DIY 5k Monitor - success :-)

[DaveF]

I'm seeing severe ghosting scrolling web pages like this one with high contrast (e.g. black text on white background). That never happened with the native iMac. Is there a setting to change in the R1811 menu? Or do I just live with this, a consequence of a budget solution over buying an actual Apple standalone 5K monitor?

 

[PaulD-UK]

@DaveF No I'm not seeing that, at all.
I went to an Apple Store to check over a Studio Display, and to me, it didn't see any different/better than my R1811 conversion.
The only difference with my conversion is I put a brand new iMac Pro screen in my monitor, but if you are using a 2017 iMac screen, it should perform the same...

That's checking in Light mode, as I normally use Dark mode, as the sharpness of the text is even more impressive.
And also I've got Better Display (free) installed to control brightness, so I'm probably viewing a less bright screen.
I can't work at more than about 60% brightness, unless I'm watching a move shot in the fashionable HDR 'dark mode.'

You certainly can change the settings in the Menu so set the screen to perform as you want.
Monitor Control is alternative control software.
EDIT: The Eizo Monitor Test webpage is a good way of testing for any screen defects, including blurred motion.

 

[traxap]

@traxap - I'm very interested in your method of connecting the PSU to the SA1. I am strongly considering the same thing once I get the components to do my conversion (also a 2017 iMac). Which male connector on the SA1 board are you connecting to and how are you adapting the PSU connector to it? Or are you soldering directly to the pins on the back of the board?

SubDriver - I will post pictures tomorrow. I will use the connectors shown in the picture below. Most likely splice and solder wires to the male power supply plug. I got the idea from post #1409. He did a nice job.

Thanks.

 

[PaulD-UK]

@traxap Let us know here how it performs with 12 volts, as other people are asking about boards that perform well with 12v.

 

[traxap]

@traxap Let us know here how it performs with 12 volts, as other people are asking about boards that perform well with 12v.

Sure @PaulD-UK. I will definitely report back.

 

[DaveF]

@DaveF No I'm not seeing that, at all.
I went to an Apple Store to check over a Studio Display, and to me, it didn't see any different/better than my R1811 conversion.
The only difference with my conversion is I put a brand new iMac Pro screen in my monitor, but if you are using a 2017 iMac screen, it should perform the same...

That's checking in Light mode, as I normally use Dark mode, as the sharpness of the text is even more impressive.
And also I've got Better Display (free) installed to control brightness, so I'm probably viewing a less bright screen.
I can't work at more than about 60% brightness, unless I'm watching a move shot in the fashionable HDR 'dark mode.'

You certainly can change the settings in the Menu so set the screen to perform as you want.
Monitor Control is alternative control software.
EDIT: The Eizo Monitor Test webpage is a good way of testing for any screen defects, including blurred motion.

I’m using MonitorControl because it also gives me volume control. I tried BetterDisplay but won’t do audio / volume control (reports that function is unavailable to it).

I’m also only at whatever the R1811 board can do, so 75% brightness?

I’ll have to try a few things and double check with my wife’s new Studio Display.

 

[SubDriver]

Sure @PaulD-UK. I will definitely report back.

@traxap Hoping you may be able to address one additional question about the SA1 performance. Specifically, I believe the two USB-A ports are USB 3.0 speed (see my post #2050). If this is accurate, it adds some potential useful functionality, such as leaving the hard drive (or a new SSD) installed and using a SATA to USB converter to connect the drive to the SA1.

Are you able to determine if the USB ports are USB 3.0? Maybe the USB-A port information shows up in System Information if a USB cable is used to connect the board and the computer?

 

[traxap]

@traxap Let us know here how it performs with 12 volts, as other people are asking about boards that perform well with 12v.

The SA1 board does not work well with the original iMac power supply. I suspect not enough power. It will turn on and the display works at 5K res., however, there is a high pitch noise cumming from the power board that I suspect is related to the 24v that the SA1 board requires, which the iMac power supply cannot deliver. Too bad!!! - I also tried an USB 3 4 port hub and the OS immediately disabled it due to "not enough power."

 

[yurazazik]

Привет ребята, а если просто подать питание на подсветку матрицы lm270qq1 без управляющего сигнала eDP, она загорится?

 

[PaulD-UK]

I should think so. The screen will remain dark but you should be able to see that the screen LEDs are alight. Worth a try.
Do you have an adjustable constant current LED driver?

 

[yurazazik]

I should think so. The screen will remain dark but you should be able to see that the screen LEDs are alight. Worth a try.
Do you have an adjustable constant current LED driver?

Do you mean the board that is purchased separately to increase contrast?

 

[PaulD-UK]

No. That needs to be controlled by a board.
I mean an LED driver PSU that controls the current so you won’t supply too much power to the LEDs and damage them.
The voltage for the backlight is described 12v, but it probably needs a higher voltage. The current has to be limited as that is how the brightness is controlled.

 

[yurazazik]

No. That needs to be controlled by a board.
I mean an LED driver PSU that controls the current so you won’t supply too much power to the LEDs and damage them.
The voltage for the backlight is described 12v, but it probably needs a higher voltage. The current has to be limited as that is how the brightness is controlled.

What if i connect only the backlight cable to the iMac and press the power button?

 

[SubDriver]

The SA1 board does not work well with the original iMac power supply. I suspect not enough power. It will turn on and the display works at 5K res., however, there is a high pitch noise cumming from the power board that I suspect is related to the 24v that the SA1 board requires, which the iMac power supply cannot deliver. Too bad!!! - I also tried an USB 3 4 port hub and the OS immediately disabled it due to "not enough power."

That’s too bad. Was really hoping it would work.

It is unlikely the iMac PSU isn’t powerful enough - pretty certain yours is 300W. Just not the right voltage.

I think that leaves you with 2 options… 1. Buying a 24Vdc power supply (either a laptop style power brick or a more formal internal power supply like the LRS-200-24).
2. Getting a 12Vdc to 24Vdc step up converter (probably need one rated for 10A/240W) and using the existing power supply. I am not certain if this method has been tried by anyone in this thread previously, but it should work since the output is exactly what the board needs.

If there is another option than the above I am very interested to learn about it.

Hope your luck turns around with the next attempt!

 

[PaulD-UK]

@yurazazik I did a google search, and it seems the screen panel backlight works at 30-40v.
At about 1.3 amps, and any more current will probably overload the LEDs.

So to test it you need to apply a high enough voltage (between 12 to 30v?) to get up to 1 amp (not more) through the LEDs.
There are many circuits to the screen backlight, all the Red+/Black– wires in the backlight cable need to be powered.

So a bit difficult to test....

 

[yurazazik]

I connected the backlight of the panel to the iMac with just one cable, but it still doesn’t light up. This means either there’s an issue with the panel itself, or the eDP cable also needs to be connected to activate it.

 

[PaulD-UK]

I can't see any electrical connection between the eDP T-Con board at the top of the screen, and the backlight power circuit at the bottom corners, so I don't think there is any activation process in the screen itself.
All that is controlled by the logic board in an iMac.

Did the screen backlight work OK in the iMac before the conversion was done?

 

[yurazazik]

I can't see any electrical connection between the eDP T-Con board at the top of the screen, and the backlight power circuit at the bottom corners, so I don't think there is any activation process in the screen itself.
All that is controlled by the logic board in an iMac.

Did the screen backlight work OK in the iMac before the conversion was done?

Yes, the screen worked fine, but I never tested the backlight separately.

Maybe the iMac’s board doesn’t supply power to the backlight when it doesn’t detect the eDP connection.

 

[traxap]

That’s too bad. Was really hoping it would work.

It is unlikely the iMac PSU isn’t powerful enough - pretty certain yours is 300W. Just not the right voltage.

I think that leaves you with 2 options… 1. Buying a 24Vdc power supply (either a laptop style power brick or a more formal internal power supply like the LRS-200-24).
2. Getting a 12Vdc to 24Vdc step up converter (probably need one rated for 10A/240W) and using the existing power supply. I am not certain if this method has been tried by anyone in this thread previously, but it should work since the output is exactly what the board needs.

If there is another option than the above I am very interested to learn about it.

Hope your luck turns around with the next attempt!

Yes, I suspected it will not work but it was worth trying.

A "12Vdc to 24Vdc step up converter" is a good suggestion. Thank you. I might try that.

I like the Mean Well LRS-200-24 8.8A, a larger foot print but a good option.

I have the laptop power brick which works well, however, Xarl-li's setup, post #1952, shows a less expensive option. He is using the AA1 board and opted for the 6A version, I opted for the 9A version.

This approach requires tapping/connecting into the iMac's power connector for a better look and fit inside the unit. You will need a female 3 pin Micro-Fit 3.0mm connector.

Again thank you for all your suggestions.

Female 3 pin Micro-Fit 3.0mm connector

 

[PaulD-UK]

@yurazazik “Maybe the iMac’s board doesn’t supply power to the backlight when it doesn’t detect the eDP connection.”

Yes, it won’t. One of the status LEDs on the bottom left of the logic board doesn’t light if there’s no handshake signal from the screen eDP connection.
It shuts down the logic board.

It's not clear whether the backlight is powered by DC voltage. Earlier iMacs used PWM, so a modulated pulse.

 

[SubDriver]

With @traxap's recent experience, I am leaning toward using an LRS-200-24 power supply connected to the original power socket as suggested by @PaulD-UK in post 882 and the discussions that follow on that page. He brings up some good points about grounding and EMI, both of which are important to ensure best results. Depending on how many of the original internal components I choose to keep, I might also get a 24Vdc to 12 Vdc (or 5Vdc) step down buck converter to provide them power.

My plan right now is to keep the iMac speakers and fans, keep the HDD installed, and add a SSD. The HDD and SSD would connect to a SATA to USB 3.1 Gen 2 controller.

I am simply waiting to decide between the R1811 board and the SA1 board since that will dictate how I connect to the drives. I think the SA1 USB-A ports are USB 3.0 (so 5 Gbps). That would allow me to connect the SATA to USB controller internally to the SA1 board and maintain only a single TB4 (USB-C) cable running from the host computer to the USB-C port on the SA1 board. If I use the R1811 board I would need to have a separate cable connecting the host computer to the SATA to USB converter to avoid the massive reduction in USB speed of the R1811 ports (USB 2.0, 480 Mbps).

I will probably make my decision in about a week (I am converting a 2011 iMac into a standalone display first).

Happy to hear any feedback on the above plan.

 

[PaulD-UK]

The R1811 has a connector to take a second switched 12v source of power, for the internal iMac fan, but I don't know whether it could power HDs etc.
It might be able to but whether is would be good for the R1811 I don't know...

There is the Noctua NA-VC1 24V DC to 12V DC step-down voltage converter but it is only 9 watt, so only enough for a fan.
How much power the SA1's USB-A ports can supply would also have to be tested.
These controller boards were designed for low price computer monitors so may not handle anything more than thumb drives...

Edit: "USB 3.0 can provide up to 900mA or 0.9A, which translates into 4.5 watts."

 

[SubDriver]

@PaulD-UK - Thanks. I understand your point about, These controller boards were designed for low price computer monitors so may not handle anything more than thumb drives... Edit: "USB 3.0 can provide up to 900mA or 0.9A, which translates into 4.5 watts."

I don't intend to power anything from the USB-A ports - just need them for the data connection, assuming they are also linked to the USB-C connector on the SA1 board.

I would power the HDD and SSD directly from the power supply via the step down converter I mentioned. It should work well assuming I can get the right connectors/adapters. That would minimize the stress on the SA1 or the R1811 board.

 

[PaulD-UK]

@SubDriver You need to check that the SA1 USB-A ports are connected to the USB-C port.
Normally a USB-B port is an input to a hub controller and the A ports are outputs.
But it would be strange if this is how it is wired.

The USB-B port is definitely a USB 3 type port.

 

[SubDriver]

@SubDriver You need to check that the SA1 USB-A ports are connected to the USB-C port.
Normally a USB-B port is an input to a hub controller and the A ports are outputs.
But it would be strange if this is how it is wired.

Yep... hoping @traxap or @PewQ or @kevinherring or someone else who has used the SA1 can confirm. I have tried asking StoneTaskin but I am having trouble explaining to them...

Even if it ends up that my idea doesn't work for the SA1 board, I would basically be in the same place I would be with the R1811 board since I have no desire to even try with its USB 2.0 ports.