How to Quickly Find and Trace PCB Tracks

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Introduction: How to Quickly Find and Trace PCB Tracks

About: I am a University of Edinburgh electronics engineering student.
This instructable will show you how to create a tool that will allow you to easily and quickly find and trace a PCB track. Whether you are creating a PCB or you are modifying or repairing it - this tool will save you lots of time and energy!

Stuck with finding a track on a multi-layered PCB? No problem! Here is the solution - quick, easy and highy affordable to make.

Why bother? If you use your standart multimeter probes and have to touch every soldered spot on the board to see if it is connected to the element you are looking for ... quite tedious and time consuming job. Using a piece of aluminium foil you will be able to search for PCB connections over a larger area which will minimise the time and efforts spent on that job.





Tools needed:
  • Multimeter
  • Wire (+ wire with crocodile clips)
  • Chocolate or a piece of aluminium foil
  • WIre cutter and stripper
Preparation

1.
Strip both ends of your cable. You need 2cm of exposed wire at one end and 4-5cm at the other end.

2. Take a piece of the aluminium foil and wrap it around the wire somehow. You need a piece foil that is at least 5 x 5cm large.
Now wrap the aluminium foil around your forefinger.

Connect the cable that comes from the foil to one of the multimeter's wires as shown using the crocodile clips.

Perform a test

Touch the second multimeter's wire to the foil on your finger. It should show around 0 ohms resistance. Redo the foiling operation if you see more than 15-20 ohms resistance on the screen. If everything is fine, you are ready to use the tool you just made.
Use the free multimeter's probe to touch a single spot on the board. Then using your finger with the foil move it over the components touching the soldered parts.

Thus you will cover more area quicker and when you hear the multimeter beeping - you have found your track on the PCB.

Finished

Now it takes a matter of seconds to find the tracks that connect the components on the PCB.

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    user

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    37 Comments

    It is a very good idea. We must however
    ensure that the electronic card is not powered and ideally that quite a while
    so that the capacitors have had time to be unloaded.

    No hope however that it works on tiny
    circuits as on smartphones. I tried and the components are too small and
    fragile.

    Thanks a lot for this great tip !

    Just found this. Another idea is to use a piece of conductive foam that comes with static sensitive components.

    user

    What everyone is saying about capacitors and sensitive chips is valid., but this is still a method worth remembering. I think on older, tougher circuits like power supplies, motor controllers, "dumb" slave boards and interface boards, this method would be very smart. I was working on one of my own circuits before, and a track was broken somewhere - if I had used this method, I would have saved a whole bunch of time.

    Obviously you need to be smart about where you use this, but then maybe that is where the rubber glove tip idea will come into play.

    Technically if your circuit is powered up and runnig ... well your first touch with the foil will create a rainbow or at least some sparks! This method is used on boards that are disconnected from all power sources.

    technically capacitors will store a charge and often it doesnt take much to destroy a semi conductor

    True, but in real world there is no such thing as a perfect capacitor, so there is a leakage current between the plates of any capacitor which means that it will self-discharge after some time.

    Also, there is the possibility that there will be a resistance across the capacitor's terminals, so it will dicharge reasonably fast even if it is charged from the multimeter's probes.

    a disposeable camera capacitor, cheap nasty short lifed capacitor, shocked me super hard after the battery was removed for over a year when i took it apart, so i completely disregard what you just said. Also, immediately after turning this thing off, many capacitors will still retain some charge, weeks after even, they will hold sufficient charge to damage delicate electronics or have the potential to corupt data or firmware on processors and/or memory hardware.

    Might try a finger cut from a tight fitting rubber glove for insulation, then the foil over that.

    And a short wire lead point on the nail, just sticking out a mm or two. Then you could sweep with the tip of your finger to find the area, then curl your finger a bit and pick with the point to find the trace.

    1 reply

    That is interesting ... you won't have to disconnect the probe when you find the area.

    You've got a good idea there (why didn't I think of that).

    Another way might be to have a ball-shaped conductive material, but soft, and apply that to the board. Tracing circuits can be time consuming and your method will speed things up.

    On the other end of the ball-shaped conductor handle could be an abrasive tool to rub off the green insulating covering on PCBs.

    You might even have a spring-loaded conductive ball mounted on a probe tip so that when needed the probe tip is a point or release the spring-stop (a little button) and the ball snaps into place down the probe tip.

    1 reply

    This looks like the tip of a pen or something similiar.

    Do you mean not to touch them right after you cut the power off from whatever the PCB is ... ot at all the time?

    Any high voltage caps have a + and - side, if you happen to touch a part of the circuit that is connected to the + side, while touching the metal chassis or while barefoot, the positive charge will seek ground through your body. It is wise to check larger caps by clipping an alligator clips from to your multimeter's black probe to ground and then probing capacitor leads with the red probe without touching the pcb, plus normal electrical precautions (one hand behind back, wearing rubber shoes). This applies to more high voltage appliations such as tvs amplifiers microwaves, anything that is electronic and uses a fair amount of juice.
    Be careful and if you feel like you dont know what youre doing, figure out how to proceed safely before diving in. A mistake could be lethal. Best of luck.
    Z

    (and yes this applies when the device is off and unplugged)

    I totally agree. I don't like lightnings in my fingers.

    Don't short high voltage caps with a screwdriver! Simply take a 100k/1w resistor (or something close) w/ two alligator clip leads and connect one side to high voltage power rail and other to ground. LEAVE IT CONNECTED while you work on your circuit as they will re-charge themselves if removed. You shouldn't need to think you have to discharge each one either, as they are usually connected through resistances and all should eventually discharge after a minute or so, or enough to get started on your tracing work. A golden rule though is "if ever in doubt, then short it out" before working on or near these.

    That's cool! I'd be more inclined to trust the wire brush (my luck usually involves boards with lots of flux residue or some sort of coating on them) but nothing beats foil for a quick hack.

    1 reply

    i agree but still a nice idea i made a wire brush adapter some time ago for my meter lol though i was the only one