Re: Red vertical line on a led Acer pc monitor

On 5/15/2023 1:16 PM, MaxTheFast wrote:
> I've got this old lcd Acer x193w monitor in a home PC building. It's connected to my PC by a VGA cable and by an IEC cable to my UPS to be supplied.
> Today an 1 pixel wide red vertical line appeared on the right side of this monitor in correspondence of its on/off button as soon as I switched it on in; actually I've been pressing this button quite often along the years of usage, if it could be important.
> 
> This line doesn't appears in screenshot images but appears in BIOS environment and in both one of my OSs and it appears even if its VGA cable is disconnected from my PC so I think this issue doesn't deal with my PC components; anyway this is my cfg:
> - amd ryzen 2200g with Vega 8;
> - msi b450-a pro (bios V10.7; 2019-03-07);
> - 2x4gb hyperx predator @3200 cl16 (working @2400 by default)
> - wd black 1tb hdd;
> - corsair cx450 PSU;
> - no graphic card.
> 
> Honestly I don't know if this is a monitor electronic issue for sure or I've to consider other ways/things before trying to fix it, anyway I'd like to listen to your opinions.
> 
> What do you think the problem is and how to fix it (if possible)?

It's an issue with the panel used to build the monitor.
It's like a horizontal and vertical matrix that needs be driven, by ICs.

I don't have any good pictures to illustrate at the naked panel level.
They're usually covered with more metal.

You can see a ribbon cable goes into a panel subassembly here, and
there are two CCFL tube power wire feeds on the left of the photo.
CCFL tubes use sinewave drive ("pure" AC) and the cables are capacitively
coupled from the power board. When you see "foils" wrapped around
those cables, you endeavor to put the foils back the way you found them,
since at the 22pF level, those foils are "part of the circuit" from a
stray capacitance point of view. CCFL tubes draw around 3 watts of
power, at 700-1000VAC. Once the tube lights, the power source feeding it
drops the voltage to 700VAC or so.

The ribbon cable, has some sort of signal collection that needs to be
decoded into individual matrix drive signals. The ribbon cable then,
is most likely to have low-voltage digital signals on it.

    [Picture]

     https://i.postimg.cc/Df1XNm6K/x193w-back-opened.jpg

That's from a video:  https://www.youtube.com/watch?v=ih1msQ29WA8

The web information on LCD TV sets, they're pressing on stuff and
tapping on stuff. I don't know if that works on these smaller projects
or not. There is potentially a lot more at stake with a large TV,
giving the incentive to poke at it.

Quite some time ago, we were seeing pretty massive failures, like
200 random vertical lines on the panel malfunctioning. Almost like
"something is tearing away somewhere". That might be a problem at the
glass level. When you see just one defect, it could be an IC, and a
solid band of lines could be one IC driver. Whereas random lines could
be coming from some other root cause. Occasionally, it's the decoder
chip where the VGA signal comes in (but then the defect patterns
can contain 2D effects).

If I knew what to expect, I could warn you. I don't know if there
are elastomeric connectors underneath that metal surface or not.
Elastomeric compression conductors, was a scheme used on black and
white equipment status displays, for terminating a fair number of
electrical connections.

Pressing ("massaging") the front surface of an LCD panel, was for
interacting with the Thin Film Transistors (TFTs) that control individual
pixels. Since your problem is a vertical column, that does not suggest
massaging the front will work. It could be that pressing somewhere else
would help, but with that metal cover in the way, it's hard to say
what would work as a stimulus. Underneath the metal cover, the panel
is made of glass layers. And there could be materials bonded to the back of
the glass, for all I know.

    Paul