G4 Cube revival help?

[TJ812]

I picked up a complete, cosmetically nice Cube this weekend for very cheap. The seller was the original buyer and had photos of it booting within the past few months. The final FB listing said 'it does not currently boot' and it is 'likely the hard drive as it was making some odd noises'.

I included the matching monitor, speakers, PSU, etc. All cosmetically near perfect.

I have several old Macs and other vintage computers which I've revived, so I thought this would be a fun challenge.

But this Cube is, in fact, not booting.

Symptoms: power button LED will light bright and then flash off and on slowly. there is no sign of video out from the Apple monitor or from a VGA monitor.

What I've tried so far: replaced PRAM battery, pressed the PRAM rest button, reseated RAM modules, disassemble to the point of removing VMU, video card, modem card, and reseated them all. disconnected the drive power connector with video card/modem/ram removed, same flashing power.

The power supply brick seems ok and is steady 28vdc on both sets of pins. the DC on the drive connector on VMU shows near nothing. My guess is the power module VMU.

Any tips on what else to look for?

Thank you.

 

[phunguss]

Here is a maintenance manual. It does not sound like yours are "flashes" as they are defined as 1/4 second. If it is slow pulsing, not sure what that could be.

• Two Flashes: No memory is installed or detected.
  • Troubleshooting: Make sure the RAM is securely in its slots. If no memory is installed, install the correct type.
• Three Flashes: Incompatible memory types are installed.
  • Troubleshooting: The Cube only supports PC-100 or PC-133 SDRAM, not ECC or registered memory. You can identify incompatible memory by counting the chips - an odd number suggests it's incompatible. Remove the incompatible memory.
• Four Flashes: No memory banks passed testing.
  • Troubleshooting: This could mean faulty RAM or memory slots. Check for bent pins on the logic board's memory slots and contact Apple for replacements if needed. If there are no bent pins, try resetting the logic board by removing the video card and pressing the S1 reset button

 

[François]

Did you test it outside of its enclosure? The power button is very finicky, and sometimes detects a touch when there is none. When a normally functioning Cube is put to sleep, the power led pulsates slowly, like the slow breath of a person sleeping. The problem might be the power button malfunctioning and the Cube goes to sleep directly?

 

[TJ812]

Did you test it outside of its enclosure? The power button is very finicky, and sometimes detects a touch when there is none. When a normally functioning Cube is put to sleep, the power led pulsates slowly, like the slow breath of a person sleeping. The problem might be the power button malfunctioning and the Cube goes to sleep directly?

Thank you both for your replies.

I have the bottom switch panel loose and unscrewed.

Mine is missing the grommet around the button, but I read that is ok.

is it possible to trick the unit via the connector to power on for testing, bypassing the switch?

 

[ScutBoy]

Since it seems you have one of the matching acrylic displays, you should be able to use that power button even if the one in the Cube is disconnected.

 

[François]

Do you have the USB speakers? Does the Cube chime?

 

[Scorpio_ny]

When you power on the Cube, do you see a green light when you look into the vent (or with the case off)? That should be the VRM board. If you do not see it could be an indication of power. Another trying to check is the PRAM battery. If you can, check the voltage. I faulty battery could cause some issues.

 

[TJ812]

the power LED on the original subject VRM glows a light orange.

I received a second Cube a few days ago. #2 does power up, the VRM LED is bright green. #2 Cube boots with video! neither HDD works, and neither DVD drive mechanically functions (ejects/loads) properly. I'll try to work on the DVD drives to get them working.

Most importantly, I'll try to swap some parts to see if the #1 VRM is to blame.

I'll post back with findings.

 

[TJ812]

I got a cheap SD-to-IDE adapter set up and booting 9.2.

I'm still struggling with both DVD drives and basic insert/eject mechanics (using only an ATX power supply for power testing). that DVD drive is finicky.

 

[phunguss]

View attachment 22342

I got a cheap SD-to-IDE adapter set up and booting 9.2.

I'm still struggling with both DVD drives and basic insert/eject mechanics (using only an ATX power supply for power testing). that DVD drive is finicky.

You may have to disassemble those original DVD drives and lubricate/revive the rubber roller. Or abandon them and install a slimline slot load from an old iMac. See this thread.

 

[TJ812]

You may have to disassemble those original DVD drives and lubricate/revive the rubber roller. Or abandon them and install a slimline slot load from an old iMac. See this thread.

great thread, thank you.

 

[TJ812]

I have confirmed the original VRM in unit 1 was bad. swapped the VRM from my working unit 2 into unit 1 and it fired right up! I plan to order one of the tindie replacements when available.

but I also wonder what would be involved to revive my bad one?

 

[TJ812]

I was able to get one of the DVD mechs fully working. the front eject roller was loose on the rod...didn't seem right...so I used a bit of tacky glue inside (pulled back on sides, middle and inserted a drop). this made it grab much better. but when it finally worked was by cleaning the heck out of all the parts and removing the eject motor mount. then I got the mechanism to properly align by manually sliding it. once it slid/engaged properly, I put the eject motor and belt back on. it fully inserts, plays, and ejects now.

one of my other challenges was cable management with the HD/SD reader. I made a 40 pin cable extender about 6 inches to give me some room.

I popped in a music CD, plugged in the speakers, and it started playing! keyboard controls for audio worked. is there supposed to be a CD player app or control in OS9?

then I pressed keyboard eject and out it popped!

I've repaired my share of old computers (most much older than this G4) but this has been challenging and fun. Just need to get it reassembled.

and I have a second cube box which should work as soon as I get a VRM.

 

[Scorpio_ny]

That’s great! Soon you will end up with two working machines. Are you using that SD card adapter a temporary or permanent replacement for the hard drive?

 

[jasperman]

Lots of threads about VRM troubleshooting and some upgrades you can do on an existing card with new MOSFETS etc.