Author Topic: Power board 1708 part burn it  (Read 781 times)

Offline zis2104

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Power board 1708 part burn it
« on: August 18, 2021, 04:51:22 PM »
C8,C6, D23 and R91 or l2 are very damaged.
https://ibb.co/BTp98qY
https://ibb.co/VYWBYW0
Can tell me name and value of part?

Update...i have see now schematic  and only D23 and R91 i don't known what it is.
« Last Edit: August 18, 2021, 05:15:55 PM by zis2104 »

Offline RDC

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Re: Power board 1708 part burn it
« Reply #1 on: August 19, 2021, 01:43:31 AM »
L2 is marked R91 because it's the value of it. R typically means a Decimal on components like that. So the R91 means it's 0.91uH. Another example is L3 and L4 on the board there, the are marked 4R7, for 4.7uH. You'll see that on some Resistors here and there as well, where 2R2 means it's value is 2.2 Ohms.

D23 is some kind of Schottky diode. You could toss just about anything in there and it would work though as it's just for keeping anything from getting back onto the USB 5v rail.

Check the values of all the Resistors around there while you're at it, to make sure nothing has gone way out of spec. Some of those are precision Resistors and having them be off even a few Ohms in value would effect how that circuit Regulates the 5v down to 3v for U2 and U3 to use.
Screwing up is one of the best learning tools, so long as the only thing you're not learning is how to screw up.

Offline zis2104

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Re: Power board 1708 part burn it
« Reply #2 on: August 19, 2021, 06:03:50 PM »
I can take parts of replacement from power board 1697, but now my question on bottom board, the short on 3.3v rail how i can find them? U2,U8,U9, J5 are the suspects.

Offline RDC

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Re: Power board 1708 part burn it
« Reply #3 on: August 19, 2021, 07:19:45 PM »
The 3.3v goes to far more than just those. Use a benchtop PSU and inject 3.3v onto the 3.3v rail and find out what gets hot first.
Screwing up is one of the best learning tools, so long as the only thing you're not learning is how to screw up.

Offline zis2104

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Re: Power board 1708 part burn it
« Reply #4 on: August 20, 2021, 02:27:38 AM »
some resistors and caps seem a little blackened to me ... I try to change those first
« Last Edit: August 20, 2021, 02:50:57 AM by zis2104 »

Offline zis2104

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Re: Power board 1708 part burn it
« Reply #5 on: August 20, 2021, 12:12:13 PM »

 

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