imac G4 DVI MOD need help with LCD backlight

[Vincentlaw]

Hi guys,

I'm in the process of modding my imac g4 and I'm facing a problem for more than two weeks. Bought a second G4 because of this unfortunately with the same problem. The LCD screen flashes for a second when testing the backlight and that's it. I have already tried everything. With aligator clips without aligator clips. The grounding coupled with the cage. Everything did not work. I use the power supply that Dremeljunkie recommends in his tutorial. DC to Molex supply. Is it possible that the power supply has too little or too much watt ? My power supply has 60 watts. I am really desperate because until now everyone said that it is the GND. If someone has another method I would be really grateful. Thank you for any help.

Best
Vincent

PS : This is my connection from the inverter to the power supply:

Blue - > 12 Volt
Black - > Ground + Aligator Clips to Cage
Red - > 5V
Green - > 1k Ohm - > 5V
Orange floating
Purple floating

 

[howdood]

Hi - I had this exact problem this week. I think the solution is definitely ensuring a strong earth connection for the black wire in the inverter cable. Mine was behaving as above when earthed via a breadboard and small gauge wire, but it works fine on slightly thicker wire connected via screw terminals. I think there must be a minimum thickness of ground wire below which the inverter shuts itself down. Maybe it senses a different capacitance in the thinner wire or something? Anyway, try making sure your earth wire is thicker than the wire coming back from the inverter, and securely connected at both ends. (NB you don't need to earth it via mains plug earth - a secure connection to the DC -ve of the PSU should be enough).

Hope that helps!
h

 

[Syan]

I'm having the same issue. I am trying to mod an iMac G4 15", 1GHz, USB 2.0 model. I'm using the original PSU and Dremeljunkie pinouts. When connecting the red inverter cable to 5V the backlight flashes for 1/2s then turns off. I've opened the display and tested every cable, all seem to be fine. When plugging only one backlight to the inverter it stays ON a bit longer, which makes me think of a current issue.

Here are some pictures of the ongoing mod. I kept the converter red wire hanging to later attach to the corresponding HDMI pin. In the mean time i manually put it on the exposed 5V line to test the backlight. I have tried soldering it to see if the flickering disappears, it did not. I also tried connecting one of the molex grounds to the cage but it didn't change a thing either.

Could this be related to this : https://www.tonymacx86.com/threads/imac-g4-globe-15-pinout-help-no-video.160544/#post-1011895 ? It also seems 3.3V to the green wire would be better than 5V, maybe I should replace the DC converter with a PicoPSU to get a 3.3V line and maybe more stable 12V and 5V lines.

 

[AstroDeNaCl]

Hello, first of all, forgive me for my English, I am trying to do the same with an iMac G5 A1076, (there is a lot of documentation in this same forum thanks to kiwisincebirth and ersterhernd) some authentic cracks.

The fact is that I'm stuck because I manage to turn on the illumination of the iMac screen, but nothing appears on the screen when I turn on the Nuc, only the illumination of the screen.
Let's see if we can all help each other
Greetings from Spain