iMac 2019 LED Problem

[dudemansir]

I'm trying to understand what's happening to the LCD panel. Is this a backlight cable issue or is it the eDP ribbon connection? I took a look inside the panel and the backlight cable appears to be a little finicky and loose. Just gently checking it causes the screen to flicker or turn off. The only place I found the cable was some ebay seller in France, but I attached an example of the cable I believe is the issue.

The cable sends power to the LEDs on either side of the screen and both connection points are lit up and receiving power.

 

[PaulD-UK]

Do you have a 21.5" iMac?

The first picture shows a faulty (non-connected) backlight cable on the left side of the screen as viewed through the glass.

The second shows a detached backlight cable, from a 21.5" iMac.
When in use it is glued to the rear of the screen panel.

Where are you located?

 

[dudemansir]

Do you have a 21.5" iMac?

The first picture shows a faulty (non-connected) backlight cable on the left side of the screen as viewed through the glass.

The second shows a detached backlight cable, from a 21.5" iMac.
When in use it is glued to the rear of the screen panel.

Where are you located?

I figured it was the backlight. And yes I see it taped down around the back of the panel, connecting to the panel in the corners.

I'm in New York

 

[PaulD-UK]

That cable picture above looks like its from a 1080p 21.5" iMac.
The 4K iMacs have a backlight cable that doesn't have the double bends in the middle of the top run.
It goes straight from the L to the R across the screen.

Presumably your 2019 model is 4K?
If so that cable isn't the right one for it.

 

[dudemansir]

Do you have a 21.5" iMac?

The first picture shows a faulty (non-connected) backlight cable on the left side of the screen as viewed through the glass.

The second shows a detached backlight cable, from a 21.5" iMac.
When in use it is glued to the rear of the screen panel.

Where are you located?

I figured it was the backlight. And yes I see it taped down around the back of the panel, connecting to the panel in the corners.

I'm in New York

That cable picture above looks like its from a 1080p 21.5" iMac.
The 4K iMacs have a backlight cable that doesn't have the double bends in the middle of the top run.
It goes straight from the L to the R across the screen.

Presumable you 2019 model is 4K?
If so that cable isn't the right one for it.

27" 2019. 5k Model.

 

[dudemansir]

Paul...I see you were active in the DIY 5k thread. I didn't realize it was there before I posted this. I purchased a board (that looked reliable) off ebay and that darn backlight cable connection that everyone has mentioned was not a great fit. Perhaps the first connection damaged the cable connected to the panel (didn't get video) and after removing and reconnecting (got video) with loss to one side.

 

[PaulD-UK]

So your backlight problem might be the plug connection to the B/L cable not connecting to one side, or it might be the actual cable is damaged.

Or it might be the B/L output connection on your video board might not be plugged the right way.

Some of the cheaper video boards have mismatching plugs and sockets…

 

[dudemansir]

So your backlight problem might be the plug connection to the B/L cable not connecting to one side, or it might be the actual cable is damaged.

Or it might be the B/L output connection on your video board might not be plugged the right way.

Some of the cheaper video boards have mismatching plugs and sockets…

The only thing I touched was the actual cable coming out of the panel. That connector that has the nervous force together point.

Should I try a new cable? And honestly where would I even get one? Every search I do points to that eDP ribbon at the top center of the panel

 

[PaulD-UK]

Shine a torch at the black side of the screen.
If there is an image there then it’s the B/L that has failed.
If there is no sign of an image then it’s an eDP video problem.
eDP problems are usually hard-edged not gradual like your original polic.

Chose a nice bold screen image to try this.

 

[dudemansir]

I just took another look using the board that I had. I was able to see, faintly, a browser window i was moving around on the screen. But some weird ghosting movement. Occasional flickering if I move the screen a little. I have some images and videos. Hope imgur is ok. In addition this is the power supply I'm using which fell within the recommended 12v 5a-7a
Power Supply

imgur link

https://imgur.com/a/iMYtxs9

 

[PaulD-UK]

In the first pic you posted the left of the screen was dark.
With your video I can't tell which side is the problem.

Which board do you have?

 

[dudemansir]

In the first pic you posted the left of the screen was dark.
With your video I can't tell which side is the problem.

Which board do you have?

Sorry the camera was closer than I wanted.

The left side is def the problem. I attached another photo. That is a full screen image of a blue sky with clouds. Any ghosting on the left is there from when the lighting brightens a little for a second. But just moving the panel a little makes the backlight shift a bit. All def localized on the left side. Some of the videos in the last link showed how there is a strange bleeding or ghosting happening.

 

[PaulD-UK]

That looks like the backlight has failed on the left.
Whether its the cable to the backlight somewhere from the new video board to the screen, or whether its the screen backlight that has failed is not clear.
Has the screen panel been involved in any damage?
I've not seen that jagged edge between the light and dark side before, and nothing should move as you move the screen.

But the main eDP cable from the board to the screen may also be part of the problem, if there is the slightest bit of dust on the 60 pin connections, or if any of the connectors are damaged.

Did the board come straight from a Chinese vendor?

Edit. It looks like something is moving around inside the screen, masking the backlight, or the backlight cable is intermittently partly shorting some of the wires....
Definitely never seen that before.

Is the backlight cable firmly stuck down inside or could it be flopping around?

 

[dudemansir]

Yeah there was like nothing wrong with the panel prior to starting this so the backlight itself failing is just crazy to me. There wasn't any damage as far as I know. At this point the screen results are the same whether on this new board, or connected to the apple hardware. Which is why I was thinking the backlight cable.

This is the board I ordered. I was just following the few youtube videos I had seen on the topic.
Ebay Board

Seeing as how there are so many possibilities for what could possibly be wrong I guess it's pretty much a wash at this point?

 

[PaulD-UK]

That's a JRY-W9CUHD-AA1 board.

Is your backlight cable plugged into the board so the two red wires are connected to the middle two pins of the outer socket?
The 6 pins go – – + + – – and if either of the two red wires are not plugged into pins 3 and 4 HALF your backlight won't be receiving any power.

The other small 2 pin socket inside the the 6 pin socket should only have 5 black wires going to the left pin of the 2.
The pin near the other socket should be unconnected as the pins go – +.

Your cable(s) may be different to the picture from your vendor, but you can check the red wires should only go to a + pin.

The long pin connection to the screen backlight cable is – – – – – + – – – – – +, with the last + wire going to a grey wire in the backlight cable if you monitor's B/L cable isn't all black wires.

 

[dudemansir]

That's a JRY-W9CUHD-AA1 board.

Is your backlight cable plugged into the board so the two red wires are connected to the middle two pins of the outer socket?
The 6 pins go – – + + – – and if either of the two red wires are not plugged into pins 3 and 4 HALF your backlight won't be receiving any power.

View attachment 2414062

The other small 2 pin socket inside the the 6 pin socket should only have 5 black wires going to the left pin of the 2.
The pin near the other socket should be unconnected as the pins go – +.

Your cable(s) may be different to the picture from your vendor, but you can check the red wires should only go to a + pin.

The long pin connection to the screen backlight cable is – – – – – + – – – – – +, with the last + wire going to a grey wire in the backlight cable if you monitor's B/L cable isn't all black wires.

View attachment 2414060

That's a JRY-W9CUHD-AA1 board.

Is your backlight cable plugged into the board so the two red wires are connected to the middle two pins of the outer socket?
The 6 pins go – – + + – – and if either of the two red wires are not plugged into pins 3 and 4 HALF your backlight won't be receiving any power.

View attachment 2414062

The other small 2 pin socket inside the the 6 pin socket should only have 5 black wires going to the left pin of the 2.
The pin near the other socket should be unconnected as the pins go – +.

Your cable(s) may be different to the picture from your vendor, but you can check the red wires should only go to a + pin.

The long pin connection to the screen backlight cable is – – – – – + – – – – – +, with the last + wire going to a grey wire in the backlight cable if you monitor's B/L cable isn't all black wires.

View attachment 2414060

The backlight cable IS all black wires. I attached pics of my board and the attached wires.

 

[PaulD-UK]

It looks like your B/L 12 pin plug is the wrong way round connected to the screen panel B/L cable?

The 3 slightly raised circles should be facing you when the outer red wire is to the right.
Like in the 2nd picture I posted.

 

[dudemansir]

ahhh I see. Excellent to know. However the problem persists even when connected to the mac hardware. so don't think that's the issue.

 

[PaulD-UK]

As you first thought it seems the panel’s backlight cable is not right.
Or the actual screen panel… 🙁

 

[dudemansir]

Where do you even find that cable? I can't seem to find it anywhere online.

And if it's the panel...the panel is done for right? There's no going in there and replacing LEDs or anything like that right?

 

[PaulD-UK]

You would have to take a B/L cable off a broken 2019/20 screen panel.
Earlier year iMac screens would fit for the JRY board but not your 2019 logic board.
Broken screens are not repairable…