Convert Your MULTIMETER into an accurate SHORT CIRCUIT TRACER Finder for less than $1 Build This DIY

LER #204 Want a powerful easy to use Short Circuit Tracer but can't afford the price tag? Here is how to convert a multimeter into a powerful and accurate short circuit locator for less than $1!

Review: Vici 480C+ vs YR 2050 MicroOhm meters / short circuit tracers

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The Electronics Channel (live streams with Carlos and Detlef)

Gran Canaria Uncovered

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TEST METERS
ANENG AN8009 MULITIMETER
KAIWEETS HT118E MULTIMETER
VC480C+ MILLIOHM METER
MESR-100 ESR METER
XC6013L CAPACITOR METER

TM-902C TEMPERATURE METER
LCR-T4 COMPONENT ANALYZER
FNB58 USB ANALYZER
PCI POST ANALYZER
TL460S PLUS PCI_E ANALYZER
TOOLTOP ET120MC2 SCOPE
FNIRSI 1014D SCOPE
NPS3010W 30V 10A PSU
T12 STATION WITH M8 9501 HANDLE
M8 9501 HANDLE
YIHUA 982 Soldering Station C210/C245
FNIRSI HS-02 PORTABLE SOLDERING C210/C245
QUICK 861DW
PROS'KIT SS-331H

INFIRAY P2 PRO IR CAMERA + MACRO LENS
TOOLTOP ET13S THERMAL CAMERA METER
ET13S MACRO LENS
OPTICAL MICROSCOPE
TOMLOV TM4K AF FLEX
TL866 II+ PROGRAMMER
CH341 PROGRAMMER
NC-559-ASM FLUX

DESOLDER BRAID (I use size 8045)
HX-T100 SOLDER (0.6MM)
ESD-11 TWEEZERS

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Thank you
Richard

[pault]

So to determine the constant current you must divide 1.25v (Vref for the LM 317) by the desired current to determine the resistor value. I would choose 12.5 ohms exactly (15||75) then I know the circuit is producing exactly 100 mA. Then, the millivolt reading on the DMM can be multiplied by 10x to know how many milliohms the resistance is between the probe tips. This would be much more of the usage in my case. The nice thing is the circuit only uses the battery during test. Thanks for the idea.

UPDATE: I did this 4-wire circuit using the LM317 externally and it worked really well. Then I noticed one of my super cheapo multimeters has lots of room inside behind the think COB board. I proceeded to take apart a single cell power bank device then install the charger chip and the flat 800 mAh lithium battery inside the DMM, adding a hole in the side for the charger USB access and replacing the USB out connector with wires to the LM317. Also added a small light pipe to see the LED status lights for charging. I enhanced the constant current circuit described above even further with a 0.1uF cap on the input to reduce noise and a 47uF cap on the output for stability as I saw elsewhere, mounted this on a perf board. To finalize, I added a wire soldered rapidly very close to the tip of each lead, ran the lead down the side of the regular probe, and heat shrunk them along the pen grip. I also heat shrunk each current wire to the main probe wire with a 1 cm piece every so often to keep them manageable yet flexible. I would never use the 10A jack on this meter so I removed the terminal and ran these two wires into that, with a 2P connector to remove the leads. Now I have a modern portable rechargeable micro ohmmeter! If the 2P connector is detached, I can continue to use the remainder of the DMM features off the still-installed 9V battery.

[Ozzy]

I quite often just set the supply to 500mV and CC=100mA, connect probes with clips so you dont have to hold them, then quick calc the wattage, and determine if I need more current or not to slightly heat up the short (EG: 100mW is not a lot of heat). With the back of my finger (its a lot more sensitive), I feel around for the warm spot, if i cant find it, I turn the current to 200mA and repeat. If its a serious dead short, there is almost no wattage to heat up the short, and you need more current. If you find the area but not the component, rub a little rubbing alcohol on it and watch the first place it evaporates = short, been doing this 1982, good luck.

[CXensation]

Very good explanation on how to get better low ohms accuracy on your meter.
Never thought of that. Its so simple it even hurts ...
Your channel really needs a lot more attention from viewers.

[zedcarr]

You have well-earned my subscription. I have a board with about 100 74HC00 series ICs on it, and the 5 Volt power rail has a dead short on it.
I thought it was not even worth the trouble to cut PCB tracks to try to isolate the fault, but you, sir, may just have saved the day. 😁

[RetroUpgrade]

Brilliant video as always, love these kinds of (hacks) that make expensive tools available to the hobbyist.

[xAF]

I'm still cautious with the voltage. When I'm tracking down a short on a higher impedance signal, like an IO line, I still like to be careful the level of input voltage I'm using to drive the current source. If the short somehow opens while measuring, or I accidently probe the wrong net, I don't want to put 5V into a node that's only designed to take, say, 2.5V or 3.6V max. You're correct that in most cases, ICs will have a reverse diode in the silicon that will safely backfeed the current out to whatever internal VCC is used, and the low amperage won't be enough to hurt it - but, some devices are very sensitive. What I do is use an external bench supply rather than something like the LM317, and I'll set the voltage to 1V, or whatever the rated voltage of the shorted line is ... or lower if other signals nearby are lower level - I've never gone lower than 1V though. Then, I'll short the leads on the power supply and adjust the C.C. mode to the constant current that I want before I start measuring, then I "Kelvin" around the board with the highest resolution multimeter I have on hand. On large or complex boards, sometimes shorts are still difficult to narrow down, and when desperate, I've cranked the current up high enough into the shorted net that I could "feel" around the board for the warm component. (Not too high or you might burn you finger or melt a trace). It doesn't need to be a ton of current these days if you have a sensitive thermal camera. If anyone tries the higher current 'heat' method, I recommend that you keep the supply voltage lower in case the short opens or you probe the wrong spot. Good video!

[td]

I am so glad that you covered (in the second video on this subject) the information about not using PSUs for your power supply, because they have capacitors inside them. I would have surely missed this point. Meaning, I would have included the capacitors that the data sheet suggests to stabilize the operations of the LM317. Including those capacitors would have created a monster. It is very likely that it would have never occurred to me what the problem would have been.

[davidbrewer]

There are all sorts of ways to quickly find a SC component but this is a good one. Another old school way is to connect your bench supply on current limit for a decent but not damaging current, then dust a blast of freezer to the board. after a few seconds the white frost will melt on the hot components designating the thinnest parts of the current path including the short component which will thaw before the other parts.

[Qcorner]

Keeping it simple…love this kind of approach to trouble shooting. Gets my brain more engaged! Well done mate. Darrell - 🇨🇦

[hullinstruments]

Best thing I found is a “audible milliohm meter” like the EDS “ leak seeker”

seriously look it up if you haven’t seen one.

It’s basically an extremely fast and accurate low ohms meter that SINGS. It plays a different pitch as the resistance changes, even the tiniest changes in resistance. Like the difference in 1 mm of copper trace.

allowing you to track down shorts like nothing else you’ve ever seen. And I’ve got a metrology business doing test equipment repair and calibration… So I’ve got all the professional expensive benchtop gear… But I swear to God I grab for the EDS devices every day. Not only the leak seeker but also the cap analyzer.

Not affiliated with them at all, I’ve only talked to Dave the designer once or twice. Nothing to gain or lose and don’t give a shit if anyone checks it out… I’m recommending it only because of how much it’s helped me and countless others.



Like everything, it takes a bit of practice to get used to it. I like to compare it to a high-end Metal Detector or something like that… You can’t just spend a ton of money and expect it to work and interface with your brain instantly. Or like professional engraving equipment used by jewelers and Gunsmith. Or a fancy tattoo gun or something like that can spend a few thousand dollars on an engraving machine… But you still have to learn to use it and practice.

But with a little bit of practice it will be One of the most useful tools in your arsenal.

[rampak]

This is a very neat economical idea. There is one thing that reduces its usability: the way the connection is made means that you include any contact resistance between the probe and the circuit track in the measurement. Much better consistency can be gained by making separate connections to the PCB for the meter and the current source - i.e. two separate sets of probes, one for the meter and one for the current source. You could do this with double-pointed probes or just solder the current source leads to the board somewhere across the tracks that are shorted and then probe with the meter.
Regarding the over-voltage worry, you could place a silicon diode across the current source - this will limit the output voltage to about 0.6V.

[tunmyat]

Any thank you very much for your video about finding short in circuit because I am not E engineer but now can repair many things learning from yours. Thanks again.

[motojaknow]

You've build your own Kelvin clips. I've used the technique in a commercial armature testing machine with resolution of around 1 microohm. You can also use the technique to eliminate the metal junction voltages by either reversing the current or voltage probe polarity and resolve the unwanted junction voltages algebraically. Also, in automotive simple stuff, just use an incandescent bulb in series to regulate the current.

[orionRS]

6:41 For curious ones, this principle is also called 4 wire measurement. In combination with high voltage testing, 3-6 kV with low current, purpose is to test cable harness used in battery powered cars. In that way you can detect damaged cable, which will start fire in car.

[fredflickinger]

Very practical and worth is weight in gold when troubleshooting!

[maxwarfield]

Hello, I’m still a novice at electronics, so some of the stuff in this video went right over my head. But it was still, so interesting to me, that just had to subscribe to your channel, straight away. I’ve always found shorts, hard to find and this build of yours seems so simple and accurate. Additionally, believe I have the components to build this device, so I will have a go at it. Thank you immensely

[knightwar]

I've seen few videos of diy milliohm meter and this one is the most simple and easy to do i got an lm317t from an old dvb receiver and a 21ohm resistor, i will simulate a short circuit on capacitors in parallel and see what i get from my 3 digit dmm. Thank you for sharing this i appreciate

[romanstingler]

Richard, I saw this title and was thinking if you will build a oscillator/freq . generator and build yet another ESR meter :) Loved your ESR video ( All You Need To Know About ESR METER To Fix Stuff. How To Use Test Capacitors Inductors Short Finder ).
Keep up the good work.
Today I also fixed some mainboards and GPUs. Always interesting seeing other guys with the same hobbies/passion for the same things.

[BlakBawa]

Greetings sir. I would like to thank you and commend you for the great work you do. the way you present the content makes it very easy to understand concepts that were difficult for me in school. Be blessed and all the best in all your work.

[CasualInventor]

Thank you for making this 2-part video tutorial. I have built my own based on your design and it works remarkably well. The Aneng meter is a little hidden gem too!