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G4 cube dead
Posted by: Samuel_Saady on 2025-04-17 19:57:02
So, i hope theres another thread with a solution to my problem out there but i found nothing.

I got this g4 cube with the box and a psu for a great deal. Issue is, it wont turn on, When i press the power button, it lights up, then goes out and thats it. When i open the system up, the green light by the pmu is on and theres another green light on the pmu, but by the ram theres a red light thats on. When i leave it on for a while, it gets warm like its running like normal.

Theres no video coming out, and i dont have an apple monitor, but i do have a period acurate vga crt that i tried but nothing.

this is my first g4 cube, and id be sad to have to trade, because at the end of the day id rather have a working g4 tower than a dead cube.image.jpgimage.jpg
Posted by: Byrd on 2025-04-17 23:10:53
Reseat everything including the CPU, try known good RAM, new PRAM battery, test VRM
Posted by: Samuel_Saady on 2025-04-18 01:21:29
swapped cpu, ram, pram battery is at 2.9 volts, pressed cuda switch. not sure about how i can test the vrm though.
Posted by: Byrd on 2025-04-18 02:33:04
You're quick! I'd also check the PSU voltages, replace PRAM with new (it should be ~ 3.4V), and have a tinker with the power switch which can often be overly sensitive causing startup issues/shutdown.
Posted by: Samuel_Saady on 2025-04-18 03:35:16
ill swap out the pram with a known better one, the psu i checked with a multimeter, it was at 26-28 volts.
I dont think the power button is the culprit here, it detects when i press it, but the issue is that when i take my finger off, the light goes out, and the computer just does nothing. but when i press and hold the power button the light does turn on.

when i press the power button the cube appears to turn on(lights on the logic board light up), but the power button doesnt stat illuminated, and it appears nobodys home, and when i press and hold the power button for 5 or so seconds, the lights on the logic board turn off like a forced shut down.
Posted by: Samuel_Saady on 2025-04-18 13:18:39
Anyways, if i cant get this fixed by tomorrow, im thinking of selling this at swapfest
Posted by: Samuel_Saady on 2025-04-18 20:02:55
is there anyone else that has had the same problem before?
Posted by: Fred1212 on 2026-02-13 17:15:04
As above
I have a dead cube but the power supply seems OK , solid 28v and 12v and 5v on the drive power connector.
Power switch appears to turn on the main board as a red led comes on. Also get a green Led on the power board(should there be two?) No other signs of life. I've disassembled and reseated all the boards and the CPU but nothing. Video board dead? is this a thing with cubes? cheers
Posted by: Fred1212 on 2026-02-13 18:01:24
Hard drive spins up when power button is pressed but only if the ide cable is not connected
Posted by: herd on 2026-02-14 09:54:01
So the Cube powers on only when holding the "button"? Or does a single press (and release) power it on, and it stays on?
Posted by: Fred1212 on 2026-02-14 14:11:27
Hi herd thanks for replying. Single press switches it on, red light on AB and HD spins up if IDE cable is disconnected. Press and hold switches it off.
Posted by: herd on 2026-02-14 14:16:50
That is encouraging at least. Does the USB power up (LED mouse lights up)? You could try a pram reset with the keyboard, or potentially other keyboard commands like open firmware, target disk mode, boot picker, etc. Is there any indication that it's booting, like disk activity, or does it get an IP address if plugged into ethernet?
Posted by: François on 2026-02-14 15:13:28
Do you have the Cube speakers, or an USB audio module? It could help to know if the Cube will chime.

If you have an external FireWire drive with Mac OS installed, you can plug it in to try to boot with it.

And by the way, a long press on the power button will initiate a forced shutdown, by design. It’s the correct behavior.
Posted by: Fred1212 on 2026-02-14 15:51:17
Yes have speakers and get no chime. I'll try the external drive but have no video just black screen. No usb mouse light up. Doesn't appear to be booting at all as I said if I connect the hard drive to the IDE cable it doesn't spin up. Done PRAM reset.
Posted by: herd on 2026-02-14 17:15:39
Did you try the reset button?
Posted by: Fred1212 on 2026-02-14 18:32:58
Yes tried that as well
Posted by: Fred1212 on 2026-02-14 19:27:05
Some success did another PRAM reset and got to the flashing folder screen. Looks like the CDROM and HD are cactus so next I'll try a firewire cd drive.
Posted by: Fred1212 on 2026-02-14 20:40:08
And its dead again
For no apparent reason won't boot again.

I've not read anything about caps being a problem on cubes but is it a possibility?
Posted by: Fred1212 on 2026-02-15 17:53:57
A recap and still dead!!
Posted by: herd on 2026-02-15 18:27:00
Sorry to hear that. The CPU, video card, and RAM could be tested in a tower, but it sounds like the logic board is flaking out. You could try cleaning the connectors, sockets, etc. or look it over for possible damage, loose pins, corrosion, etc. I'm not sure what else to suggest. Good luck!
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