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Author Topic: Replaced power supply, booted, now brick with no lights...?  (Read 2929 times)
vputz
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« on: July 30, 2010, 03:29:23 AM »

Quick question:

May be a lost cause, but I had a Sheevaplug with a blown power supply.  As with other folks, I hacked off the connector, swapped in a 5v power supply, and booted.  Success!  I was able to ssh in, play around, etc...

...for about 10 minutes.  And then it died; SERIOUSLY died.  Now I don't even get any LEDs.  I did notice a little grit around the backup battery.  Too late, I checked the power supply output with a multimeter and it was 5.2v, not a pure 5v.  Not sure how sensitive the components are.

So... anything to do but go through its pockets looking for loose change?
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guidol
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« Reply #1 on: July 30, 2010, 12:08:37 PM »

Didi you test another 5V Power Supply too?
How much Ampere did your replacement power supply deliver?

I thin 2 or 3 Ampere should be fine.

I dont think that 0.2V morr should be a problem....
Did you measure the 5.2V while the Plug is connected?
Some unstable power supplys drop the current if they are connected to a device but
give some Volt when no device is connected.

The power supply should be stabilized, like from a Router
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hanker
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« Reply #2 on: July 30, 2010, 02:17:07 PM »



I dont think that 0.2V morr should be a problem....



I hope not. Undecided I have a 5V 3A regulated power supply that I bought for the Sheevaplug for when/if its internal power supply dies. (I.e. not using it with the Sheevaplug yet.) I tested it with a multimeter, and it showed 5.15V.

vputz: yeah, I agree - try another 5V power supply, at least 2A. Also maybe reseat the connector on the motherboard.

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tylernt
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« Reply #3 on: July 30, 2010, 02:58:27 PM »

Testing the open circuit voltage of a power supply doesn't tell you much. You need to test the voltage while the Sheeva or something similar (like an appropriately sized resistor) is drawing current.

That said, 5.2v should be no problem. Low-voltage devices like this are usually specced for +/- 5-10%.

vputz what was the amperage of the power supply you used? If it's less than 2A, the Sheeva may be fine and you just need a better supply.
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vputz
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« Reply #4 on: July 31, 2010, 05:00:30 AM »

Good point--I looked at the specs and it was only promising 1.2A at 5V.  So that could be a problem, although as mentioned it booted up and ran fine for a few minutes using that power supply, so for it to now do absolutely nothing just seems weird. I tested with it connected, and the measured voltage on the bottom of the PCB (the "other side" of the power connector) showed 5.2V between the red/black contacts.

Another problem, though, might be related to this...



I'm not quite sure I understand what happened there, or whether this was new after rewiring the power supply or not (I would guess it happened in storage).  It certainly surprised me to see it, and I'm not entirely sure what to do about it.  Is this the sort of thing that can be cleaned up?  Not sure if that would cause the brick-ness I'm seeing, but worth a try.  I may have to unsolder the battery cage to get to it easily, though, grump grump.
« Last Edit: July 31, 2010, 05:18:11 AM by vputz » Logged

vputz
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« Reply #5 on: July 31, 2010, 06:11:58 AM »

Followup: this cleaned up pretty well, but doesn't do anything (at least with an underpowered power supply and no battery--which may not exactly be a shock).  I'll replace the batt and see if it improves, but the new power supply may wait until I'm back in the states; no sense buying a 240v power supply when I can't use it in two months.  I'd like to see at least the same signs of life I saw a bit ago, though.
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tylernt
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« Reply #6 on: July 31, 2010, 08:18:58 AM »

Good point--I looked at the specs and it was only promising 1.2A at 5V.  So that could be a problem, although as mentioned it booted up and ran fine for a few minutes using that power supply, so for it to now do absolutely nothing just seems weird. I tested with it connected, and the measured voltage on the bottom of the PCB (the "other side" of the power connector) showed 5.2V between the red/black contacts.
Again, open circuit voltage tells you almost nothing. Put a load on it and then test the voltage again, I bet it's way below 5V. It probably ran for 10 minutes until you stressed some component in the power supply to where it only supplies a fraction of an amp now, too little to power on the Sheeva but enough to fool your multimeter.

As for the battery, I've seen lithium coin cells leak from time to time. It just happens from age or manufacturing defect and probably isn't related to your power issues (unless the leakage has corroded some of the traces or components that supply power to the rest of the board).
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tmk
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« Reply #7 on: July 31, 2010, 08:47:59 AM »

Could it be that the battery made up the difference between the needs of the plug and the underpowered 5v source for about 10 minutes?

Total conjecture here, but it could be that the rapid discharge of the battery caused it to deteriorate.

-tmk
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vputz
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« Reply #8 on: July 31, 2010, 09:09:25 AM »

Again, open circuit voltage tells you almost nothing. Put a load on it and then test the voltage again, I bet it's way below 5V.

How much of a load can I put on it aside from "connect it to the plug computer board it was running on before"?  It's connected to the same board I was looking at, and I can't ask it to do anything more stressful than booting up because it's not even doing that.

Quote
As for the battery, I've seen lithium coin cells leak from time to time. It just happens from age or manufacturing defect and probably isn't related to your power issues (unless the leakage has corroded some of the traces or components that supply power to the rest of the board).

Well, at any rate I cleaned everything and replaced the battery, but no luck.  This may just go back in storage until I can replace the power supply properly.
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birdman
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« Reply #9 on: August 03, 2010, 05:45:23 PM »

but the new power supply may wait until I'm back in the states; no sense buying a 240v power supply when I can't use it in two months. 
All the switched-mode supplies I've bought recently run on 100-240V 50/60hz, so you'd be fine (but would need a suitable pin-adaptor for US-running.
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vputz
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« Reply #10 on: August 15, 2010, 09:44:27 AM »

All the switched-mode supplies I've bought recently run on 100-240V 50/60hz, so you'd be fine (but would need a suitable pin-adaptor for US-running.

Found one as you described, which would work on 120Hz... switched regulated power supply rated up to 3A... still dead.  I think this one may have given it up; I don't know anything else to try.
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andebkr
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« Reply #11 on: September 24, 2010, 10:51:15 PM »

In some cases the batteries so get flared up while using some extra power which could be seen in the picture shown above. I did have a similar experience sometime back. You need to be pretty sure of the figure here as this is indeed something that would be of the utmost concern.
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