grannyknot

repairing a circuit board

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    I started tearing down the instrument cluster today, PO manged to lose the clear plastic windows and looks like he installed an aftermarket tach, bent the speedo needle but the circuit board is the real problem. A leak at the bottom of the windshield has rusted the backing plate behind the board but also the copper on one of the lines has corroded and broken the circuit.  You can see where he tried to solder a jumper wire over top of the break.

    I was going to drill out the 5 brass rivets holding the board to the backing plate so I can remove the rust.

    Is there anyway to repair a circuit board?

    Thanks

     

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    For failures like that, typical SOP where I come from is to solder jumper wires over the damaged section (like the PO did), but do it with a little higher quality workmanship.

    That board looks simple enough that you could probably daisy-chain point-to-point wire the whole thing.

    Do you have a need to lay down new copper where the damaged trace is, or you just want something that works?

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    Clean the board well, then take of the damaged line(s) on the board and drill 2 small holes (1mm) at the ends of the line that has to be replaced and then put in a .8mm wire on the other side (componentside) of the board.  It will look good and work well 😉   (Make shure the board is clean for soldering, use good resin core solder tin. )

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    Use hot glue to hold wire in place. You can run a new wire along the top of the trace if you want a simple fix by connecting the pins at the end of the trace.

    I think there are 510 spares in the Z garage... pester me in spring when it is open again.

     

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    Well it wasn't as difficult as I thought would be, I'll just throw the backing plate into the bucket of stuff going to the platers.

    The tach was never hooked up and appears to be new or lightly used, it has 4 wires, red, black, white and green. Anyone want to guess which one goes to the ignition coil?

    I have a spare horn relay that I can use but I'm going to try some Evaporust to see if I can get this horn relay working again.

     

     

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    35 minutes ago, Zed Head said:

    What kind of car is that from? 

    510 I believe

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    Agreed. Repair looks fully functional. Might want to use something to pot that wire into place so you don't bump it or catch it on something and pull more of the PCB trace off the board. Hot glue as mentioned above, or an epoxy blob or two.

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    2 hours ago, Captain Obvious said:

    so you don't bump it or catch it on something and pull more of the PCB trace off the board.

    Thats why i gave the advice to put the wire on the component side.. as pro's do.. :beer:

    (i've worked with studer revox machines, and ones opened up a TEAC... wow, there are a lot of those wires in there! A ReVox is well engineered.. they don't do/need that!)

    Edited by dutchzcarguy

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    8 hours ago, Zed Head said:

    A service manual would have the diagram.

    It is an after market tach from I think 15-20 yrs ago and 510's didn't come with a tach unless it was special ordered.

    9 hours ago, Captain Obvious said:

    Maybe. Can you post a pic of the other side of that tach board? I can probably tell you which ones are power and ground.

    Here you go,

     

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    From those pics, I believe the black wire is ground side for power.

    Can you take the brass hex standoffs off and get a shot of the back side of the board? Is there enough slack in the tether wires connecting the board to the mechanical portion to spin the board over and get a straight on shot?

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    3 hours ago, grannyknot said:

    It is an after market tach from I think 15-20 yrs ago and 510's didn't come with a tach unless it was special ordered.

    The wiring diagram from the car the dash came from would most likely match.  Just saying.  If it was in a car then the diagram is out there.

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    Red is +12.
    Black is ground.
    Green is speed input.*
    White is gauge illumination lamps.

    *Note that I don't know what kind of signal the tach is expecting, but the green wire is where it should occur.

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    And... The smaller red and black wires leading deeper into the tach are what makes the gauge needle move. I can tell you more about that if there are problems, but I'm hoping it just works and we don't have to.   LOL

    Edited by Captain Obvious
    better choice of words. Reduce the obfuscation.
    • Like 1

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