G4 Cube freezes after a while

Wouter3

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Oct 31, 2017
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I am running a G4 Cube with a 1 GHz Sonnet CPU and an SSD on Leopard.
After a while the system freezes. The screen stays on but you see the small beachball turning and the machine does not respond to anything. I also see the light on the cinema display dimming and flickering. I have installed a fan so it should not get too hot. I had these same problems with Tiger. You can only switch it off and start again.

Do any of you have similar problems or do you have any ideas where I have to look for a solution to get this Cube a little bit more stable.
 

barbu

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Jul 8, 2013
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Any idea on the temps you are hitting? Should be OK with a case fan and an SSD, but it seems that it is not... I would also wonder about the health of the power supply and the DC-DC card since those are prone to failure. Perhaps inspect the capacitors on the DC card for bulging, leaking, etc.
 

Wouter3

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Oct 31, 2017
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Any idea on the temps you are hitting? Should be OK with a case fan and an SSD, but it seems that it is not... I would also wonder about the health of the power supply and the DC-DC card since those are prone to failure. Perhaps inspect the capacitors on the DC card for bulging, leaking, etc.
As my old VRM blew up I have installed a new one which is more powerful. The old one took the motherboard and graphics card with it, so those have also been replaced. The only thing that was not replaced was the little electronics board behind the power button.
Unfortunately you cannot install a temp program as the Cube does not have heat sensors. Although I think it is not too hot, this happens after half an hour the machine is running. I also had a situation where the running program is no longer responding, but I can move the mouse and start another program. But that goes as far as the jumping icons on the dock. I can also not do an Alt-Cmd-Esc to terminate the program. It simply is out of control.
This whole process ofter begins with the screen turning black and after a few seconds it comes back again. Then half a minute later it freezes, but with the screen on.
I had similar problems earlier, even running the stock 450 MHz processor, but then I discovered that one of the memory blocks was no longer recognised. When I replaced that it worked OK, so I assume it is no longer the memory which is at fault.
 

barbu

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Jul 8, 2013
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As my old VRM blew up I have installed a new one which is more powerful. The old one took the motherboard and graphics card with it, so those have also been replaced. The only thing that was not replaced was the little electronics board behind the power button.
Unfortunately you cannot install a temp program as the Cube does not have heat sensors. Although I think it is not too hot, this happens after half an hour the machine is running. I also had a situation where the running program is no longer responding, but I can move the mouse and start another program. But that goes as far as the jumping icons on the dock. I can also not do an Alt-Cmd-Esc to terminate the program. It simply is out of control.
This whole process ofter begins with the screen turning black and after a few seconds it comes back again. Then half a minute later it freezes, but with the screen on.
I had similar problems earlier, even running the stock 450 MHz processor, but then I discovered that one of the memory blocks was no longer recognised. When I replaced that it worked OK, so I assume it is no longer the memory which is at fault.
wow yes you had a similar experience to me. Blown VRM, toasted upgrade G4 and everything else. Someone bought the case from me :p I replaced it with an 800 MHz upgraded model (stock VRM tho) and it has run great for years. Good for you for scoring the VRM upgrade!
What about the Power Supply? Can you get it on a bench to be tested to make sure the power delivery is stable?
 

Wouter3

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Oct 31, 2017
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The VRM upgrades are still for sale from a company in Japan, cost $150 though.

If the powersupply would not deliver a stable 24 Volt, I assume the machine would not freeze, but switch off and restart. How would you test it, just with a multimeter?
And what can you do if it does not deliver a constant 24 V. New ones are not available and old ones might have the same problems.
 

barbu

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Jul 8, 2013
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The VRM upgrades are still for sale from a company in Japan, cost $150 though.

If the powersupply would not deliver a stable 24 Volt, I assume the machine would not freeze, but switch off and restart. How would you test it, just with a multimeter?
I agree with the part about it probably just shutting down unexpectedly, but you never know. A little fluctuation might be enough to just freeze it by starving the CPU of voltage for a moment.
Yeah I think a multimeter would suffice. Just make sure to set your range correctly. You'd need the specs for the PS as well, to make sure you know what numbers to expect. And you'd need to find out what each pin is for. But not insurmountable. Certainly worth a few minutes to verify one way or the other.
 

Wouter3

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Oct 31, 2017
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The 4 pins from the powercord are very close to each other and close to the shielding as well. I am afraid of creating a shortcut. I understand that replacement powersupplies are quite expensive
 

barbu

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Jul 8, 2013
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The 4 pins from the powercord are very close to each other and close to the shielding as well. I am afraid of creating a shortcut. I understand that replacement powersupplies are quite expensive
as long as you can get some fine enough probes, it should be ok. You could also insulate the pins you are not testing from the ones you are with some electrical tape or something.
I bet they are expensive, that's why I kept my old one as a spare ;-)
 

Wouter3

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Oct 31, 2017
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The fluctuation of the powerlight might also be an indication that there is something wrong with the powersupply after it gets warm/hot. I will take it apart and see if the capacitors in it are not leaking. It might even be easier from inside to test the voltage stability.
 
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barbu

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You would think that almost any part of the PS should be re-buildable with new components, unless it is multilayer PCB or something. Best of luck!
 

Wouter3

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The two clips one the side were OK. But the middle I could not get to so I used my Dremel and cut it open. The inside also looks as if everything is solid state. Doesnot look like it can be reapaired. All glued and covered with white putty :-(
 

Wouter3

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Thank you for sending the disassembly instruction. For me the two metal sides did not separate easily so I had to use some brute force. The inside does not make me very happy as all is glued together and I would not like to destroy it. I am not even able to measure the power output as all is very well stuck away as you can see in the picture of the instruction. I will look at it tomorrow with normal daylight.
 

barbu

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Jul 8, 2013
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The two clips one the side were OK. But the middle I could not get to so I used my Dremel and cut it open. The inside also looks as if everything is solid state. Doesnot look like it can be reapaired. All glued and covered with white putty :-(
I guess the "glue-it-all-to-hell" era started earlier than I realized :oops:
 

Wouter3

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Oct 31, 2017
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Rocksteady 28 Volt, so the PS looks OK. I will now look into replacement of the proximity power switch board
 

Wouter3

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Oct 31, 2017
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So am I. I will first try to up the fan a little, just in case the processor freezes due to getting too hot.
 

Wouter3

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Oct 31, 2017
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It stayed stable for a few hours and finally stopped. With the on/off "button" on the screen flickering. I openend the box and it didn't feel that hot. I started it again, it booted up and shortly after it stopped with the on/off button flickering again. It is most probably a heat issue, but I wonder whether it is the processor or something else. I remember when I had the 450 MHz processor installed I had the same problems albeit without the fan at the time. I think I might go for replacing the on/off button board. That is about the last component I have not replaced, after the monitor. I let you know :-(
 

barbu

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I remember people having problems with those switches, even when it was first released. I think some folks solved it with tape or something... I wish cube owner was still online, might be worth a spelunking through archive.org
 

Wouter3

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Oct 31, 2017
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I think I had this problem right from the beginning. I had hoped that people on MacRumors might have had similar problems and could point to the underlying problem.

In any event, I just ordered the proximity power switch new for €10 on eBay. So let's see how this works out.
 
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