How To Quickly Find And Trace PCB Tracks

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.

Comments

[4lifenerdfighter]

Except for when the foil shorts two spots and fries your circuit...

[hertzgamma]

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.

[jpoopdog]

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

[hertzgamma]

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.

[jpoopdog]

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.

[aking14]

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.

[hertzgamma]

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

[Machine]

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.

[hertzgamma]

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

[galactify]

Don't touch any hi voltage capacitors!!

[hertzgamma]

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

[galactify]

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

[galactify]

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

[hertzgamma]

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

[jojokeo]

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.

[TheOneTrueStickman]

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.

[ansil]

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

[hertzgamma]

Yes, nice approach to boards coated with some protection.

[Ralph61]

What you really need is a service manual. The tin foil job seems very precarious but maybe not too bad as long as there is no power on or residual power from charged Capacitors and a few other things, I suppose there is some resistance in the foil making it less susceptible to direct shorts. I one time was trying to find a problem on a Circuit board so I wanted to use the same or similar method he was using except just the meter and leads. I had it on before and did some trouble shooting with oscilloscope and found the area but not the problem So I decided to try using the continuity test method. What I forgot to do was discharge all the capacitors or at least the higher voltage ones. I left a lead on ground side of a higher voltage capacitor and touched a component near a IC and it blew the IC. Fortunately for me it was a TV the another service technician couldn't find the intermittent problem and was going to junk it, He gave it to me and said good luck. I had the worst kind of luck. When using continuity you should always discharge the high volt Caps. for sure even if you just cross the plugs contacts it will sometimes Get rid of residal voltage but not always You can just short across them with a screw driver or put a wire form positive to ground and keep fingers clear. Sometimes there is a high voltage snap that can make you jump. Maybe that is a better way using foils as it may discharge most capacitors on its way.

[hertzgamma]

I see your point, this is all good to know and take account of. The foil method is good for fiinding a relatively small area on the board - not the precise component, as seen in the video I posted.

And for sure, the hi-voltage capacitors are dangerous, in fact all capacitors produce great currents and sparks when the terminals are shorted which may cause problems in processors and IC's and many other components. I usually leave the boards for a long time to allow capacitors discharge safely.

[Phil B]

This is very interesting and will be very useful the next time I need to do something like this. Thank you.

[hertzgamma]

Please vote for me in the Electronics Tips and Tricks contest if you want to support me in the contest.

http://www.instructables.com/contest/etipstricks/?show=ENTRIES&sort=HITS_TOTAL

Thank you!

[somnonaut]

Side note, that is why making a simple piezo signal + 1 AA battery "closed circuit finder" is so important to any shop. Much less costly than an alarming voltmeter.

[hertzgamma]

This is also very good tip! Especially if you have a rather slow multimeter and it does not beep when the contact is too short.

But eventually you'll have to confirm that the resistance is 0 ohms, so you'll need a multimeter.

[bpfh]

Great idea. This would have saved me a few hours on some repair projects! Well thought!

[hertzgamma]

Thanks!

[saad_3122000]

This would have saved me a few hours on some repair projects Thank you.

[emerson.john]

A clever tip. Thanks!

[Lt.Greg]

Laddie --- Feirst ya hov ta explain for those of use who are nut electrical engineers, just wot the bloody heck a "PCB track" IS! We may not hov ta use it fur ena-thing, but we would like ta at least know sumpthin aboot it!
:-)p

[cheddar.alan]

Now why didn't I think of that. Doh!

[MikB]

An alternative idea: Get hold of a steel or brass wire brush and use that for the "alternative probe".

I have a "proper" WaveTek Meterman SF10 short finder. It has a flying lead with probe, like a meter. The other end is either a fixed probe on the body of the tool (precision) or a wire brush at the other end (blunderbuss approach!)

It really helps if your multimeter has a beeper, as relying on just the display is TOO SLOW!

[hertzgamma]

Yes, this is another option.
About the multimeter beeper - there are so many multimeters available and their cost ranges a lot, so does the response speed vary. I use a Fluke 179 and have no problems with that, but attention should be paid with other multimeters that respond a bit slower and sometimes a quick touch of the probes does not make the beeping sound or does not show the correct resistance.

[MikB]

Yes they do vary -- I find most digital (and analogue) multimeters are too slow to catch that momentary contact as you sweep a board, it's literally there and gone before the display has updated. It's also handy to keep your eyes on the board, not the meter.

Beepers all the way!

[balddemon]

No doubt it is a very usefull tip, Tanks fo sharing