposed back panel

With the rear housing off I had access to the power button
housing--it's the white plastic thing at the bottom center of the
panel. While the logic board and power components are covered by a
metal box, I must emphasize that even while unplugged it's still
possible to encounter spicy levels of current lurking inside the
capacitors in the power supply. Be careful if you try this at home.

Closer view of the power button housing

Power button removed

Power button housing rear view

I disconnected the power button module from the logic board and
pulled it out. I removed the cable and detached the circuit board
from the housing--it's attached with two little plastic clips straight
through the board.

Top view of the power button circuit board

With the circuit board out, the last part to remove to get to the
button itself was the plastic power button-shaped hat. The hat was
stuck on there real good, so I heated up my soldering iron and held
it in the air between the plastic hat and the top of the button for a
few seconds, and then I was able to pull it right off.

While my soldering iron was hot enough to get the hat off, it
struggled when it came to desoldering the button itself. I set it to
the max temp, waited a few minutes, and then pulled out my infrared
thermometer to take a ballpark reading. The soldering iron got
nowhere close to its set temp.

Infrared thermometer showing a reading of 223 degrees F

I checked the tip and it looked absolutely abysmal; I think it's the
original tip that came with the soldering iron when I bought it in
2016. I looked at ordering new tips, but then the intrusive what ifs
started popping up in my mind, and I fast-forwarded to a completely
ridiculous and improbable Catch-22 situation where I might need to
repair the soldering iron controller with a soldering iron. Okay
brain, checkmate, you win.

I remembered my pal Nathan recently wrote about the Pinecil V2. A
quick email confirmed he still liked his, so into the virtual cart it
went, along with new tips for the old one. Everything arrived Friday
afternoon.

Circuit board held in a Helping Hands soldering jig

It tickles me to know that there's an operating system aptly named
IronOS running on a tiny RISC-V processor in there. It has a cute
little display on the side that rotates when you switch hands! And
the temp readout is super helpful. But does it melt the extra tough
lead free solder they use for mass produced electronics?

Close up of the circuit board in the Helping Hands

Yes it does. Desoldering was still a tedious process though. I had
two pads to work on, and the golden tube that goes pop (I can't
remember the name) couldn't vacuum up the solder, so I slowly worked
the solder bead off the edge of the metal plate that wraps across the
top of the plastic button housing.

Button disassembled

Button with top off

Pulling off the metal plate revealed the inside of the button
housing, with a sheet of five little discs. Each of the discs are a
button whose function is similar to the freshness indicator on the
lid of a jam jar. I held my screwdriver near them and they leapt out
of the housing to stick to the tip.

Button sheets removed and laying on the desk

These button sheets are super thin and smaller than a pencil eraser.
Their size made them incredibly difficult to work with, and I quickly
discovered all my tools--even my tweezers--are magnetized, compounding
things. The middle disc in the sheet is for the malfunctioning push
action, and the surrounding four are for navigation.

And this is where I discovered the issue. The bottom left of the
photo above shows a discolored button sheet and a detached circle.
The circle was at the bottom of the stack of button sheets, in the
center where the malfunctioning push action is. Both the circle and
the button sheet that rests on top of it show signs of overheating
and corrosion, which at first I thought was from desoldering, but
then I saw the tiny wear marks on top of the discoloring. Which
combined with the fact that this button was acting up from the
beginning leads me to believe that it came from the factory like
this.

Inside of the button with the parts removed

I got the meter out to do continuity testing, and found that the
center contact point connected with the middle of the three pads
exiting the southwest side. I put the button sheets back in the same
way they came out and pushed the tip of one my meter leads directly
down the middle to simulate a button press, and had no continuity.

Photo of my cluttered workspace, with the meter out

Nothing a little DeOxIt and a q-tip can't solve though. After
cleaning the contacts on the bottom I restacked the button sheets
with one of the shinier sheets at the bottom and the discolored one
in the middle. I left out the detached circle part in the center
because it was going to be impossible to get it back in there. And
the scratchy beeps of my meter confirmed that we were making contact
again. Just to be sure, I put the plastic actuator and metal lid back
on and had Lauren press the button for me while I held the leads in
place.

Button after resoldering

Next, I resoldered the metal lid back on and brought the panel over
to do a quick test. Pushing the button brought up the OSD
immediately. Success!

Panel powered on and resting in a chair as I hold the button housing

The button is a lot less stiff to operate and I can change inputs
again. And my old soldering iron from 2016 appears to be working a
lot better with the new tips.

Tags: #Lg #Monitor #Electronics #Repair

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(c) Luke Harris

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