Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Display brightness of my old iMac

@iMacConversionEnthusias
Looking at that picture, the blue socket is the audio out speaker connections.

The white JST PH 4 pin socket next to the remote control socket is a TTL peripheral socket - Transistor to Transistor Logic, to allow connection of some sort of control or diagnostic circuit.

The pinout is shown in this photo of the back of the board - I think it's the board you are using?
Note that the 3 sets of pins the middle of the board marked 12V/10V/5V are (almost certainly) NOT connection points, one (only) is jumpered to set the backlight voltage - 12v in the case of iMac screen panels.
So taking power from this point is not advisable!!!!!

One further point. The USB 5v and maybe the TTL 3.3v socket are probably powered all the time the PSU is connected to the board, and won't switch off when the board is in standby

iMac2011boardRear .jpg
 
Last edited:
  • Like
Reactions: iMacConversionEnthusias and csdesign3
SubDriver said:
Nice job with the ports! I may try something similar with mine in the future, but not right now.

Regarding the power supply, if you have access to an original PSU, I highly recommend you give it a shot. Although it is large and takes up a lot of space, it provides a significant amount of flexibility due to having numerous 12V power lines.

My final layout is shown in the images below. I haven't yet connected the audio to the crossovers (waiting on my small amplifier to arrive). Also, I haven't converted the SD card reader yet. I will complete both of those within the next couple of weeks.

The pictures below show the following:
1. Overall layout with everything installed in the iMac shell
2. Picture of the power button
3. Picture of the brightness control buttons
4. Picture of the brightness control button wires soldered to the PWM signal generator board (not great soldering, but it works!). :)
5. Short video showing the brightness control buttons changing the duty cycle of the PWM signal

View attachment 2476644
View attachment 2476645
View attachment 2476646
View attachment 2476647


View attachment 2476648
Click to expand...
Hi. Please share how is the sound with the crossovers. Is it much better? Are you using an amplifier?
 
iMacConversionEnthusias said:
Hi. Please share how is the sound with the crossovers. Is it much better? Are you using an amplifier?
Click to expand...
I haven’t hooked them up yet. Waiting for my other buck converter to arrive before re-opening the display - hopefully this weekend.

I will be using a small amplifier (5W). Lots of options out there to choose from. Given your use case for the display as you described several posts back, I would probably go with an 8-10W amp. My planned use of the display (wife’s work setup) doesn’t require much in the way of quality sound.
 
  • Like
Reactions: iMacConversionEnthusias
PaulD-UK said:
@iMacConversionEnthusias
Looking at that picture, the blue socket is the audio out speaker connections.

The white JST PH 4 pin socket next to the remote control socket is a TTL peripheral socket - Transistor to Transistor Logic, to allow connection of some sort of control or diagnostic circuit.

The pinout is shown in this photo of the back of the board - I think it's the board you are using?
Note that the 3 sets of pins the middle of the board marked 12V/10V/5V are (almost certainly) NOT connection points, one (only) is jumped to set the backlight voltage - 12v in the case of iMac screen panels.
So taking power from this point is not advisable!!!!!

One further point. The USB 5v and maybe the TTL 3.3v socket are probably powered all the time the PSU is connected to the board, and won't switch off when the board is in standby

View attachment 2481307
Click to expand...
Thank you. Very useful.
 
@iMacConversionEnthusias
Although your board has the circuit for an IR remote receiver decoder built in, it almost certainly doesn't have firmware to use this feature.

This is like most of the cheaper conversion boards, including the cheaper 5K boards.
The firmware has to be written using the software developer kit provided by the chipset manufacturer to write firmware that is suitable for the specific screen panel connected to the board.

Since these boards were originally developed for Chinese TV or monitor manufacturers, they could write their own OSD, and include firmware for an IR remote if they required.

The boards sold for iMac conversions are very low-cost items, and the necessary firmware to support an IR remote has only been written by one manufacturer, who makes better quality products - the CY.R9513 v5 4K board and the R9A18 and R1811 5K boards. The IR receiver is mounted on the control strip.

One builder using a cheap 5K JRY board has confirmed that the IR circuit on that board doesn't work.
 
Last edited:
PaulD-UK said:
@iMacConversionEnthusias
Although your board has the circuit for an IR remote receiver built in, it doesn't have firmware to use this feature.

This is like most of the cheaper conversion boards, including the cheaper 5K boards.
The firmware has to be written using the software developer kit provided by the chipset manufacturer to write firmware that is suitable for the specific screen panel connected to the board.

Since these boards were originally developed for Chinese TV or monitor manufacturers, they could write their own OSD, and include a IR remote if they required.

The boards sold for iMac conversions are low-cost items, and the necessary firmware to support IR remotes has only been written by one manufacturer - the CY.9513 v5 4K board and the R9A18 and R1811 5K boards.
Click to expand...
I understand. It is unfortunate there is no better versions, understandable to be more expensive, for the 2011 screen model. At least I have not found one. Thanks.
 
People have used joysticks, and other tactile switches, and everything is fine.
No reason a membrane switch shouldn't work just as well.

EDIT:
If that is an LED between the buttons, then another Arduino keypad on sale with an LED WILL NOT WORK.
The Arduino seems to use a common positive rail, with a common anode LED.

The R1811/R9A18 uses a common negative rail, with a common cathode LED, and your board seems to be marked Negative Ground, which is the same.

So for a keypad with no LED it doesn't matter which way you connect it, but if there is an LED it will not work the wrong way, and might damage the LED, or worse, the board.

So that keypad will work, but leave the LED unconnected.
 
Last edited:
PaulD-UK said:
People have used joysticks, and other tactile switches, and everything is fine.
No reason a membrane switch shouldn't work just as well.
Click to expand...
Hmmm, ok. I tried it yesterday, but it didn't work. I have to say the connection to the power button was wobbly. I managed to mess it up when I was soldering the wires to the keypad interface as it is so fragile, and I was impatient. So could the power button not being properly connected be the reason it did not work.
 
I have seen on more than one post that the PWM generator must be setup to 13.3 kHz, but when I ask ChatGPT or MS Copilot about the PWM on iMac A1312 the answer is 3 kHz. What frequency do you guys use, 13.3 or 3 kHz or something else?

EDIT:
I checked again on both ChatGPT and MS Copilot and now ChatGPT is saying 13.3 kHz and Copilot 13 kHz, but both are saying it is based on forums.macrumors.com :)
 
Last edited:
So, I am using the converted A1312 for a full day for first time. The temperature inside the box did not go higher than 45C. The box feels hot, but measured temperature did not go higher than 35C, but temp on the external PSU went up to 50C, 47.7C at the moment. I am using 2 40/40 permanent speed fans inside the box, one blowing at the inverter and one at the Chinese board. This decreased the temperature by 10% compared to when I was testing without the fans for about 3 hours. Three questions:

1. The colours look yellowish. Any idea what could be the reason for it?
2. The brightness I use is between 75 and 80 % measured by the duty setting on the PWM because above 80 the screen starts to flicker rapidly, and it doesn't stop until the duty is reduced. Any idea what could be causing it?
3. Has anybody measured the temperature inside the box and more importantly around the inverter?

Thanks.
 
Last edited:
PaulD-UK said:
People have used joysticks, and other tactile switches, and everything is fine.
No reason a membrane switch shouldn't work just as well.

EDIT:
If that is an LED between the buttons, then another Arduino keypad on sale with an LED WILL NOT WORK.
The Arduino seems to use a common positive rail, with a common anode LED.

The R1811/R9A18 uses a common negative rail, with a common cathode LED, and your board seems to be marked Negative Ground, which is the same.

So for a keypad with no LED it doesn't matter which way you connect it, but if there is an LED it will not work the wrong way, and might damage the LED, or worse, the board.

So that keypad will work, but leave the LED unconnected.
Click to expand...
Aha, thanks. Yes, it is an LED. I will definitely try it, unfortunately it can only happen next week. The LED lit up when I tried it, but nothing else worked on the keypad.
 
First of all I want to thank all the contributors of the project! Your work and information sharing is amazing!
I use the original PSU and I intend to use the apple inverter when the necessary items arrive.
I have a question: Do you think it's better to connect all 3 12v lines to one and then give power to all the boards or to power every board with different line? Same question with the Ground lines?
Furthermore, when I am on windows foldes the brightness is perfect and low brightness happens when I play videos or seeing pictures. Did you had the same problem?
 
Last edited:
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back