Shortcircuit between capacitor and heatsink

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mbonamusa
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Shortcircuit between capacitor and heatsink

Unread post by mbonamusa » Fri Jan 17, 2020 12:30 am

In the last few years I have found different XU4 boards that have stopped working for no apparent reason.
Now I think I have found one of the possible reasons. I think the capacitor C289 touches the bottom of the heatsink and can cause a short circuit.
I've noticed this situation in 2 boards.

I have attached some pictures to illustrate it.
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XU4_under_Heastink.jpg
XU4_under_Heastink.jpg (641.18 KiB) Viewed 236 times
XU4_C289.jpg
XU4_C289.jpg (363.07 KiB) Viewed 236 times

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Re: Shortcircuit between capacitor and heatsink

Unread post by rooted » Fri Jan 17, 2020 3:28 am

Why does the heatsink not have TIM?

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odroid
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Re: Shortcircuit between capacitor and heatsink

Unread post by odroid » Fri Jan 17, 2020 9:59 am

Thank you for sharing the pictures.
We will investigate the issue.

o_lampe
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Re: Shortcircuit between capacitor and heatsink

Unread post by o_lampe » Fri Jan 17, 2020 3:53 pm

I'd also be concerned about the solderball (just below the crystal) just waiting to move around and create shorts.
There might be many more of these little critters...

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Re: Shortcircuit between capacitor and heatsink

Unread post by odroid » Sat Jan 18, 2020 12:41 pm

The C289 is not an electrical component but a mechanical component.
It is only intended to help prevent the heatsink from tilting.
So there must be no negative side effect even it was damaged.
XU4.png
XU4.png (269.88 KiB) Viewed 125 times

mbonamusa
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Re: Shortcircuit between capacitor and heatsink

Unread post by mbonamusa » Mon Jan 20, 2020 5:26 pm

This mechanical solution is a good idea. Then I understand that this is not the cause of the board stops working.
What I find strange is that it has this short circuit mark.

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Re: Shortcircuit between capacitor and heatsink

Unread post by o_lampe » Tue Jan 21, 2020 3:28 pm

Did you check for other solderballs like this:
They can roll around on the board and cause all sorts of problems.
.
.
XU4_C289.jpg
XU4_C289.jpg (187.39 KiB) Viewed 43 times

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