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MacTester57's HemiMac G4

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Thanks for the praise. :)

As promised, here are the details about the brightness control.

Disclaimer:
I am not responsible, if you work with mains voltage. This is dangerous, if you don't know what you do! ;)


Important:
The faraday cage must always be properly grounded to the wall outlet! Otherwise the CCFL dimming does not work properly, because the reference voltage on the green neck wire is oscillating.


Wiring diagram:
iMac G4 Brightness Control.jpg


Actualized table:
iMac G4 LCD Wiring.jpg


and the corresponding test wiring:
iMac G4 CCFL Brightness Test Wiring.jpg


MacTester
 
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Very informative, MacTester, thank you so much for the solution layout. Maybe I'm jumping ahead of you here, but how does the OS interface with the setup, that is, the slider bar in display preferences? With the green wired directly as in my first iMac build, there is no slider at all, not even a greyed out one. Something must trigger the OS to read available hardware to perform brightness operations.

Great work.


Ersterhernd
 
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Very informative, MacTester, thank you so much for the solution layout. Maybe I'm jumping ahead of you here, but how does the OS interface with the setup, that is, the slider bar in display preferences? With the green wired directly as in my first iMac build, there is no slider at all, not even a greyed out one. Something must trigger the OS to read available hardware to perform brightness operations.

Great work.


Ersterhernd
Ersterhernd,

You' re welcome. I would recommend to do it, because the way as dremeljunkie wired the green neck wire could kill the inverter. I' ve measured the resulting voltage with a 1KOhm resistor @ 5V (about 4.7 V, which is too much).

I think there will be no way, that the dimming via keyboard shortcuts will work as long as the required USB interface is apple's secret.

At the moment, I see two possibilities:
1. The potentiometer, which could be mounted in the former modem socket or in the kensington lock hole.
2. A PWM signal from the PICAXE microcontroller

Today, I've wired the DVI adapter.

The wiring was done in accordance with dremeljunkie's blog (thanks again): http://www.dremeljunkie.com/2011/08/guide-step-by-step-17-imac-g4-tmds-to.html
Caution: The VCC wires for the LCD have to be connected to 3.3 V instead of 5 V, because the LCD-panel datasheet says that the max voltage is 3.45V!!

Soldering the three VCC 3.3V supply wires to an orange wire:
iMac G4 3.3V wiring.jpg


Soldering the three GND wires to a black wire and to the grey wire for DVI GND:
iMac G4 GND wiring.jpg


Spliced Hot Plug wire with a 1kOhm resistor. The thick red wire goes to the red inverter neck-wire:
iMac G4 Hot Plug wiring.jpg


The finished DVI adapter. The two thick outer black wires are connected to the cable shields:
iMac G4 wired DVI adapter.jpg


Succes!!! :) :
iMac G4 _first _sreen.jpg


MacTester

BTW:
I did not use wires from an additional neck!
 
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Looks great, Mactester.

Perhaps I should plug the green wire into a 3.3v slot in the picopsu. It's in a 5v with a 1k ohm resistor currently.

Your thoughts?


EDIT : I just rewired my first iMac build so the green wire (from inverter cable) goes to 3.3V on the PicoPSU via a 1.1k Ohm resistor. Did not test the voltage, but the screen works fine configured this way. It doesn't need the 5V. Actually as you said, it should NOT be on a 5V source. Brightness is same as was on the 5V connection.



Ersterhernd
 
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Hi MacTester!

Great work,

Would you please re-upload the 2 images missing:

-Wiring diagram:
-Actualized table:

thank you very much!
 
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Hi MacTester!

Great work,

Would you please re-upload the 2 images missing:

-Wiring diagram:
-Actualized table:

thank you very much!
Thanks for praise. The pics are OK, try to empty your browser cache.

I've made some additional tests with the modded screen unit. If it is connected to my oldest hack with Intel DP35DP MOBO & GF6800GT crapics card, the artifacts are gone. :) The GA-Z68MX-UD2H MOBO in my G5 hack with its integrated HD-3000 graphic was always difficult and produced lots of artifacts till now. :thumbdown:

The 2nd iMac G4, which I've auctioned last week showed up today. After a bit cleaning it's in perfect condition: :thumbup:
Oh my god, what a mess in here... :ugeek:
iMac G4 2nd unit.jpg


The PIXACE microcontroller, which I intend to use to reproduce the breathing sleep LED has also arrived:
iMac G4 Picaxe.jpg


MacTester
 
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Sorry, it's probably my connexion at work:banghead:

Thank you anyway!

ps: i'm trying to make the mod on the 20", and i'm doubting about the real need to use 3.3V instead of 5V (because on his guide, depending of the power supply, the yellow inverter cable does not need the same Voltage... Jberg doesn't reply so if you have an idea...


http://4.bp.blogspot.com/--f2oDQP28y8/TtcKEiHNl9I/AAAAAAAABFY/znznsRGSkD8/s400/Inverter+20%22.png

http://1.bp.blogspot.com/-0F6ksLRDrtk/TsSBHiR2mtI/AAAAAAAABDY/o5OS62ZJIpc/s320/Image.jpg

thank you very much!

the diming option would be ideal!!:mrgreen::mrgreen::mrgreen::mrgreen::mrgreen:

Franchois
 
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I'm sorry, but I know nothing about the 20" model. I've only heard, that its inverter works with 24V and is completely different.

Tonight, I've quickly soldered a PICAXE prototype board and programmed a "fake Apple sleep LED" :headbang:
iMac G4 fake sleep LED prototype.jpg


Here is a short video, where you can see how it works:


MacTester
 
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