- Joined
- May 12, 2020
- Messages
- 7
- Motherboard
- I like to hack old tech, which often means removing the motherboard
- CPU
- mostly Apple computers
- Graphics
- the latest and greatest
- Mac
- Mobile Phone
A friend has asked if I can turn his 20" iMac G5 iSight (A1145) into an external monitor that he can use with his Apple laptop via HDMI (sorry, don't know the laptop model, but luckily that's not particularly relevant to this project). Most of the info out there about projects like this one tends to focus either on G4 mods, or G5 17" mods, or non-iSight computers, and the interface of choice appears to be a DVI connector, not HDMI. But because DVI and HDMI are both compatible with the TMDS monitor format, I've decided to attempt the latter (HDMI). Judging from my work on the project to date, I give this a 50/50 shot at success. It's worth mentioning that doing this mod on the 20" iSight iMac is substantially different than on previous G5 generations.
For those who are primarily interested in the destination rather than the journey, and who really just want to get your iMac up and running as an external monitor with the least amount of hassle, I recommend ordering an LCD driver controller kit for $50 off ebay. This is effectively a plug and play solution, though if you want it all to look good you'll still have to gut most of the components from the computer, which will take you about an hour (just make sure you've got the right size Torx bits before you begin). You'll also need an external 12V/4A power supply with a barrel jack to power the driver board, though if you're feeling adventurous you could probably just tap into the 12V power coming off the Apple PSU and put a cool vintage switch in line for easy on/off functionality. When you buy the driver board, be sure you're ordering for the right monitor: LM201W01-STB2. This kit is a much, much easier solution than what I'm attempting.
For those of you who are still with me, I'll now outline where the project is at the moment and what the main challenges are. I've removed all the components from inside the computer except for the power supply, the inverter board, and the long snake of cables that connects the inverter board to the logic board. The fans, speakers, logic board, hard drive, and optical drive are all sitting in a pretty pile next to my workbench, likely destined for the e-waste bin (though I might reinstall a fan and the speakers if the project is successful).
The two main challenges for this project are 1) powering the monitor, and 2) retro-fitting the monitor cable to a female HDMI connector.
1) Powering the monitor
This process is not intuitive, and the only reason I know about it is from a few brave souls on the internet who have somehow figured out how to do this, most notably user ersterhernd's post on this forum. On this model of iMac the power supply feeds into an inverter board, which in turn feeds the main logic board with a long snake of cables that terminate in a 14-pin connector. Power for the LCD backlight comes from four cable clusters coming off the inverter board. The data for the LCD (and a bit of power driving the image on the LCD) comes from the logic board. We are going to continue to use the inverter board to power the LCD backlight through some trickery that allows us to disregard the logic board entirely. If we look at the back side of the logic board (which we have removed and discarded) you can see some of the pinout information for the cables coming from the inverter. They are printed on the board next to the female socket. I've cobbled this more complete pinout diagram:
These pin numbers are arbitrary (the connector isn't labelled, so I assigned my own numbers). All of the power pins marked "ALL" are hot whenever the computer is plugged into mains power. The RUN power pins are floating: they can be activated by tying Pin 13 low (to GND), and deactivated by tying pin 13 high (to 3V3_ALL). Tying LCD_PWM high (to 3.3V) activates the LCD backlight. I'm not yet sure what the function is for POWER_GOOD and INV_CPU_HI, or whether they are relevant to our specific mission. The YouTube user "3beltwesty" has a wonderful series of short videos demonstrating some of this.
I suspect that this process of activating and deactivating the RUN voltages is how the user will power the monitor on/off. I just need to figure out how to put in a switch in a way that is user friendly. I welcome any and all advice regarding this question.
2) Retrofitting the LCD cable for HDMI
This part of the project definitely feels like I'm out on the frontier, as I haven't been able to find nearly as much information as I would like about the LCD monitor cable pinout. In short, there is a 30-pin connector that goes from the back of the monitor to the logic board, terminating in what appears to be one Apple's obscure proprietary connectors. Our objective is to hack the logic board end of the cable and affix a female HDMI connector, which we will then mount so that it protrudes through the back of the computer case. Ersterhernds has provided a very thorough chart with a pinout from this monitor going to DVI, but there are inconsistencies between that chart and the 30-pin connector on my machine (many of the wires are a different color, and somehow there is an extra wire coming from my connector that isn't accounted for in the chart.
After peeling back some of the outer layers on the other connector (where the female HDMI hub will go), I was able to shine some light on this mystery, but new inconsistencies arose:
The labeling on this connector answers questions about some of the mystery wires, all of which are grouped together either as GND or 3.3V. But 3.3V seems strange, firstly because of the size of the monitor, and even more so because the chart from user ersterhernd lists these pins as 12V. So clearly there's some information I'm missing. Would love to hear thoughts/ideas on this from the forum.
I borrowed ersterhernd's beautiful chart format, plugging in my own values for what I *think* is a correct pinout for HDMI:
UPDATED to include data from the following post
I'm going to stop here for now. Hoping some of you can chime in on the pinout chart that I've made, and that perhaps this helps a few people down the road who are attempting a similar mod.
For those who are primarily interested in the destination rather than the journey, and who really just want to get your iMac up and running as an external monitor with the least amount of hassle, I recommend ordering an LCD driver controller kit for $50 off ebay. This is effectively a plug and play solution, though if you want it all to look good you'll still have to gut most of the components from the computer, which will take you about an hour (just make sure you've got the right size Torx bits before you begin). You'll also need an external 12V/4A power supply with a barrel jack to power the driver board, though if you're feeling adventurous you could probably just tap into the 12V power coming off the Apple PSU and put a cool vintage switch in line for easy on/off functionality. When you buy the driver board, be sure you're ordering for the right monitor: LM201W01-STB2. This kit is a much, much easier solution than what I'm attempting.
For those of you who are still with me, I'll now outline where the project is at the moment and what the main challenges are. I've removed all the components from inside the computer except for the power supply, the inverter board, and the long snake of cables that connects the inverter board to the logic board. The fans, speakers, logic board, hard drive, and optical drive are all sitting in a pretty pile next to my workbench, likely destined for the e-waste bin (though I might reinstall a fan and the speakers if the project is successful).
The two main challenges for this project are 1) powering the monitor, and 2) retro-fitting the monitor cable to a female HDMI connector.
1) Powering the monitor
This process is not intuitive, and the only reason I know about it is from a few brave souls on the internet who have somehow figured out how to do this, most notably user ersterhernd's post on this forum. On this model of iMac the power supply feeds into an inverter board, which in turn feeds the main logic board with a long snake of cables that terminate in a 14-pin connector. Power for the LCD backlight comes from four cable clusters coming off the inverter board. The data for the LCD (and a bit of power driving the image on the LCD) comes from the logic board. We are going to continue to use the inverter board to power the LCD backlight through some trickery that allows us to disregard the logic board entirely. If we look at the back side of the logic board (which we have removed and discarded) you can see some of the pinout information for the cables coming from the inverter. They are printed on the board next to the female socket. I've cobbled this more complete pinout diagram:
These pin numbers are arbitrary (the connector isn't labelled, so I assigned my own numbers). All of the power pins marked "ALL" are hot whenever the computer is plugged into mains power. The RUN power pins are floating: they can be activated by tying Pin 13 low (to GND), and deactivated by tying pin 13 high (to 3V3_ALL). Tying LCD_PWM high (to 3.3V) activates the LCD backlight. I'm not yet sure what the function is for POWER_GOOD and INV_CPU_HI, or whether they are relevant to our specific mission. The YouTube user "3beltwesty" has a wonderful series of short videos demonstrating some of this.
I suspect that this process of activating and deactivating the RUN voltages is how the user will power the monitor on/off. I just need to figure out how to put in a switch in a way that is user friendly. I welcome any and all advice regarding this question.
2) Retrofitting the LCD cable for HDMI
This part of the project definitely feels like I'm out on the frontier, as I haven't been able to find nearly as much information as I would like about the LCD monitor cable pinout. In short, there is a 30-pin connector that goes from the back of the monitor to the logic board, terminating in what appears to be one Apple's obscure proprietary connectors. Our objective is to hack the logic board end of the cable and affix a female HDMI connector, which we will then mount so that it protrudes through the back of the computer case. Ersterhernds has provided a very thorough chart with a pinout from this monitor going to DVI, but there are inconsistencies between that chart and the 30-pin connector on my machine (many of the wires are a different color, and somehow there is an extra wire coming from my connector that isn't accounted for in the chart.
After peeling back some of the outer layers on the other connector (where the female HDMI hub will go), I was able to shine some light on this mystery, but new inconsistencies arose:
The labeling on this connector answers questions about some of the mystery wires, all of which are grouped together either as GND or 3.3V. But 3.3V seems strange, firstly because of the size of the monitor, and even more so because the chart from user ersterhernd lists these pins as 12V. So clearly there's some information I'm missing. Would love to hear thoughts/ideas on this from the forum.
I borrowed ersterhernd's beautiful chart format, plugging in my own values for what I *think* is a correct pinout for HDMI:
UPDATED to include data from the following post
I'm going to stop here for now. Hoping some of you can chime in on the pinout chart that I've made, and that perhaps this helps a few people down the road who are attempting a similar mod.
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