G4 cube dead

Scorpio_ny · Monday at 2:36 AM

I was looking what you tried...any chance the video card developed an issue?

Fred1212 · Monday at 3:08 AM

Thanks done all the cleaning, checks etc thinking logic. I've replied to your DM cheers

Fred1212 · Monday at 3:37 AM

@Scorpio tested video card in G4 tower works.

Fred1212 · Monday at 4:00 AM

Just hunting through the junk box. I've a XPC7400 RX486PK, the cube has a XPC7400 RX450SK. Can I try this to see if its the CPU?
Also found a XPC7400 RX450PU

Fred1212 · Monday at 5:14 AM

OK bit the bullet and put the XPC7400 RX486PK in and miraculously it works. Looks like its only a 350mhz chip? but it is at least working. We'll see if it lasts

Fred1212 · Monday at 6:13 AM

And its dead again!! tried to install MacOS 9.2 started OK then froze and won't go again. I think its the logic board unfortunately

herd · 2026-02-17T15:55:13+0000

The 466MHz CPU board probably came out of a DA, so the speed in a Cube makes sense: 466 in a DA is 133 x 3.5, so the Cube with a 100MHz bus runs it at 350MHz.

Is temperature a factor? Is it more stable when cold? If you run it out of the case with the boards exposed, can you press on chips, flex the boards, slightly bend wires/connectors, etc. to locate the problem? Are the boards dirty/corroded? Contact cleaner on the various connectors may help. The 300-pin connector for the CPU is a bit fragile and its pins are easily bent or contaminated.

Also, I've worked on a few Cubes that had a factory bodge applied to a regulator, which runs very hot. Does your board have this bodge, and do the components look intact?

Scorpio_ny · 2026-02-17T16:09:51+0000

Here is a Hail Mary: in the past, many people reported the similar issues your are seeing and it was caused by a faulty power button. I believe there is a way to power it on with the power button disconnected. Have you tried that?

Fred1212 · 2026-02-18T01:06:50+0000

Power button seems to work but could be a problem? One short press switches the red led on thge logic on a lond press switches it off. @herd yes I'm going down the temperature route and the board does have the mod I'll have a look at that as well. Thanks everyone, appreciated

Fred1212 · 2026-02-18T06:15:11+0000

Should the light on the switch stay on . When I press mine the light comes on but then goes of again

herd · 2026-02-18T14:15:10+0000

The light on the power button should stay on. Does it stay on when the Cube does work? You can boot the Cube without it. Unplug the cable for it, and on the logic board momentarily short/bridge the two pins on the inboard side.

You can also boot the Cube without the ethernet, modem, and video card/riser.

I think that bodged regulator supplies 5v to the USB ports, standby power, etc. so it should show 5v with the Cube plugged in but powered off.

François · 2026-02-18T16:40:44+0000

IIRC there is two regulators on the main board: one for the USB 5V and one for the FireWire 12V. And on some boards, depending on the revision of the board, the regulator for the FireWire (I think?) has two diodes in series soldered directly to two of its pins.

I have a Cube board where the regulator for the FireWire 12V is blown: the Cube still works (except for the FireWire ports of course!) but it takes a very long time to boot, like several minutes.

G4 cube dead

Similar threads