My pyboard is dead

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KihonNeko
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Joined: Thu Apr 05, 2018 5:40 am

My pyboard is dead

Post by KihonNeko » Thu Apr 05, 2018 5:48 am

Hi everyone!
My pyboard dosen't work anymore. The led isn't on and one component is very hot when i put my pyboard on. The IC with 8 pins at the bottom right of the microcontroller.
I think this component is broken but i can find is reference or name in the shematics.
Can you help me to find this component name or reference please?

Thank you.

torwag
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Joined: Fri Dec 13, 2013 9:25 am

Re: My pyboard is dead

Post by torwag » Thu Apr 05, 2018 7:23 am

Hi,

without looking into the schematic, I would say it is the voltage regulator.
The schematics can be found on github.
https://github.com/micropython/pyboard/ ... YBv10b.pdf

However, this is not a 8 pin IC.

Thus without a little more information it is hard to guess.

If it is indeed the voltage regulator you might have shorten the 3.3V line somewhere. Check carefully and try to measure the 3.3V at the 3.3V header. If there is no 3.3V you know why it is dead.
If you are luckly, you might find the short circuit and the voltage regulator did not take any damage. If there is no short circuit and it is indeed the voltage regulator, you have to replace it.

Good luck

KihonNeko
Posts: 3
Joined: Thu Apr 05, 2018 5:40 am

Re: My pyboard is dead

Post by KihonNeko » Thu Apr 05, 2018 8:02 am

Hi,
thank you for your response i have measured the regulator and he is broken(i measure 2.2V) But you have the wrong shematics i have a 1.1Pyboard .Can we send an image in this forum? Because i have a 8 pins component this is very hot when i put my pyboard on. this component is on bottom right of the micro like in this image(https://store.micropython.org/product/PYBv1.1#image2).

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pythoncoder
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Re: My pyboard is dead

Post by pythoncoder » Thu Apr 05, 2018 8:12 am

I'm pretty sure it is the voltage regulator. It's an MCP1703.

If it's getting hot the board has probably been subjected to an overvoltage or a reverse voltage. In either case the microcontroller could have been damaged.

I would remove the regulator, then apply an accurate 3.3V between the 3.3V and Gnd pins. With 3.3V and USB connected, if pressing the reset button produces a REPL then there's a chance the board can be salvaged with a new regulator.
Peter Hinch

KihonNeko
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Re: My pyboard is dead

Post by KihonNeko » Thu Apr 05, 2018 2:06 pm

thank you for your responses .
I have tested that on my PyB but there must be a short circuit because when i apply a 3.3V between the 3.3V and the GND pins i only have 0.3V @ 200mA ouptut out my power supply.

chrismas9
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Re: My pyboard is dead

Post by chrismas9 » Fri Apr 06, 2018 9:38 am

A 300mV drop is most likely a semiconductor failure. One way to identify the faulty device is to look for the point of lowest voltage drop. Measure the drop across every bypass cap and IC from GND to 3V3 with your power supply connected at the power pins. Say it is 300mV at the supply pins, 295 nV at the MCU and 290mV at the accelerometer then the accelerometer is more likely to be dead than the MCU. This is because the 200mA flowing between the power pins and the dead chip will cause a small voltage drop on the copper traces, especially on a 2 layer board. These drops are small but measurable.

The burnt finger test won't work because the regulator is dissipating 600mW and the dead chip only 60mW. There is probably nothing wrong with the regulator.

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pythoncoder
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Re: My pyboard is dead

Post by pythoncoder » Sat Apr 07, 2018 5:55 am

That's an approach worth trying. I'd also give some thought to the likely cause of the failure.

In general Pyboards are reliable. Random semiconductor failures are extremely rare. So I'd start from the assumption that the board didn't die: it was killed. The most likely cause of death is a reverse voltage or overvoltage on a pin. A reverse or excessive Vin might well take out the regulator; a failed regulator can sometimes protect the rest of the board from damage (in general - despite one valiant attempt I've not managed to kill a Pyboard). A bad voltage on another pin could wreck the microcontroller in which case I'd assume that the board was beyond repair.

So my suggestion of removing the regulator was based on the optimistic assumption that it had been killed but just might have saved the rest of the board.

An outlier as a cause might be physical damage or a solder splash/bridge (these can be very small and hard to see). It pays to inspect failed hardware very carefully with a strong lens before attempting faultfinding.
Peter Hinch

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