Reverse Engineering

Discussion in 'The Projects Forum' started by jgerwitz, Sep 18, 2006.

  1. jgerwitz

    Thread Starter New Member

    Aug 30, 2006
    9
    0
    What is the best way to reverse engineer a circuit board. I don't have a schematic and want to troubleshoot a problem with the board.

    Thank you

    Jeff
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Do you really want to produce a copy of the board, or make a schematic by following the traces and components?
     
  3. jgerwitz

    Thread Starter New Member

    Aug 30, 2006
    9
    0
    I only need to have a schematic for troubleshooting purposes. It is a circuit board attached to the instrument cluster in my Audi.

    Thank you!
     
  4. Papabravo

    Expert

    Feb 24, 2006
    9,903
    1,723
    The only way this will do you any good is to start with an inventory of the chips. If they are off the shelf parts for which you can obtain a data sheet you have some small hope of success. If not, you are wasing your time. If there are SOT-23 transistors or other difficult to identify parts then your chances decrease exponentially with the number of unidentifiable parts.

    Surely you have better things to do!
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    To amplify Papabravo, I had the amp in my car go out. I openes the case, and found that the four amplifier ic's were made bt STmicrodevices. Should have been no problem to get data, parts, etc..

    Not so, I found. The numbers were valid only for the contract with Ford, and do not cross to any part number in STm's current inventory. Don't be surprized to find Audi does the same.

    Plus - if any of the chips are microcontrollers, there will be a little program in internal rom running them/it. Most of those devices have a link that may be blown to prevent someone from reading out the code in order to clone the microcontroller.

    Much more trouble than it's worth - even at their inflated prices.
     
  6. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Paper, pencil, eraser, magnifying glass, good light, relevant data sheets, patience, a girlfriend muffler and ample supply of Scotch 'N' Coke does it for me ;)

    There exist at least one CAD program where you can scan the PCB (or snap a photo), import it, populate it and press a button, but I don't remember it's name right at this moment and doing it the hard is the best way to learn anyhow.
     
  7. jgerwitz

    Thread Starter New Member

    Aug 30, 2006
    9
    0
    Thanks to all for your advice.

    I do have much better things to with my time, however, little money to replace the circuit board. Maybe I will test the components that I can test with my meter.

    Thanks again, This is a very good site to be a part of.
     
  8. Chris Wright

    Well-Known Member

    Jul 26, 2006
    62
    0
    Would this be a VDO instrument cluster like the one's in the BMW's? If so there are companies out there that have already reverse engineered the boards and sell them cheaper.

    Here's a tip to keep from ending up with crossed eyes squinting through a magnifying glass trying to follow one tiny trace in a dozen:

    Take your Digital camera and set it to the max resolution (most pixels) and fill your view frame with the image of the board, you may have to use the macro setting if you have one. Open the image on your computer in a program that will display the image as "actual size", "pixel for pixel", "1:1", "actual pixels"(this is the PhotoShop cmd). The idea is to display only one image pixel for each monitor pixel.

    In my 4 Mega Pixel camera, the image is 2272 x 1704 pixels, and my LCD displays 86 pixels/in. so dividing 2272/86=26 and 1704/86=20 or it will display as a crystal clear 26in. x 20 in. image! It's better than a magnifying glass!
     
  9. jgerwitz

    Thread Starter New Member

    Aug 30, 2006
    9
    0
    Great idea!! Thank you.
     
  10. Chris Wright

    Well-Known Member

    Jul 26, 2006
    62
    0
    If your board is like the BMW, it may have a memory chip that needs a backup battery. Check for a dead battery on the board.

    It's always fun to watch the faces of people as they try to decide if you are pulling their leg when you tell them that to fix their speedo you need to change the battery in the instrument cluster! [​IMG]
     
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