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MacTester57's HemiMac G4

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Hi Guys

A while ago, I've read jberg44's (aka dremeljunkie) blog with its wiring diagrams (great, thanks): http://www.dremeljunkie.com

Recently, I've read Ersterhernd's NUCiMac thread an this activated the "must have reflex": http://www.tonymacx86.com/imac-mods/102250-ersterhernds-nucimac-g4.html

Here is my project: The HemiMac G4 :ugeek:

Why this name?
1. The iMac G4 has a "hemispherical" base
2. A "hackintoshed" classic Mac is like a Hotrod for me - classic body with modern innards - and they mostly have a big V8 engine with "Hemi" combustion chamber: http://en.wikipedia.org/wiki/Hemi_engine

So I bought the 1st iMac G4 17" / 1.25 GHz:
iMac G4 Ricardo.jpg



Unfortunately it is not in best condition: It was a scool computer and has some willful damage like a screen with scratches in every corner. I was disappointed and auctioned an 2nd identical unit, which hopefully will be in better condition:
iMac G4 Ricardo 2.jpg


Goals of this project:
-outside as original as possible
-optical drive
-original speakers, connected with the original 2.5mm plug
-internal PSU
-silent (the original iMac is loud)
-working LCD backlight dimming
-original "breathing" sleep LED (I intend to use a PICAXE microcontroller)
-USB 3.0

First works on the 1st unit:

The optical drive door did not close properly, so I've added M3 washers under the screw heads:
iMac G4 drive door fix.jpg


The "Fleckenradierer" is ideal for cleaning dirty iMac housings: (use a bit water)
iMac G4 Fleckenradierer.jpg


The back side after cleaning:
iMac G4 back view.jpg


A first look to the innards and cleaning:
iMac G4 original inside.jpg


This is a USB 2.0 model (iMac3.3) and the connectors are not the same shape as Ersterhernd's:
iMac G4 original back.jpg


As I said earlier, one of the goals is a working LCD CCFL dimming. To allow this, some investigations on the inverter connector were necessary:
iMac G4 LCD measuring 1.jpg


iMac G4 LCD measuring 2.jpg


As you can see, I discovered, that the "dimming" signal is on the green (neck) wire: 0.7V = Min. brightness / 3.14 V = Max. brightness! The orange wire has always 3.3 V and I assume, that it is for the 3.3 V supply of the inverter's microcontroller. We will see...
iMac G4 LCD Wiring.jpg


MacTester

Edit: some pictures of the modding process for comparison.
iMac G4 Hackintosh Gallery.jpg


Edit: video summary
Build video:

Video presentation:

After the macOS Sierra update:
 
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Wow! Those are aggressive goals, Mactester! Like your Cube, this project will certainly end up fabulous. I'm very interested in reading your take in the LCD dimming, as to what's involved in the wiring.

Good Luck!
 
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Cool Mactester!

this will be a tough job but I think it wil be worth it!

So far I can see on the pics the screen looks okay.

Men now I want an iMac g4 to:O

Have fun Mactester! This wil be great to follow!

Rick,
 
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Thanks, guys!

I know, that those goals are aggressive. After I've disassembled the base and did some measuring I have to say that it will be almost impossible to integrate a mini ITX board under the optical drive - it would fit, but there is only 15mm height available...
iMac G4 mini ITX.jpg


If I want USB 3.0 and an optical drive, I will have to wait for the Haswell NUC or will have to use the GIGABYTE BRIX GB-XM12-3227 (which only has 2 USB 3.0 ports)

MacTester
 
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Today, I've done several works:

1. Installing the new WiFi:
I've used this TYCO Laptop Wireless Mini PCI PCI-E Internal Antenna:
http://www.ebay.com/itm/TYCO-Laptop-Wireless-Mini-PCI-PCI-E-Internal-Antenna-/260668842387?ssPageName=ADME:L:OC:CH:3160
iMac G4 new WiFi antenna.jpg


To allow the antenna replacement, the faraday cage had to be removed:
iMac G4 Faraday Cage removed.jpg


This is the old antenna:
iMac G4 old WiFi.jpg


iMac G4 old WiFi 2.jpg


And the new one. An A1181 BT antenna was also installed:
iMac G4 new WiFi 2.jpg


iMac G4 new WiFi 1.jpg


2. The bad part of the story... :banghead:

The backlight does not work properly. I think the inverter died...

This is the test setup with a 22kOhm potentiometer for the brightness-regulation. As I said yesterday, the green neck-wire is for the dimming. It works, but not as it should - @ 0.6 V the CCFL begins to flicker - @ 0.64 V it stays on, but is dimmed (as it should at this voltage, see table) - If the voltage rises over 0.7 V, the CCFL shuts off and can only be activated, if the red On / Off wire is removed from the 5V supply and then reconnected. I've also tested the wiring according to dremeljunkies table - that does not work either... (the CCFL turns on for about 0.2s and then shuts off)
iMac G4 Backlight testing.jpg


I then disassembled the whole screen unit. The inverter looks OK
iMac G4 LCD removed.jpg


iMac G4 LCD Back.jpg


iMac G4 Inverter.jpg


...nothing changed after reassembling. Only dimmed light works. :banghead: Any thoughts?

MacTester
 
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Hi Mac Tester, great build look forward to your progress.

Re your current problem, I would go through normal troubleshooting steps. I would attempt to get back as much as possible to factory configuration to get a working backlight. Basically to find out if the inverter is actually dead.

The assumption you have been working to ( I think) is that the brightness of the backlight is controlled by a DC voltage. It is possible that it is a Modulated signal (like pwm fan control), or microprocessor control line, and a multimeter is just taking an average (guess). You need an oscilloscope to get to the bottom of this.

I remember mini hacks investigation of G4 CuBE power switch the extra signal to control the led, he couldn't resolve a simple DC control mechanism, so couldn't utilize the feature. My guess this was a micro controller signal. It is possible this is a similar situation.

Question: does the inverter have any chips with identify able markings, that could lead to a data sheet, which might identify the control mechanism?

Last thought. You have a second iMac with a working inverter, worst case you have a spare part, if you can't get the first one to work.

Kiwi
 
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Hi Kiwi

Thanks for reply.

The assumption you have been working to ( I think) is that the brightness of the backlight is controlled by a DC voltage. It is possible that it is a Modulated signal (like pwm fan control), or microprocessor control line, and a multimeter is just taking an average (guess). You need an oscilloscope to get to the bottom of this.
Yes, I assume that it is a PWM signal. I saw on the internet, that most of the inverters work with PWM or analogue regulated reference voltage. It is very strange, that it does not work either, if I wire it up like dremeljunkie and Ersterhernd did...

Question: does the inverter have any chips with identify able markings, that could lead to a data sheet, which might identify the control mechanism?
I could not find a valid chip identification on the photo... Maybe you can?

Last thought. You have a second iMac with a working inverter, worst case you have a spare part, if you can't get the first one to work.
The 2nd iMac did not yet arrive... The other possibility is to pull the CCFL out and to replace it with something like that: http://www.ebay.ch/itm/Ruban-bandeau-a-LED-Strip-30-60-120-LED-m-differents-coloris-et-tailles-/170894924170?pt=FR_YO_MaisonJardin_EclairageLumiere_Ampoules&var=&hash=item27ca21998a#ht_914wt_1413

What do you think?

MacTester
 
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It's working now - the dimming too!!! :D :D :) :)

Details will follow. :beachball:

Here is a short youtube video:

MacTester
 
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:clap:


Way to go, MacTester!



Ersterhernd
 
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