An Amazing Find for My Next Project -- iMac G4 20"

[MacTester57]

Don't forget it!

 

[ersterhernd]

I don't know why I didn't do this yesterday when the screen was all taken apart, but I should've tested resistance to ground for confirmation of whether the orange inverter wire is a GND or not. Oh well, will do it later today.


Ersterhernd

 

[MacTester57]

I don't know why I didn't do this yesterday when the screen was all taken apart, but I should've tested resistance to ground for confirmation of whether the orange inverter wire is a GND or not. Oh well, will do it later today.

Good question. Are you sure, that the orange wire always has 0V? I you compare with my 17" wiring table below, you cash see that there is no On / Off (VEDID) wire. I assume, that the only On / Off signal for the backlight comes from the dimmer wire (Voltage below ca. 0.6V = backlight off)

MacTester

 

[ersterhernd]

Build Log 3 -- Prepare iMac and Test Fit 90W PSU

The Antec SNP90 arrived today, its very small. I cleaned out the G4 of all it's Apple hardware, mounted a Noctua NF-B9 case fan up top, and taped in the new Antec PSU for a test-fit. I need nearly 3" of space at the top near the fan to place the 24V step-up converter. As shown in the pics below, it's going to be VERY tight.



The iMac cleaned out

Noctua NF-B9 Case Fan mounted

Antec SNP90 Power Brick temporarily test-fitted with heavy white tape

So far so good. We will see if the step-up convert I ordered wil fit or not. May have to purchase a smaller one. Nonetheless, the Antec 90W power brick is a great product for this G4 project. Fits like a glove in there.


EDIT: I ordered a smaller Step Up converter that will definitely fit. They even ship to Canada which is a real bonus. Link below.

http://www.current-logic.com/shop/index.php?main_page=product_info&products_id=9



Ersterhernd

 

[ersterhernd]

Good question. Are you sure, that the orange wire always has 0V? I you compare with my 17" wiring table below, you cash see that there is no On / Off (VEDID) wire. I assume, that the only On / Off signal for the backlight comes from the dimmer wire (Voltage below ca. 0.6V = backlight off)

MacTester

MacTester, I tested the orange wire before I tore the machine down. It is NOT a ground wire, as it showed resistance on the mulitimeter when connected to a known ground wire. I couldn't find anymore info on it, so will have to give the CCFL dimming a try without it. Perhaps it will work, I hope so.

Cheers!

 

[kiwisincebirth]

Hi There you are going great guns on this one, I myself am not making much progress, my Nuc arrived yesterday, which is a good start so will update my thread shortly.

I thought long and hard about the original PSU. The vendor who sold me this machine told me that about 5 years ago it made a "POP" sound one day and he took it to the Apple Store for a PSU replacement. So the one currently installed is probably not as old as most in this vintage of machine. I figured that the odds of that happening again are probably higher with a G4 PSU than with a new 90W Antec brick. If I ever had to rework this project from a G4 PSU into a new model PSU it'd be a major re-think, so why not just use new hardware at the start? 90W should be plenty for what I'm going to do here anyway.

Understand you are well down your own path, but one of my justifications for reusing the original PSU was it specs. In your own case the G4 PSU is capable of producing around 190w if you only run it at 40w-70w (guess), the PSU is under no real stress so much reduced chance of failure. And if it does fail, you just have the replace the affected capacitors.

Anyway keep the updates coming.

Kiwi

 

[ersterhernd]

Happy New Year, Kiwi!

I kept my G4 PSU intact, in case I change my mind. It looks to be in excellent shape. I'm eager to see further progress on your G5. I'm looking for a low-profile sata cabling solution as well. Let me know if you find one.


Cheers!

 

[ersterhernd]

Build Log 4 - AC Power Loop

This build will use the original Apple iMac G4 power cord and AC input. The AC Filter inside the dome will be retained as well. Gone is the original G4 190W PSU, replaced by a 19V 90W Antec SNP90 power brick and PicoPSU WI-25-120 power supply. These pics show both the input and output flow of the power to the iMac.




Power Loop Diagram

Power Loop Completed

19V DC output to two destinations (NUC and PicoPSU)

Ersterhernd

 

[kiwisincebirth]

Have you seen jBergs posting on the inverter pinout.

http://www.dremeljunkie.com/2011/07/20-imac-g4-inverter-pinout-not-tested.html

 

[ersterhernd]

Have you seen jBergs posting on the inverter pinout.

http://www.dremeljunkie.com/2011/07/20-imac-g4-inverter-pinout-not-tested.html

Yes, kiwi I have. I grabbed the full technical spec document for the 20" panel from a link posted there too. JBerg didn't document anything about dimming the panel, looks like it'll be up to me to try and figure it out. Hopefully will succeed, time will tell.


Cheers!