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Fried RPi2

e14 Contributor

I hope this is the right place to ask this question.

 

I am a total noob at the RPi and prototyping.

I made a dumb move and connected a 8xaa (10.39V - rechargeables)

to my ULN2803a to drive a stepper motor

 

The RPi fried.  I see a split/bulge on D5 (it definitely let out the magic smoke).

 

I see some suggest that you can replace that part SMBJ.05A, but when I go

to the element14 store, there are many choices for that one part.

 

Anyone else attempt this?  Major bummed and willing to try to fix it.

 

Please be gentle, I know my mistake and am new and want to learn.

  • 0

    That SMBJ.05A part is hereSMBJ.05A part is here. You could remove the part and connect the correct supply, and see if the board

    functions (it is a protection device, not essential to operation provided you use the correct voltage).

    If it does function, then great, and you can buy a replacement part. If it doesn't function there is further damage,

    most likely beyond repair.

     

  • 0 in reply to shabaz

    Thank you image  I appreciate your time and response.  I don't see a link.

    For removal, I assume you just heat up the solder with solder gun and remove?

    I ordered another Pi because there was immediate withdrawal.

    If it is not repairable, would it be good for spare parts later?

  • 0 in reply to e14 Contributor

    I think you have to read the comment on the website (not in an e-mail) and expand the comment fully to see the URL appear, because it was in a hyperlink. This is the URL: http://uk.farnell.com/littelfuse/smbj5-0a/diode-tvs-5v-uni-smb/dp/1456972

     

    Do you mean desoldering gun like a heat gun? If so, then perhaps, but I'm not comfortable with them so would be tempted to just use a very hot soldering iron on both sides alternately until there is enough heat transferred to lift it off with tweezers. It's not necessarily good practice, can damage pads.

    If you're going to use a heat gun, practice first on scrap PCBs on any component.

    If you really mean a soldering gun, I've never used them, they don't have much place in electronics I think - most people use soldering irons.

    Regarding spare parts, there is not much that you could want to replace by hand, so the board is pretty much unusable I'm afraid. There is nothing of value worth removing from it that could be done without further damage.

  • 0 in reply to shabaz

    gun ... iron ... LOL... I believe it an iron.  I don't think I will mess with it at this point, but I have bookmarked the part to purchase when I do.

     

    You may know... is there a way to put something between the pi and batteries that protects it from back feed.  I am new and don't quite understand this stuff.

     

    I had the ULN2803a on the breadboard with the power connected to pin 9 and the stepper motor wouldn't move(not even any indication or vibration when you put your hand on it

     

    Somewhere I read that you could put a three pinned diode(?) that would not allow current to flow if the polarity was accidentally reversed.  But it would be nice if I could have that safety mechanism always in place to ??decrease?? any power going back into the board and thus back to the pi.

     

    Got my new pi... booted right up ... happy again!!

  • 0 in reply to e14 Contributor

    More on this... tested with voltmeter and reading is 5.39V (pp2 to pp5) which is just above normal range at 5.25V.

     

    I also noticed that F1 gets extremely hot.  Would you happen to know a part to order to replace that? 

  • 0 in reply to e14 Contributor

    There is no publicly available parts list. It is a closed hardware design.

    It _may_ be mnfr part number MF-MSMF200 (according to an early revision schematic that raspberrypi.org were careless enough to publish on the Internet) but it is a guess. If you want that part, it is available at farnell.co,uk.

    If you're reading 5.39V then either the voltmeter is very inaccurate or the power supply is faulty, it should be around 5 to 5.25V.