Hardware Cap above PI3USB shorted

Ace_

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The large capacitor above the PI3USB chip is shorted, I've tried removing the m92t36 and pi3usb chips but the short is still there, does anyone know what else might be causing it? This board had a damaged usb-c port and 5v obviously went some where it shouldn't as it smoked one of the protection filters and the pad to it and also a pad to the pi3usb chip which I think is the mode 1 pin.

edit: oh and the fuse was also bad, after fixing the above (before removing the two chips it charged okay).

edit: #2 To answer my own question, the cpu is shorted another scrap board. :(
 
Last edited by Ace_,

Pintglass

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Did you remove the cpu to determine that it was the cause of the short just curious as i have a board with a similar issue.
 

Ace_

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Everything but, although I did remove it on another motherboard and the short went away. The cpu doesn't seem to hold up to well to power spikes or liquid.
 

SolidSnakeUk89

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that large cap is only used within PI3USb, it is what goes between DP2+ and DP3+ as those lines need 100Kohm pulldown to ground.
if that cap is shorted, is usually cause PI3USB is shorted, try taking PI3USB off and check if it still shorted, if so, then replace the cap as well as PI3USb

DO NOT TOUCH THE CPU!

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just adding this for you:
upload_2019-8-25_21-2-42.png


upload_2019-8-25_21-2-52.png


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and here 3rd image so you see what that CAP does:

upload_2019-8-25_21-6-30.png
 

Pintglass

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that large cap is only used within PI3USb, it is what goes between DP2+ and DP3+ as those lines need 100Kohm pulldown to ground.
if that cap is shorted, is usually cause PI3USB is shorted, try taking PI3USB off and check if it still shorted, if so, then replace the cap as well as PI3USb

That Cap is on the 3v3 rail
 

Ace_

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^ yep, short is still there after removing the pi3usb and cap. I'm sure it's not always the cpu, so worth removing the pi3usb and crossing your fingers.
 

SolidSnakeUk89

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^ yep, short is still there after removing the pi3usb and cap. I'm sure it's not always the cpu, so worth removing the pi3usb and crossing your fingers.
hmmmm so if you take it off and the trail is still sorted then is time to check where does that trail goes.. check in a known good board for the 3v rail, there must be other places where this rail goes and there has to be something else shorted.

I have a similar case now with the 1.8v rail shorted and Im pulling my hair trying to find out where all the places where this rail is found lol
 

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