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.