G4 cube ceased to work

[Cktwo]

Guys, I need your help. My G4 Cube has ceased to work from one day to another. It doesn't turn on at all. It has been working quite well with Sorbet Leopard. It's a G4 Cube with 1.5 GB RAM and a Sonnet 1.2 GHz G4 card.

What I have done so far, trying to solve the problem:
- Disassembled, cleaned and reassembled the machine
- Renewed the thermal paste between CPU and heat sink.
- Replaced the PSU with a new, compatible one.
- Have been using an Artmix VRM for a while
- Reset the PRAM (button on the logic board) and replaced the PRAM battery.

The system is using a fan to prevent from overheating. Currently it has a 80 GB hard drive installed, which worked fine (and still should).

What else can I do? Are the capacitors on the logic board prone to fail and need replacing (which I am unable to do)?

Thanks and a happy new year
CK

 

[ObeyDaleks]

Hey, sorry to hear about your troubles. Is there any sign of life? The original VRM has a green LED that lights up if the PSU is plugged in. Does the Artmix one light up? If not, can you try the original VRM? Is the VRM board touching anything, like the pillar?

If the PSU is confirmed good and the LED lights up, does the power button provide any feedback? Even a brief flash? If not, I would check both sides of the power button connector, make sure they are seated properly. Also, blow into it and clean it a bit. Those buttons are finicky.

You could also try unplugging the 12v connector from the VRM (I’m assuming it’s powering your CD, HDD, and fans). See if it works without those.

Those would be my first suspects - the PSU, the power button, and the VRM, in that order.

 

[Cktwo]

Thanks for your hints. The Artmix does have several LEDs, the first one telling me that it gets the required 28V, lights up. Nothing else happens though. I will check everything you mention but that will take me some time. I'll come back once I am done.

 

[Cktwo]

Well, it‘s back to work. The Cube had problems with BOTH its graphics card AND the CPU card (greetings from Murphy!). I was able to fix the graphics card with a friends help and had to revert to the 1.2 GHz Sonnet but at least it‘s now working again.

 

[Cktwo]

I gave the Sonnet Encore ST G4 1.8 GHz another try. But without luck. I installed the latest Sonnet firmware patch in advance (just to make sure) and the installed the card.

The computer turns on, after a few seconds (with me doing or touching nothing) the Power LED flashes quickly and then the computer resets. See attached video.

Any idea what could be wrong here? It works perfectly fine with the 1.2 GHz Sonnet Encore G4 I have used before.

Thanks guys!
View attachment IMG_2538.MOV

 

[ObeyDaleks]

As weird as it may sound, sometimes a simple pram reset works to get these new processors working. Did you try that?

 

[Cktwo]

YES!!! It works now! It WAS the darn graphics card. The pin seals had moved slightly, enough for the computer to not boot anymore.

Now, after recovering the pins again, it booted even with the 1.8 GHz card.

What I have done:
- upgraded the firmware to the latest version from Sonnet (just to make sure)
- replaced the HDD with a SSD (128 GBytes)
- installed 3 fans: One on the bottom that blows upwards, one on the top that sucks air outwards and a small one on the graphics card which is supposed to draw power from the Sonnets fan connector. This doesn't work yet and I don't know why. It is a 5V fan.
- of course, I have applied fresh thermal paste

From now on the only sensible strategy regarding the system will be: NEVER TOUCH A RUNNING SYSTEM!!!

@Mods: If you like, rename this thread to "G4 cube now works!". Thanks!

Thanks guys for your help and hints!