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Cube Troubleshooting

bunnspecial

bunnspecial

macrumors G3
Original poster
May 3, 2014
8,353
6,497
Kentucky
One of my Cubes started giving me trouble the other day-specifically in that it's stone-cold dead.

This particular one has Sonnet 800ghz Cube processor and a 2MX video card.

In any case, plugging it in gives no LED on the VRM, and no response from pressing the power button. I've also tried powering it up via the display with the same response. I did do a PMU reset.

I've ruled out a bad power brick(traded with another Cube-the dead one is still dead, while the working one continued to work). I also did the same with the VRM, and confirmed that the "dead" one has a good VRM(and also didn't boot one borrowed from a working Cube).

I don't know where to go from here with trouble shooting. I think I've ruled out the common problems-can anyone suggest where to go next?

I should also add that this Cube probably hasn't been used in a month, but it was working fine the last time I shut it down.
 
temporarily forget what you know about computers and remember what you know about electronics. look carefully for a loose connection. an electrical test light may be useful. in other words make sure electricity is going where it's supposed to.
 
I don't have a cube close by to look at, but iirc there should be a LED on when it has 28v. Even if it's not turned on. So if there is no LED, I'd suspect the power brick, followed by the VRM.
 
flyrod said:
I don't have a cube close by to look at, but iirc there should be a LED on when it has 28v. Even if it's not turned on. So if there is no LED, I'd suspect the power brick, followed by the VRM.
Click to expand...

As explained above, I have ruled both of these out through part swapping.
 
So you are getting a LED lit up? Obviously you'd need the cube out of its case to see it...
 
It could be the power connector on the logic board then. If you have a volt meter, you could check the VRM to make sure it's getting 28v.
 
I can't believe I didn't notice this earlier, but had another look at it this morning and had a "There's your problem" moment.

IMG_2217.jpg


I'm going to assess the damage on it, but I'm guessing this one is beyond repair and will need a new LB. I'm just hoping it didn't take out my Sonnet along with it.

It would be nice if the Cube butchers(looking at one on here in particular) would save their logic boards, but I don't have high hopes on that. Looks like I'll be trolling the WTBs and Ebay.
 
Guess I qualify as one of your "Cube butchers", but more to the point, if the item in the photo enclosed is of interest to you, it could be had for the cost of shipping.
PM me if interested.

2016-01-07 10.31.06.jpg
 
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That explains why the VRM was not getting 28v. I'd be interested in that fried board if you're just going to toss it...
 
flyrod said:
That explains why the VRM was not getting 28v. I'd be interested in that fried board if you're just going to toss it...
Click to expand...

Definitely-let me get them swapped and I'll be in touch.

No point in tossing it if someone else can get some use out of it.
 
It's alive thanks to Jbarley!


IMG_2241.JPG


BTW, I'm not sure how it took me so long to find the problem. When whatever part blew, it REALLY blew. Aside from soot inside the top of the case, I found the below on my desk this evening

IMG_2242.jpg


Apparently when the part popped, it either shot flames out the bottom or the part that fell out was hot enough to do it. I'm NOT happy about the burn mark in the top of my antique white oak desk, but no use crying over spilt milk.
 
I'm glad you got it back up and running, without (?) collateral damage besides the desk.

I guess it's good that it wasn't near the drapes or something.
 
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