Blown PSU

Discussion in 'General Electronics Chat' started by Goldie HDI, Jun 9, 2012.

  1. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    Hi Rifaa, I know this is a long dead thread, but I have a similar problem and was wondering if you could help me? I accidently connected 12v to the B- rail, and suspect a diode blown somewhere however there is no visibly blown component. I'm very embarrassed at having made this mistake. I would really appreciate your help. I have some technical knowledge, but not enough to nail this problem down. I have followed this thread all the way through with my dmm and found one or two differences in my readings, but I don't know what to do with this information, I really hope you can help.

    [​IMG]

    [​IMG]


    [​IMG]

    ps my wife is shouting at me for wasting our money on a psu and then blowing it up, if I fix it she might forgive me
     
  2. Georacer

    Moderator

    Nov 25, 2009
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    Greetings! And welcome to AAC!

    Your post, originally posted here (http://forum.allaboutcircuits.com/showthread.php?t=33613), has been moved into its own thread, where it will draw more responses.

    Please refrain from "hijacking" existing threads with tangent or off-topic questions. You can create new threads for new questions using the "New Thread" button on the upper left of the page.
     
  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I think you should start with the fuse F1 and then check D1.
     
  4. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    Hi, thank you for the quick responses, I used the original thread because I didn't want to pollute the forum with multiple threads on similar topics, but I must have been mistaken, so thank you for moving it.

    Hi Kubeek

    F1:- is fine (0 ohms)

    D1:- I'm not sure what to look for when testing a diode, I've set my dmm to diode, I get Overload in reverse and 0.15V in forward, is that ok?

    Thank you for your help
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Yes that is what I would expect for a diode.

    What is that red nasty looking thing in the top left?
    Can you make some more pictures so that the names are more visible, especially the left and right side?
    What are the names of the three terminals on the left? it seems to me that b- is not connected to anything, but i may be wrong.

    Did you try the psu after the accident?
     
  6. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    red nasty thing top left is a header for an external amplifier remote on/off, being in a car and subject to vibrations I superglued the plug in place... then had to cut it off again when the psu blew. I have taken more photos, these are the best quality I can get, the three terminals on the top left are +B, ACC and -B (top to bottom), so i should have connected the +B to the car battery, ACC to the switched 12V ignition and -B to earth

    Left Side
    [​IMG]

    Middle
    [​IMG]

    Right side
    [​IMG]

    Thank you again for your help

    Randomly poking around with a probe, I can see that B- is connected to numerous things, at least 3 pins on the PIC

    I have tried the PSU after the accident, The green LED on the right of the board lights up, but there is no voltage at J7 (big plug on right) or J2 (smaller plug on the right)
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Since it is an ATX and that tells me there is a remote controlled power-on, did you turn it on? Also, the green led tells me that the supply should be pretty much ok.

    How did you connect +12 to the -B terminal? Do you mean you connected -12 to +B and +12 to -B?
     
  8. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    I was rushing and connected the ignition (+12V) to the -B terminal, I also connected the battery +12V to the B+ terminal, and -12V to the ACC terminal. Yes, this system is remote controlled power on, so the board has a constant 12v and -12v, but when you apply 12v to ACC it should output a regulated 12V at J7 and J2.
     
  9. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Then the problem will be on the ACC connection, the rest should be ok. It seems to go only to the R8 on the left side, so check around there if the resistances seem ok.
    Can you get a better photo of the left side and underside without the foam?
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I just hate how they file off the markings on those chips..
     
  11. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    R8= 9.9k
    R9= 3.3k
    R10= 3.2k
    R11= 3.3k
     
  12. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I cant read the numbers so there is noway to tell if they are correct.
     
  13. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    I've tried to get a better picture, is this any good?

    [​IMG]
     
  14. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    except for r11 it looks ok, can you find if it is in parallel with something else?
     
  15. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    R11 doesn't look like it's in parallel with anything, one side connects to R10 and then to pin 17 of the pic, the other side connects to J6 (remote amp connection)
     
  16. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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  17. kubeek

    AAC Fanatic!

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    Cool, this looks like you can choose which source turns it on, can you use the glued remot to turn it on?
     
  18. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    not to my knowledge, the glued remote is supposed to turn the amplifier on /off a few seconds after the PSU powers up in order to avoid amp thump (to my knowledge), It didn't actually work when I tried it out though, so I just wired my ignition direct to the amp remote instead
     
  19. Goldie HDI

    Thread Starter New Member

    Jun 9, 2012
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    what else should I check?
     
  20. kubeek

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    Sep 20, 2005
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    Do you have an oscilloscope?
    That stuff on the ic, is it some lacquer or is it scratched deep?
     
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