iFixit - Answers With Device "Power Mac G4 MDD"

Power Mac G4 MDD: Power On, fans spin up, power light on 1 second then off

Fri, 22 Aug 2025 11:15:23 -0700

I recently acquired a Power Mac G4 1.25 MDD 2003 era machine. Top-notch cosmetics and I had plans for good Mac times here. But, instead my "new" MDD is suffering from this problem: 1) Attach power cable & DVI connection to Samsung LCD display & USB connection to Apple brand full size keyboard and the optical mouse; 2) Touch the power button above the mirror drive doors; 3) the power button illuminates for just 1 second and then immediately goes back off; 4) Fans spin up - low hum at first, and then the full "wind tunnel" effect; 5) no image appears on the LCD display, and the G4 does not respond to any keyboard commands; 6) I have let this G4 run for several minutes, but no change in the power light status and no responsiveness / output. I have reset the PMU, and did perform a full upgrade of RAM to 2GB OWC 333 MHz and dropped in a fresh PRAM battery. I have reseated the NVIDIA AGP graphics card. Looks like a trip to the 1 local Apple Specialist in a large Midwest metro is on tap.

⟐ Commented August 22, 2025 at 11:15 MST

Power Mac G4 MDD: I have a power problem on my FW800

Fri, 20 Oct 2023 20:55:04 -0700

Sorry for posting on such an old thread, but i have a power problem on my FW800. Started months ago, and i have swapped the power button board assembly and cable, then the machine started. But that didn't last long. After a short while same thing, and i swapped the second button board with the original, and surprisingly it all went ok for a little while again.

Current status is, pressing the button light comes on instantly, and that's all. My understanding is that all MDDs carry the same PSU? A tech guy suggested measuring amperage of the power supply. How do y'all measure voltages by the way? Is it correct that the psu needs to be plugged on the mobo?

Thanks in advance!

⟐ Answered October 20, 2023 at 20:55 MST

Power Mac G4 MDD: Is there a fuse for this?

Fri, 20 Oct 2023 10:16:17 -0700

My monitor cable came loose on a PowerMac G4 and then the machine shut off and won’t start again. Feels like a fuse problem but I can’t find anywhere that describes where a fuse might be?

⟐ Answered October 20, 2023 at 10:16 MST

Power Mac G4 MDD: What is PMU Reset button? for what it uses?

Tue, 01 Feb 2022 07:44:00 -0700

On my mac i seen PMU Reset Button, but for what is that? It’s like reset CMOS ?

⟐ Answered February 01, 2022 at 7:44 MST

Power Mac G4 MDD: Where do you fix or buy power mac G4 power supplies

Wed, 12 May 2021 03:39:39 -0700

how or where do you fix or buy power mac G4 power supplies, Samsung LQ3352ABPoWB, apple pin 614-0224

Sorry for the delay, just had world wind of unexpected etc..

Here is the pictures of the psu now finally removed from G4 MDD

add'l zoomed in pictures

do I need to remove fans so I can

lift up housing to get other view?

----- went ahead and unscrewed fans to get other views

⟐ Commented May 12, 2021 at 3:39 MST

Power Mac G4 MDD: How do I factory reset my power mac g4 med from the login screen?

Tue, 23 Feb 2021 19:11:39 -0700

My parents got this like 5+ years ago and I got it to turn on but the problem is that it stops me at the login screen. I saw many video on how to factory reset but it do not help.

⟐ Commented February 23, 2021 at 19:11 MST

Power Mac G4 MDD: G4 MDD Strange Graphic Bug

Sun, 08 Mar 2020 13:25:47 -0700

Hello! So I have an PowerMac G4 MDD which had a broken PSU, so I bought an ATX PSU and modded it so it works with a Power Mac G4 MDD. It booted up, pressed the ALT key on the Keyboard so I can choose an hard Drive to boot from and saw a very strange Graphic Bug.

The machine is responding and I can move the mouse cursor and such. What is the cause of this Bug ? Is the GPU broken? Or my modded PSU ?

Thanks in advance =)

⟐ Answer accepted March 08, 2020 at 13:25 MST

Power Mac G4 MDD: what is an I/F cable

Tue, 14 Jan 2020 04:41:13 -0700

check the I/F cable connection between the device and your computer.

⟐ Commented January 14, 2020 at 4:41 MST

Power Mac G4 MDD: G4 MDD freezes when CPU gets hot - why?

Wed, 31 Jul 2019 20:16:21 -0700

From a cold start the CPU (Dual 1.25GHz) temperature rises until it reaches over 50°C in about 40 minutes, when the G4 freezes. The HD remp also rises steadily to 35°C. I have to press the start button to shut it down.

I have cleaned all dust and fluff out of the machine, checked that all fans are working and replaced the heat sink grease and still it happens.

If I open the side door and use a small external fan to blow cool air over the heat sink the G4 operates normally for hours with the CPU temperature at a steady 35°C and the HD at a steady 26°C.

The technician (Apple Genius) at the local Apple Shop said they did not have the gear to check everything on such an old model

Mac, but all the sensors checked out OK and he thought the problem may be an ageing CPU. What do you think?

Roy Clark

rclark@bigpond.net.au

Sydney, Australia

⟐ Commented July 31, 2019 at 20:16 MST

Power Mac G4 MDD: Mac g4 mdd 1.25 ghz boots but no on light, no chime and no video.

Tue, 25 Sep 2018 15:23:34 -0700

I've had the PSU rebuilt. Replaced the battery. Changed the hard drive. Replaced the optical drives. Changed the video card. replaced the memory. Tried holding down the PMU and the on button for 15 seconds, no good. Pulled all the cables and held the on button for at least 15 or more seconds, still no good. What's left besides R&Ring the motherboard and or the daughter board?

⟐ Commented September 25, 2018 at 15:23 MST

Power Mac G4 MDD: Can I install osx tiger or snow leopa from my broken laptop onto this?

Sat, 25 Aug 2018 08:16:57 -0700

I have the installation disks and product key from the operating system that I installed on my now broken macbook pro. The install disks are for osx tiger and then later i purchased an upgrade disk to install snow leopard on that computer. I cant use that computer anymore due to hardware failure but I also own a power G4 MDD desktop computer which is only slightly older than my broken macbook pro. Will it work to install my operating system from the macbook pro onto the desktop device?

⟐ Answer edited August 25, 2018 at 8:16 MST

Power Mac G4 MDD: How to connect the fans from a power mac G4

Fri, 24 Aug 2018 05:02:45 -0700

I have the fans of a power mac G4 that I want to use to cool the inverter of my solar panels.

Can anyone tell me on which voltage they run and which of the cables to use. I just want to run them on fix voltage (12v DC if possible), and fixed speed.

thanks for the help.

Serge

⟐ Answer accepted August 24, 2018 at 5:02 MST

Power Mac G4 MDD: Which graphics card do you recommend?

Sun, 27 May 2018 10:05:30 -0700

i will be using my computer mostly for school work. i probably would use this in our studio 2 record music and edit videos and, also, i use youtube alot!

thanks

⟐ Answer accepted May 27, 2018 at 10:05 MST

Power Mac G4 MDD: cpu changeout, is it the cpu or motherboard?

Wed, 23 May 2018 04:58:13 -0700

I am a Mac newby by need of having run an old program on OS 9. I got a MDD, and after about a week, it will no longer start up. The light on the start button flashes, but nothing happens. I tried changing the the power supply, and that did not help, so I assume it is a bad motherboard or CPU. Any way to tell which? Last, what is the trick to release the CPU board from the motherboard? I have been checking this site, and have not found it. Thanks.

⟐ Answer accepted May 23, 2018 at 4:58 MST

Power Mac G4 MDD: will not recognize optical drive or extra hdd's

Sat, 19 May 2018 10:32:19 -0700

ill make it quick and simple had a problem with my g4 mdd not starting up properly, i would have to unplug from power outlet for it to start again , took psu to electronics repair guy , he replaced a capacitor ... worked fine for 2 days then again, i was about to get fed up and this on day i turned off my g4 with power button rather than thru finder shutdown menu , and voila it started normaly with button , i tried this several times and it didnt bother me any mor , recently changed memory and did it again, i reset with buton on MB and went on without prob , my issue now is after some time after first issue "power up" my g4 didnt wanna recognize my extra hdd's inside it , i have 4 hdd's inside it not to include the 2 optical drives , one a duperdrive dual layer and one a normal superdrive, ok after it didnt wanna recognize my 2 extra hdd's it started not recognizing my cd=roms ... what can it be , should i just quit fiddling with it and sell it on ebay ? its kinda heart breaking for me it been with me for a long time and its been wonderfull to me can someone give me some advice as how to fix this , apple suppor told me to buy a mb 499.98 thats moe than the g4 is worth :( plz advize , thx in advance

⟐ Answer accepted May 19, 2018 at 10:32 MST

Power Mac G4 MDD: Help with identifying components on logic board

Thu, 29 Mar 2018 14:40:22 -0700

Today I plug in my G4 mdd to the power and find a components (L15) is broken.

Is anyone able to identify it?

When I connect to the power, this components is sparking.

Thanks a lot.

⟐ Answered March 29, 2018 at 14:40 MST

Power Mac G4 MDD: Any advice on building this mailbox?

Sun, 04 Mar 2018 12:15:26 -0700

The front door of my freestanding mailbox fell off. Mailman says I need to fix it. The Mirror Dual Door seems to be to easier way to do it. Would need a handle on the door. Need to seal the back in from rain. Need to put in some means for a flag. Any ideas will be looked at!

This eliminates the problem of a sign for my business in a residential neighborhood.

Looking at the bottom box in the images here:

⟐ Commented March 04, 2018 at 12:15 MST

Power Mac G4 MDD: Sound not Working Neither on startup or in OS

Sat, 23 Dec 2017 09:43:42 -0700

I recently acquired a Power Mac G4 MDD in which the sound does not work.

I'm fairly new with Macs, so I don't know what to try

The speaker on the computer looks blown, but any external speakers I try don't work on any of the ports.

I've tried putting in an SB Audigy and Audigy 2, neither of them got picked up in Mac OS

The only resemblance of sound is a little speaker pop on startup

I'm stumped, can anyone help?

⟐ Answer accepted December 23, 2017 at 9:43 MST

Power Mac G4 MDD: Optical drive rejects all discs

Thu, 27 Jul 2017 06:34:33 -0700

I replaced the optical drive. The new drive does the same thing the old drive did. CD goes in, I can hear the drive trying to read the cd 4-5 times, rejects all cd in 1 min.

⟐ Answered July 27, 2017 at 6:34 MST