Display brightness of my old iMac

[Balsie]

That's correct, that's how I have it connected. What is the issue?
Thanks!

You should feed the Chinese board from the original PSU with + (pin 11,12 or 13) and GND (pin 1,3,5 or 9).
PS_ON (pin 6) must be connected with GND (pin 7) to turn on the PSU.
You can use a switch (no moment, like the original Mac on/off switch), but a permanent one to switch the PSU on/off.
My configuration is perfectly working, are you interested?

 

[SubDriver]

You should feed the Chinese board from the original PSU with + (pin 11,12 or 13) and GND (pin 1,3,5 or 9).
PS_ON (pin 6) must be connected with GND (pin 7) to turn on the PSU.
You can use a switch (no moment, like the original Mac on/off switch), but a permanent one to switch the PSU on/off.
My configuration is perfectly working, are you interested?

Agree with @Balsie and it is a good catch to notice that detail in your diagram. I assumed that was a typo or something since you stated you had followed my guide. Pin 6 is not a pin to supply power.

Anytime the power supply is plugged into an AC outlet, you will have power at Pin 4 and Pin 6. Neither of those are ideal to power the LCD driver board, especially Pin 6. As stated, you short Pin 6 to Pin 7 to turn on the rest of the power supply Pins and then use Pins 11, 12, or 13 to provide the 12Vdc to the LCD driver board.

I elected to use the 12Vdc lines from the driver board to connect to the step down voltage converter and the buck voltage regulator for my final build.

 

[Monja96]

I followed your advice and I finally got an image! Having the board connected with the PSU ON was a big mistake.

Right now, the screen seems a bit dim and, most notably, it's flickering a lot. What could be the cause?

 

[SubDriver]

I followed your advice and I finally got an image! Having the board connected with the PSU ON was a big mistake.

Right now, the screen seems a bit dim and, most notably, it's flickering a lot. What could be the cause?

View attachment 2503762

Please provide us with details of all the electrical connections. A new diagram would be useful.

Possibilities:
1. Loose connection between the LCD driver board and the screen
2. Loose connection to the inverter (either the PWM or the BLO/ENA)
3. Incorrect PWM setting
4. Poor quality BLO signal (essentially the BLO signal is turning on and off rapidly)
5. Something unknown

 

[Balsie]

I followed your advice and I finally got an image! Having the board connected with the PSU ON was a big mistake.

Right now, the screen seems a bit dim and, most notably, it's flickering a lot. What could be the cause?

View attachment 2503762

Sorry to hear that.
What is your duty cycle setting on your PWM?
Too high or too low may cause flickering, if you set it to 70 it should work.
The worst case scenario is, that your Chinese board is damaged.
You can test it with your Chinese inverter (if you still have it).
If that works you know the basic is working.
Let us know and good luck.

 

[Richy85]

iMac 2009

 

[imacker2011]

Today, I also tried to connect my chinese driver board directly to the Apple inverter. As expected, it did not work. I also only got a black screen. I measured the voltages: BL_ON was about 5V, PWM around 0,3V (if I remember it correctly). The model of my inverter is V267-602HF.

Are there actually any known instances of the V267-601HF model failing to work directly with the Chinese boards? Otherwise I would consider getting one of these in used condition. I would really like to keep the possibility to control the brightness with MonitorControl while gaining full brightness.

 

[SubDriver]

Today, I also tried to connect my chinese driver board directly to the Apple inverter. As expected, it did not work. I also only got a black screen. I measured the voltages: BL_ON was about 5V, PWM around 0,3V (if I remember it correctly). The model of my inverter is V267-602HF.

Are there actually any known instances of the V267-601HF model failing to work directly with the Chinese boards? Otherwise I would consider getting one of these in used condition. I would really like to keep the possibility to control the brightness with MonitorControl while gaining full brightness.

Unfortunately, there isn't much information about using the original inverters that I have found, especially connected directly to the Chinese board - this thread could be the most comprehensive on the web 🤷‍♂️.

Everything I see for all the A1312 inverters indicates they need 3.3Vdc for the enable and PWM signals and the PWM frequency is 13.3kHz regardless if they are the 2009, 2010, or 2011 variant of the A1312. I am not certain what could have possibly allowed those VERY FEW who reported success connecting the inverter directly to the Chinese board unless their board was delivering enable and PWM signals close to the 3.3Vdc and 13.3kHz I mentioned above.

I would recommend the following:
1. Buy a step down converter and a PWM generator to produce the 3.3Vdc and 13.3kHz needed by the inverter (total of ~$22 US)
2. Connect a wire from 12Vdc on your Chinese board to the input of the step down converter (reduces the 12Vdc to 3.3Vdc)
3. Connect the 3.3Vdc output of the step converter to two places:

a. The enable pin on the inverter​

b. The input of the PWM board​

4. Connect the output of the PWM board to the PWM pin on the inverter

This should NOT prevent you from using the Monitor Control app to manage your screen brightness - I can use either my brightness control buttons or the Monitor Control app for my display - both methods work. For my build, I elected to go further and connect brightness control buttons directly to the PWM board as I wanted more control over the brightness than was possible with the Monitor Control app.

 

[imacker2011]

Hey guys,

great success to report here: After my last post, I bought a used 2009 Apple inverter (V267-601HF). Just connected it directly to the China board (without PWM board and step-down converter) and guess what: It works. Brightness now keeps up with my iMac 2011. However, some issues remain:

- Brightness slider is reversed (mentioned earlier in this thread; at the moment I am using Software Dimming in Monitor Control to dim brightness, DDC and OSD are working in the wrong direction)

- Screen flickering if brightness is more than app. 75%. This is most probably due to the power supply. I am using the original PSU, however, at the moment through the standby pins without intermediate (latching) power button.

Has anyone managed to do something about the slider? And secondly, @SubDriver: In a previous post, you said that it is not ideal to use the standby pins from the PSU to feed the Chinese board. Would there be actually any problems with permanently powering the PSU (by connecting PS_ON with GND) without using a switch?

EDIT: Ok, regarding the inverted brightness slider, I just realized that MonitorControl offers an option to reverse DDC controls.

 

[SubDriver]

Hey guys,

great success to report here: After my last post, I bought a used 2009 Apple inverter (V267-601HF). Just connected it directly to the China board (without PWM board and step-down converter) and guess what: It works. Brightness now keeps up with my iMac 2011. However, some issues remain:

- Brightness slider is reversed (mentioned earlier in this thread; at the moment I am using Software Dimming in Monitor Control to dim brightness, DDC and OSD are working in the wrong direction)

- Screen flickering if brightness is more than app. 75%. This is most probably due to the power supply. I am using the original PSU, however, at the moment through the standby pins without intermediate (latching) power button.

Has anyone managed to do something about the slider? And secondly, @SubDriver: In a previous post, you said that it is not ideal to use the standby pins from the PSU to feed the Chinese board. Would there be actually any problems with permanently powering the PSU (by connecting PS_ON with GND) without using a switch?

EDIT: Ok, regarding the inverted brightness slider, I just realized that MonitorControl offers an option to reverse DDC controls.

As long as u jumper the PS_ON to GND with a good quality connection, I would not expect any problems.

You could plug in the power cord into an outlet, power strip, or surge protector controlled by a switch. This could be used to turn the monitor on/off instead of a power button on the case. I would highly recommend one of these methods to ensure you don’t prematurely burn out your power supply or monitor

Here are a couple of examples:
Remote control outlet switch
Switch with cord

Good to hear you are having success with the 2009 inverter. To help others out, it would be great if you could post the exact voltage being fed to the ENA (or BL_ON) inverter pin, the voltage to the PWM pin, and the frequency going to the PWM pin.

 

[imacker2011]

I just switched the power supply lines to pin 1 and 11 (with pin 6 and 7 permanently connected) on the original Apple PSU. The flickering isn't completely gone, but I have the impression that the brightness is now even higher than the iMac 2011 display when fully maxed out. Hence, I used the advanced settings in the Monitor control app to limit DDC min (!) (because of the inverted slider) to value 50. This way, the two screens have the same brightness level without flickering. I have a wifi switch with an integrated ammeter connected to the power line of the monitor. Since in "power save" mode the system draws 0,0W I will most probably just leave it like that.

A great advantage of using DDC controls is that when the brightness is dimmed, also power consumption decreases. It now ranges from app. 55W when lowest to app. 90W when maxed out.

As requested, I measured the voltages coming from the China board now at the black plug:

BL_ON: 0,03V
+: 12,08V
PWM: 5,03V

Unfortunately, I only have a simple multimeter and could thus not measure the frequency going to the PWM pin.

Now, however, comes a big surprise. When I had the screen opened, I connected the Apple 2010 inverter (V267-602HF) again. And, very strangely, it now also worked. The OSD message (No Cable) instantly popped up with full brightness. I can only explain this by the now properly soldered cables between the China board and the Apple inverter. When I tested this out in the first place, I had the connection done only with some small pins in the plug, which maybe did not have proper contact. I did not want to cut the China connection cable before I knew it would surely work.

 

[SubDriver]

I just switched the power supply lines to pin 1 and 11 (with pin 6 and 7 permanently connected) on the original Apple PSU. The flickering isn't completely gone, but I have the impression that the brightness is now even higher than the iMac 2011 display when fully maxed out. Hence, I used the advanced settings in the Monitor control app to limit DDC min (!) (because of the inverted slider) to value 50. This way, the two screens have the same brightness level without flickering. I have a wifi switch with an integrated ammeter connected to the power line of the monitor. Since in "power save" mode the system draws 0,0W I will most probably just leave it like that.

A great advantage of using DDC controls is that when the brightness is dimmed, also power consumption decreases. It now ranges from app. 55W when lowest to app. 90W when maxed out.

As requested, I measured the voltages coming from the China board now at the black plug:

BL_ON: 0,03V
+: 12,08V
PWM: 5,03V

Unfortunately, I only have a simple multimeter and could thus not measure the frequency going to the PWM pin.

Now, however, comes a big surprise. When I had the screen opened, I connected the Apple 2010 inverter (V267-602HF) again. And, very strangely, it now also worked. The OSD message (No Cable) instantly popped up with full brightness. I can only explain this by the now properly soldered cables between the China board and the Apple inverter. When I tested this out in the first place, I had the connection done only with some small pins in the plug, which maybe did not have proper contact. I did not want to cut the China connection cable before I knew it would surely work.View attachment 2521432

Congratulations on your success! I wish there was something definitive that could be determined about why some have success using the original iMac inverter straight from the driver board without any other modifications while others don't.

Regarding your BL_ON reading, that is a very low voltage for proper functionality of the backlight. Any chance this is a typo? Or maybe you didn't have a good connection on your multimeter? Or maybe you accidentally read one of the GND pins on the inverter instead of the BL_ON?

 

[imacker2011]

Congratulations on your success! I wish there was something definitive that could be determined about why some have success using the original iMac inverter straight from the driver board without any other modifications while others don't.

Regarding your BL_ON reading, that is a very low voltage for proper functionality of the backlight. Any chance this is a typo? Or maybe you didn't have a good connection on your multimeter? Or maybe you accidentally read one of the GND pins on the inverter instead of the BL_ON?

Thank you, I am actually quite happy about the increased brightness. It is a great improvement for daily work!

I agree that the voltage readings are strange. I am definitely not an expert in conducting these measurements (cf. my cheap multimeter) but I double checked if I had the right pins and I definitely had no typo in writing down the values. I also remember the first time trying to connect to the 2010 inverter, I also had somehow strange values.

The only (small) downside I face right now is that there is a (rather light) high-pitched noise, which most probably stems from the vsync cable not being connected to the Apple inverter. I tried to connect it, but unfortunately the plug from the 2010 screen is not compatible with the 2009 inverter I have just acquired. And the 2010 inverter, which was originally connected to the SDC2-panel, was damaged by the previous owner at this very vsync connector.