I was just searching to see how to put a multimeter to millivolts and seen this video. I finally see how diode measured to find if they aren’t working. Video is beyond excellent.
I have a digital ESR meter but I never know I could used it in other way just like what you did in this video. Thanks for sparing some time to share us your skills sir.
What a fantastic video! Over my self-educated time spent (100's and 100's of videos and some books), what no one ever said/wrote was that in repairing electronics, it all comes down to OPENs and SHORTs; with SHORTS being the "variable" cause ... meaning that there can be a SHORT ...or... a PARTIAL SHORT that's causing the problem. Once that became apparent, troubleshooting changed to "much easier" to diagnose. I have a Zapper, built a LeakSeeker, have injected voltage, and and and. This video from 7yrs ago ... I wished I had discovered earlier. It added a very valuable approach ... inject a small voltage and then look for a voltage drop in the mA's (or maybe even uA's if you can). Brilliant. Thanks for this video.
Thank you for the comment. It's always nice to hear when someone appreciates on of my videos. We had a period where bad capacitors kept repairmen fairly busy due to a manufacture error known as the "capacitor plague", but that's not so common anymore, so other than bad eeproms and leaky parts, I suppose shorts and opens do make up the bulk of repairs. All the best.
Great video !! And tips in the comments! When I first stared out in my 20's, my boss had a Weston 7 digit ohm meter to find shorts on boards. Boy did that work like a Champ ! 35 years later, I see this great idea using the mV meter approach !! Especially the HP concept in the comments !! I'm so grateful and embarrased I didn't think of it ! This concept in this video should get an award ! Thanks again for making this video and bringing out further comments here with further tips !
Also, if the short is low enough resistance, you can likewise inject a voltage of much less than the voltage than the power supply and boost the current output until the shorted component heats up enough to actually feel with your finger (no using expensive freeze spray. I work repairing cable boxes for Comcast and have been able to repair a very high percentage of boxes this way. I Have used the milli ohm method as well as the ESR Meter as well as injecting voltage and tracing with the milli volt meter, too. All have their place and merit. With Shorted chip components on a highly concentrated board with as many as 10 decoupling chip caps on a power supply line all across the PCb, it could be anywhere on the entire board. Hands down the injecting low voltage at higher current and merely feeling for heat is the most effective. I haven't had one case in hundreds of repairs where I have ever damaged the upstream or downstream components. This is mostly with buck supplies.
Thanks for this information. I would imagine a cheap thermal camera would help this process? I’ve had my eye on the “flir one pro” for a while now. at $400 I think it would be invaluable on the electronics bench, in automotive repair, even checking the HVAC/energy leaks in your home. A friend of mine has a cheaper model… And it immediately identified the bad wheelbearings on my vehicle in broad daylight because they were warmer than everything else. The flir one pro is pretty much the minimum priced thermal camera and resolution that one would want for electronics. Sure the $100 models work fine... but to really get down and see the smallest SMD packages and such… I think $400 is worth the extra price.
mister kluge Thanks a ton for the info! They’ve tried so many different terminal cameras… Are you referring to the “seek“ thermal camera? I know they’ve showed a few very nice thermal cameras but they are out of my price range. Closer to $1000....Where the flir one pro phone attachment is only about 400. And with a macro lens added… Can REALLLYYYYYY see tiny parts even the smallest SMD components clear as day. and the diy macro attachment is only a few dollars. AND makes small components 10 times clearer! Thanks for your time!
HULL GUITARS USA Did you end up getting the camera yet by chance? In a total novice with this stuff but I end up doing it often enough to make 400$ worth it, especially if it works for other applications. HVAC, home electrical, and car maintenance alone would justify it if it’s useable on a larger scale. I’d imagine it is, if it’s able to pick up the much higher resolution of electronics.
@@hullinstruments how about one of those cheap laser temperature guns? you could do the same thing with the low-volts high-current and scan the components. and those are like 30 bucks
Thanks much Grant you remind me of my uncle who had the 1st TV repair shop in the north Adirondacks.That was circa 1950? He was a communications guy in the Marines on Okinawa ww2
I'm a retired avionics tech. 30 years ago HP published a trick not unlike your own, using the mv on the DVM, but with no guessing. To find the short connect a current limited supply to the shorted supply rail at the spec voltage but with a safe current limit. Now connect the positive lead to the rail, and we'll use the neg probe to chase down the short. Clearly the millivoltage will grow towards the short, and if you probe past a node, the voltage will stop increasing.
That's how I used to find shorts until I got a $200 FLIR that connects to my phone. Now one of the first things I do is take pictures of the board temperature signature when I first power up the item. Sometimes it pinpoints the problem without any troubleshooting.
Short-Circuits (in their natural state) on PCB's have already done the damage to the equipment! I am an amateur (self-taught over 50 years). I can say that Grants Pass TV repairs have taught me that you can check out 'shorts' by the use of a DMM on the milivolt scale. I have followed the same procedure as shown in this video, and that is - to first determine WHICH CIRCUIT BOARD is faulty. Sometimes, there are five or six separate PCBs in a Home Theatre System. Narrow down the fault to just one specific PCB. Write down every step that you take! Magnification of the PCB and its' components is a must! Look for the obvious first. I do this by powering-up the suspect PCB independently, with the same voltage / current that is rated for the particular Board. I will not reduce the voltage (or current), because a 'short' is present. Remember that the Board cannot suffer more damage! At this point (when the suspect Board has been disconnected from ALL other Boards and Feeds), the 'short' begins to show itself........... Yes, components (even the printed copper track) will get warmer than others, because many other parts of the circuit are not being fed with their correct voltage - due to the 'short'. Have a smoke, have a coffee - but leave the suspect Board powered for 5 minutes. THEN, pinpoint every component such as diodes, capacitors, resistors, voltage regulators and transistors etc WITH A LASER BEAM. I am talking about the (very cheap) Hand Held Laser Pyrometer. The Laser Pyrometer detects the smallest amounts of heat (from or near to the shorted component), and you will definitely see results! As an amateur, I have had many hours of frustration and heartache in trying to detect a 'short'. I have no idea why all of the professionals have never mentioned this method of heat detection on You Tube. In many cases, it isn't possible to detect small amounts of heat with the human hand - from many components that have radically shrunk in size - and mass - from two or three decades ago. If I was a professional Electronics Technician, a Laser Pyrometer would be a very important part of my arsenal. Thanks to Grants Pass for a great Tutorial. Greetings from Australia.
Hi, I know it has been years since you made this post Could you be kind enough to provide me with how to locate any PCB power supply requirements and how to inject them for fault finding as you described in your comment above? Thanks.
@@solseyharbal-p9j What I said was that (to help find a short-circuit) you can use a Laser Pyrometer in a few instances. In any short-circuit, there will be a component on the PCB that 'has gone to ground", and usually, the faulty component will be drawing a lot more current than it is designed to do. My suggestion of powering the faulty circuit - and leaving it turned-on, was to (hopefully) allow the temperature of the faulty component to climb - and become much warmer that normal. A Hand-Held Laser Pyrometer will measure the temperature of the component - down to a tenth of a Degree Celsius. If you do find a component that is getting warm, then you disconnect from the circuit - and test it using standard methods. Sometimes, it may be hard to differentiate a "short" with an open - circuit fault - but (usually) when there is a "short" the circuit may be drawing more current than is normal. Every component on a PCB should have an Input / Output. I hope that this helps you.
A BIG thanks for your prompt & well-detailed response. You said ' " My suggestion of powering the faulty circuit - and leaving it turned-on, was to (hopefully) allow the temperature of the faulty component to climb - ". Did you mean, by using an external power supply or powering up the whole circuit board to achieve the above or that? Regards.
@@solseyharbal-p9j This depends upon how well that you know the PCB Circuit that you are powering-up. If you know the Input voltage to the PCB, and whether this is AC or DC - it helps. you could then use an external power source. If you do not have that information, then power-up by the 'normal' means. On Mains-powered equipment, I have frequently used a Variac, which brings up the mains voltage in fine increments. There are many components that will overheat, in a shorted-to-ground situation, but this of course largely depends upon the current draw. This method does not always identify a 'shorted' component on the PCB, but sometimes it does help. Sometimes, a Voltage Regulator may heat-up, and the Voltage Regulator may prove to be OK, but it is a fault further downstream - that the Voltage Regulator is feeding. There are many reasons, and (sometimes) it is a slow process to identify the faulty component(s). Hope that this helps.
Thanks for committing your valuable time to my questions, I am grateful. Sorry for the trouble and please, for the last time, I think I failed to convey my messages or questions properly please do bear with me for the last time. This is it; I wanted to know how to identify the voltage input/requirement of an independent and the separated ( having taken it out of the main or overall board already) PCB & how to power the PCB independently using and or applying your " home theatre illustration/experience. So, in simple terms, I want to know how to power up a PCB independently and also how to identify the amount of voltage and current needed to inject and where to. I want to be able to take a PCB out of the main board and how to inject the required voltage and current for a possible fault-finding based on your experience and the home theatre illustration above. Regards.
I’ve never tried testing diodes in circuit we were taught to always pull one side to open the circuit so no feedback loops. Good Information and well put together video! I’ll keep that trick on the shelf one day I may need it.
GREAT VIDEO & A GREAT LITTLE TRICK! My Teague ESI will measure down to micro-ohms, and uses a 4 lead shielded Kelvin clip lead set. That Teague is around $3000-$5000, used. The time it saves testing caps, & diodes in circuit are kind of worth it. I really love having it, and don't know how I lived without one as long as I did. I have used this method too. I liked the LCR bridge so much, I bought a spare one. It is a Chinese made no name that cost $700, but it works, despite only having 4 test frequencies, 4 test voltages & 4 test current. The Teague has 100s. I fixed up a Samsung plasma TV only to find it puts out excessive RF interference into the mains, making my amateur radio station noisy. Plasma TVs are notorious for backfeeding RF noise into the power lines.
You need to know something about the trace geometry to accurately pinpoint the short using this method. You need to measure the voltage drops across the traces. I start by connecting the negative lead of the DMM (mV mode) to the point where the current source's negative terminal connects to the PCB. Then begin probing further from negative connection point until the voltage stops increasing. As long as the voltage continues to increase, you are following the flow of current. As soon as it stops increasing and levels off, you've passed the short. If you have a layout viewer, it really helps. Using this technique with boards that have power planes is more difficult. You'll need a high precision DMM to measure micro-volts of change on top of the millivolt voltage that is actually across the shorted component. You may need 6-digits of precision to do this. The relative (delta) button won't help because the meter will use the appropriate scale for the total voltage ("trace voltage drop" + "shorted component voltage drop"). You are only interested in the trace voltage drop. I suggest using a good cad viewer that allows you to highlight nets and has coordinates so you can calculate distance. I've used this technique to get me within about 1/2 inch of a shorted cap between Vcc and Gnd on boards with hundreds of bypass caps on them. I also use thermal LCD paper and cold spray to try to locate the shorted part thermally.
In India, we mostly use rosin paste and 3.3v with few good range of amps (current) and volts depends to the supply line or supply track. And we easily find the shorting component. There are many ways to locate the shorting component and those are effective too.
another excellent video. although in my experience finding a short to ground is a lot tougher than you have shown especially if you have a bunch of smt noise caps or the short is between layers.
this is nice. thank you. I been back to watch this video several time. I also have the toneohm, which, I am in the process of making my own leads since its leads are crazy expensive, I am yet to learn how to use it though.. but I have found using a good thermal camera, though expensive but is a very effecting and fast way in finding shorts. I would call thermal camera, short finder for dummies.
Thanks very much for sharing. I too use my ESR meter for finding shorts but you've intrigued me with the short sniffer that I saw it costs quite an insane amount of money. 10 minutes later, I have one up and working just great, it's just a prototype of course but more or less I made myself and idea of what values of components I have to use. If you need any help, just ask. Cheers :)
Nice job. I'm working on a small board with a short somewhere. I'm going to apply a small voltage (3 D batteries, 4.5v) with a small current limiting resistor and try to get closest to the short with digital voltmeter readings OR allow more current and feel for a hot component.
very good most helpfull tip haow can you check for a winding short in a transformer do you have to use a micro ohm meter and know what a good one would read?
I do have a micro ohm meter, but when I test the primary side of a transformer I often use the my blue ring coil tester. Here is video on how they work. th-cam.com/video/Ky2T1-n_Fks/w-d-xo.html
91% IPA (isopropynol aka isopropyl alcohol)pour on suspect components then inject voltage and you will know what is shorted by how quickly it evaporates. Much cheaper than thermal cameras
Thank you so much. unfortunately, my bench power supply doesn't control current that accurately so I created a simple constant current supply circuit that I use now for this method.
Great video, thanks! There's a potential (little) goldmine out there if you can get the "throwaways" before the "scrappers". And if they are repairable. I bet most are.
I'm not sure I understand what you're looking for... Every measure you did had different values for different diodes. You KNOW one of the diodes is bad in this case, but the only indication you have for which one it is would be the one with the lowest value in whatever measurement you're doing. But if you don't know if it's a diode or a capacitor (or any other component, for that matter) that is the culprit, how would this help you? You haven't really located the short, because to even use the technique, you must know which component type you're looking for. And even then, it only works if all of the components of that type in the circuit has the same value. And even then, you can get "false positives" because of the natural difference in the readings.
This procedure is designed to help you find a shorted component where there are multiple components which share the same power supply output. it's not going to tell you if a diode, capacitor, IC, or transistor is open, but if one of these components is shorted such as a diode it will have the lowest voltage drop of all the components you test. I hope this helps.
I fixed my MacBook Air with this method. It had shorted component somewhere on the main power rail to ground. Supposedly, capacitor. But which one of many (about 100)? I put about 0.5V 1A to the board and then started to measure all capacitors to find one with the least voltage on it (because it will be the shorted one). And I found it! With simple cheap multimeter and power supply.
I think this is the most professional method to isolate the shorted component. I want to know about if this method can be applied to computer boards. If possible, can u make some video on that?
Great way to test for shorted components BUT that's IF you have more than one of the same component [with which to compare it with - like three similar values diodes]. But how can this work, when the components are of different values to each other AND altogether different components? Ex: a transistor, a cap [tear shaped - tantalum], an electrolytic cap, few resistors and maybe a diode. What can you possibly achieve test-wise with this method [ESR meter]? You would never be able to find the shorted component. But I have so much more to learn about electronics [I'm a complete NOOB in this field] so, PLEASE correct me if I'm wrong - I truly am trying to learn. Your videos have been a great source of education for me. Thank you kindly.
hi, is there a difference between a bad diode and a shortened diode when checked with a meter what i am asking would a shortened diode measure as bad with a meter ? thank you
I don't quite understand your question, but I think you meant to say shorted diode rather than shortened diode. ;-). When the short out they generally become like a piece of wire with almost no measurable resistance. Less than 1 ohm.
Never mind. I was thinking you could use Nano Siemens which can be used to measure very hi resistance. In this case your measuring very low resistance. My fault. Thanks
Gustav Kirchhoff would turn in his grave if he saw this video...... Those components are in parallel , the voltage drop across the components will be identical as you are measuring rail to rail. They will be passing different currents depending on their resistance but the voltage drop across the rails will be the same no matter where you measure. The more sensitive you make your meter readings, the more you will think that a few millivolts here or there mean something when they actually dont.. There is a reason why components in parallel need to be unsoldered to check, and this is a good lesson in why.
omgffsification Technically speaking the only voltage drop you really see in this example is from the shorted diode. The other diodes direction are not in the conduct mode, and capacitors do not pass DC. I should have used slightly different words to describe this example.
When diodes go bad they generally short out and their resistance goes down as the diode junctions become fused together. This test is showing me which diode has the lowest resistance reading within a few thousandths of an ohm.
There have been time in the past where I actually used the most simple and cheapest piece of test equipment I have. With a current limited supply and a little bit of current I used my finger to find who's getting hot... ;-)
We have a variety of ways to accomplish the same end result when looking for shorts to ground. Sometimes I use a lazier temperature probe, or I freeze spray the whole board until it turns white, and then watch to see which components are the fist to defrost. Louis Rossman made a video where he poured alcohol on his circuit board, and then watched to see which area of the board evaporated first.
LoL that is kinda funny, I thought you were gonna say where the alcohol starts sizzling... Yeah we are a creative group sometimes. More then most other groups....
Adhesive copper tape. Available everywhere, here is a link to one site that sells it, there are other sites, or outlets in your country as well. www.sparkfun.com/products/10561
Have any idea how I can force yt to put up your newest videos? I go out of town and upon returning yt seems to "retire" subscriptions to the back burner. I imagine just finding and watching a few is the only way.
Hey, you can just supply this troubled PCB not with ordinary high input voltage but with low voltage and high current capability power supply. And just use your fingertip to locate a shorted component(s) by its temperature. )) Any advanced multimeter needed, but ATC 300W power supply in tact is strongly recommended to have in your workbench.
+VINCENT ONGALA Most of the time you can test diodes which are in circuit, but sometimes you must remove them to know if they are shorted due to the surrounding components on the board . Anytime you remove a diode which appears to be shorted it's always a good idea to test them out of circuit to make sure your test results were not effected by surrounding components. Most of the time a shorted diode will have less than 1 ohm of resistance, so when I get a bad reading using the diode check function of my multimeter I switch my meter over to the ohms function so I can get more information about the nature of the short in terms of how much resistance the diode appears to have in circuit. If the ohms reading is 10 ohms or more I generally assume the diode is probably okay, but when in doubt pull them out to double test.
Yes. If you know where to test such as a positive power rail that should never have an extremely low resistance reading to ground. If you don't know where to test on the circuit board you can check for shorts across your capacitors. If you get an extremely low resistance reading it means you have a shorted capacitor or something on the circuit in parallel with the capacitor may be shorted.
I am wondered when looking at your demo when you turn ON DC power supply and connected to a short circuit that you made it by your own. I think it would feedback and blow power supply if you leave it for a certain time. THX,
Yes it could be a problem if your asking the power supply to deliver more amps than it can handle. My power supply can deliver up to 3 amps with out there being a problem to my power supply. If your power supply can't handle what ever current a short circuit produces, you can add a resistor in series with the device your attempting to repair. You resistor will probably get hot if your device has a short so you may need a high wattage resistor.
it is exactly you need to mention in your demo, if there are someone do not know would cause lot problem. Also, You forgot to let reader know the method measure Diode by reversing the lead of DVM, Thanks,
That depends on how much resistance the shorted component has once it goes bad. As a general rule when a diode goes bad it will have less than One ohm of resistance, so it's about the same as a piece of wire.
The voltage drop across a wire is very small, but it is never zero volts. All wires have resistance. That's why this technique works. Shorted components often have more voltage drop than a wire does.
+Grants Pass TV Repair unless i misunderstand your approach , well the caps and the diodes are all in parallel so the voltage applied was across all of them equally. So if the voltage drops are not equal there must be a voltage drop between the components which are connected with conductors. I cannot understand that this is possible unless the short is actually more short than a typical conductor .
Every component is in parallel, and by testing the voltage across each component I'm able to determine which one is shorted by observing which component has the lowest voltage reading.
+Grants Pass TV Repair two points ... I am trying to understand the physics of this . When using Mesr meter ... ok lets say you measure 1v across component one and 1.2 across component two . They are in parallel so they should have the same voltage across them .. But you are saying there is a difference . This means there must be a 0.2 voltage drop between the components because they have current running through them and ohms kirchoff voltage laws must all add to equal zero. Secondarily , your measurements are made from a common negative to the end of each component which is measuring the resistance of the tracks themselves. If you are saying there is such fine measurements you would need to measure from the leads as they come out of each component .
If you have a volt meter sensitive enough to measure very small changes as I demonstrated using the millivolt scale of my multimeter, you will see the components will not have the same voltage across them. You will also be able to see a difference using a sensitive ohmmeter.
I just watched a video by a guy called "creative Lua" and he has a cool little circuit with a LM317 a 10 turn pot and resistor, oh and a small cap. but it allow's you to turn you meter into a milliohm meter. CHECK IT OUT IF THIS INTERESTS YOU "CREATIVE LUA" IS THE CHANNEL, HE'S A GUY FROM CHINA BUT IT HAS ENGLISH SUBTITLES WITH THE CAPTIONS TURNED ON. BUT HE GOES OVER EACH STEP IN MAKING IT VERY WELL AND GIVES YOU A SCHEMATIC AND DEMO ETC!! HOPE THIS HELPS SOME OF YOU WHO LIKE THIS VIDEO LIKE I HAVE....
Hi Dave , I to enjoy finding shorts to ground, and use two different approaches depending the mood i' m in 1st is my home made milliohm meter, other more recently is a circuit I found on the web current source .25 of a watt at 3 volts, so I use that method you used, works well, to practise on I have some old tv boards, which I know have faults, so I quite moment & I try these things out, I haven't yet tried out the ESR meter, but may well Paul M0BSW uk
Complete NOOB here. Great video BUT, it seems to me like it’s like many others, in that, it assumes that you have, a general idea of where the shorted component might be. I haven’t found ANY videos, which actually explains how to determine where a short might be, or for that matter, IF what you are dealing with, is actually a short. I mean, every electronic failure isn’t ONLY a short. It could be an opened component, or a non-oscillating crystal, etc, etc. What if the device you are are trying to fix, shows no signs of damage, or burns/darkened areas on the pcb, what do you do then? You can’t just assume, that it’s a short. Sometimes, the issue can be something simple, that you just overlooked OR a super difficult one to figure out, and what/how do you start then? What/where do you start, when the device you are going to work on, shows no damaged components or pcb? That’s the kind of video, I would like to see.
@@GrantsPassTVRepair years ago we had a supervisor and the job we was on had a wire shorted out. My friend asked him how we gonna find that. HE SAID HOOK IT UP TO THAT 100AMP BREAKER. SURE ENOUGH WE FOUND IT. hahahha
seems like way more work than just to take your chances and start snipping a few anode leads until your short is gone. then a dab of solder to reconnect the innocent components
Way above my skill level but I'm always happy to meet a person that knows more than me.
I try to keep it simple so anyone can follow along, but perhaps I can do a little better.
I was just searching to see how to put a multimeter to millivolts and seen this video. I finally see how diode measured to find if they aren’t working. Video is beyond excellent.
I have a digital ESR meter but I never know I could used it in other way just like what you did in this video. Thanks for sparing some time to share us your skills sir.
What a fantastic video! Over my self-educated time spent (100's and 100's of videos and some books), what no one ever said/wrote was that in repairing electronics, it all comes down to OPENs and SHORTs; with SHORTS being the "variable" cause ... meaning that there can be a SHORT ...or... a PARTIAL SHORT that's causing the problem. Once that became apparent, troubleshooting changed to "much easier" to diagnose. I have a Zapper, built a LeakSeeker, have injected voltage, and and and. This video from 7yrs ago ... I wished I had discovered earlier. It added a very valuable approach ... inject a small voltage and then look for a voltage drop in the mA's (or maybe even uA's if you can). Brilliant. Thanks for this video.
Thank you for the comment. It's always nice to hear when someone appreciates on of my videos. We had a period where bad capacitors kept repairmen fairly busy due to a manufacture error known as the "capacitor plague", but that's not so common anymore, so other than bad eeproms and leaky parts, I suppose shorts and opens do make up the bulk of repairs. All the best.
Great video !! And tips in the comments! When I first stared out in my 20's, my boss had a Weston 7 digit ohm meter to find shorts on boards.
Boy did that work like a Champ ! 35 years later, I see this great idea using the mV meter approach !! Especially the HP concept in the comments !!
I'm so grateful and embarrased I didn't think of it ! This concept in this video should get an award !
Thanks again for making this video and bringing out further comments here with further tips !
Also, if the short is low enough resistance, you can likewise inject a voltage of much less than the voltage than the power supply and boost the current output until the shorted component heats up enough to actually feel with your finger (no using expensive freeze spray. I work repairing cable boxes for Comcast and have been able to repair a very high percentage of boxes this way. I Have used the milli ohm method as well as the ESR Meter as well as injecting voltage and tracing with the milli volt meter, too. All have their place and merit.
With Shorted chip components on a highly concentrated board with as many as 10 decoupling chip caps on a power supply line all across the PCb, it could be anywhere on the entire board. Hands down the injecting low voltage at higher current and merely feeling for heat is the most effective. I haven't had one case in hundreds of repairs where I have ever damaged the upstream or downstream components. This is mostly with buck supplies.
Thanks for this information. I would imagine a cheap thermal camera would help this process? I’ve had my eye on the “flir one pro” for a while now.
at $400 I think it would be invaluable on the electronics bench, in automotive repair, even checking the HVAC/energy leaks in your home. A friend of mine has a cheaper model… And it immediately identified the bad wheelbearings on my vehicle in broad daylight because they were warmer than everything else.
The flir one pro is pretty much the minimum priced thermal camera and resolution that one would want for electronics. Sure the $100 models work fine... but to really get down and see the smallest SMD packages and such… I think $400 is worth the extra price.
mister kluge Thanks a ton for the info! They’ve tried so many different terminal cameras… Are you referring to the “seek“ thermal camera? I know they’ve showed a few very nice thermal cameras but they are out of my price range. Closer to $1000....Where the flir one pro phone attachment is only about 400.
And with a macro lens added… Can REALLLYYYYYY see tiny parts even the smallest SMD components clear as day. and the diy macro attachment is only a few dollars. AND makes small components 10 times clearer!
Thanks for your time!
HULL GUITARS USA Did you end up getting the camera yet by chance? In a total novice with this stuff but I end up doing it often enough to make 400$ worth it, especially if it works for other applications. HVAC, home electrical, and car maintenance alone would justify it if it’s useable on a larger scale. I’d imagine it is, if it’s able to pick up the much higher resolution of electronics.
@@hullinstruments how about one of those cheap laser temperature guns? you could do the same thing with the low-volts high-current and scan the components. and those are like 30 bucks
And you don't buy a Flir because????
Great idea for locating shorts to ground; in fact you have given me an idea that I want to try out when I come across this situation again.
So simple yet so brilliant! Thanks for sharing.
Thanks much Grant you remind me of my uncle who had the 1st TV repair shop in the north Adirondacks.That was circa 1950? He was a communications guy in the Marines on Okinawa ww2
Excellent way to find shorts !! I had one in my house wiring that I found with your method. Thanks !!!
I'm a retired avionics tech. 30 years ago HP published a trick not unlike your own, using the mv on the DVM, but with no guessing. To find the short connect a current limited supply to the shorted supply rail at the spec voltage but with a safe current limit. Now connect the positive lead to the rail, and we'll use the neg probe to chase down the short. Clearly the millivoltage will grow towards the short, and if you probe past a node, the voltage will stop increasing.
I'm not to surprised. Unless you own a low ohm meter capable of 1000 divisions it's a great option.
That's how I used to find shorts until I got a $200 FLIR that connects to my phone. Now one of the first things I do is take pictures of the board temperature signature when I first power up the item. Sometimes it pinpoints the problem without any troubleshooting.
@@RickNickel hi Rick would you post a link to this?
@@RickNickel Looking at one today for the same purpose.
it kinda like the opposite of what he is doing very smart!!!
Short-Circuits (in their natural state) on PCB's have already done the damage to the equipment! I am an amateur (self-taught over 50 years). I can say that Grants Pass TV repairs have taught me that you can check out 'shorts' by the use of a DMM on the milivolt scale. I have followed the same procedure as shown in this video, and that is - to first determine WHICH CIRCUIT BOARD is faulty. Sometimes, there are five or six separate PCBs in a Home Theatre System. Narrow down the fault to just one specific PCB. Write down every step that you take! Magnification of the PCB and its' components is a must! Look for the obvious first.
I do this by powering-up the suspect PCB independently, with the same voltage / current that is rated for the particular Board. I will not reduce the voltage (or current), because a 'short' is present. Remember that the Board cannot suffer more damage!
At this point (when the suspect Board has been disconnected from ALL other Boards and Feeds), the 'short' begins to show itself........... Yes, components (even the printed copper track) will get warmer than others, because many other parts of the circuit are not being fed with their correct voltage - due to the 'short'. Have a smoke, have a coffee - but leave the suspect Board powered for 5 minutes. THEN, pinpoint every component such as diodes, capacitors, resistors, voltage regulators and transistors etc WITH A LASER BEAM. I am talking about the (very cheap) Hand Held Laser Pyrometer. The Laser Pyrometer detects the smallest amounts of heat (from or near to the shorted component), and you will definitely see results! As an amateur, I have had many hours of frustration and heartache in trying to detect a 'short'. I have no idea why all of the professionals have never mentioned this method of heat detection on You Tube. In many cases, it isn't possible to detect small amounts of heat with the human hand - from many components that have radically shrunk in size - and mass - from two or three decades ago. If I was a professional Electronics Technician, a Laser Pyrometer would be a very important part of my arsenal. Thanks to Grants Pass for a great Tutorial. Greetings from Australia.
Hi,
I know it has been years since you made this post
Could you be kind enough to provide me with how to locate any PCB power supply requirements and how to inject them for fault finding as you described in your comment above?
Thanks.
@@solseyharbal-p9j What I said was that (to help find a short-circuit) you can use a Laser Pyrometer in a few instances. In any short-circuit, there will be a component on the PCB that 'has gone to ground", and usually, the faulty component will be drawing a lot more current than it is designed to do. My suggestion of powering the faulty circuit - and leaving it turned-on, was to (hopefully) allow the temperature of the faulty component to climb - and become much warmer that normal. A Hand-Held Laser Pyrometer will measure the temperature of the component - down to a tenth of a Degree Celsius. If you do find a component that is getting warm, then you disconnect from the circuit - and test it using standard methods. Sometimes, it may be hard to differentiate a "short" with an open - circuit fault - but (usually) when there is a "short" the circuit may be drawing more current than is normal. Every component on a PCB should have an Input / Output. I hope that this helps you.
A BIG thanks for your prompt & well-detailed response.
You said '
" My suggestion of powering the faulty circuit - and leaving it turned-on, was to (hopefully) allow the temperature of the faulty component to climb - ".
Did you mean, by using an external power supply or powering up the whole circuit board to achieve the above or that?
Regards.
@@solseyharbal-p9j This depends upon how well that you know the PCB Circuit that you are powering-up. If you know the Input voltage to the PCB, and whether this is AC or DC - it helps. you could then use an external power source. If you do not have that information, then power-up by the 'normal' means. On Mains-powered equipment, I have frequently used a Variac, which brings up the mains voltage in fine increments. There are many components that will overheat, in a shorted-to-ground situation, but this of course largely depends upon the current draw. This method does not always identify a 'shorted' component on the PCB, but sometimes it does help. Sometimes, a Voltage Regulator may heat-up, and the Voltage Regulator may prove to be OK, but it is a fault further downstream - that the Voltage Regulator is feeding. There are many reasons, and (sometimes) it is a slow process to identify the faulty component(s). Hope that this helps.
Thanks for committing your valuable time to my questions, I am grateful.
Sorry for the trouble and please, for the last time, I think I failed to convey my messages or questions properly please do bear with me for the last time. This is it; I wanted to know how to identify the voltage input/requirement of an independent and the separated ( having taken it out of the main or overall board already) PCB & how to power the PCB independently using and or applying your " home theatre illustration/experience. So, in simple terms, I want to know how to power up a PCB independently and also how to identify the amount of voltage and current needed to inject and where to.
I want to be able to take a PCB out of the main board and how to inject the required voltage and current for a possible fault-finding based on your experience and the home theatre illustration above.
Regards.
This technique works very well, great on logic circuits were the 5v rail might go everywhere.
I've learnt something from you every video I've watched, thank you.
I’ve never tried testing diodes in circuit we were taught to always pull one side to open the circuit so no feedback loops. Good Information and well put together video! I’ll keep that trick on the shelf one day I may need it.
Excellent information! Thank you for sharing your knowledge with all of us! Fred
The ESR meter should be enough to find the culprit. Indeed a must have tool
Thanks for sharing your knowledge
Thank you! Gives me some more ideas. Shout out from Coos County!
I'm just getting into electronics learning Arduino and this video is helpful.
GREAT VIDEO & A GREAT LITTLE TRICK! My Teague ESI will measure down to micro-ohms, and uses a 4 lead shielded Kelvin clip lead set. That Teague is around $3000-$5000, used. The time it saves testing caps, & diodes in circuit are kind of worth it. I really love having it, and don't know how I lived without one as long as I did. I have used this method too. I liked the LCR bridge so much, I bought a spare one. It is a Chinese made no name that cost $700, but it works, despite only having 4 test frequencies, 4 test voltages & 4 test current. The Teague has 100s. I fixed up a Samsung plasma TV only to find it puts out excessive RF interference into the mains, making my amateur radio station noisy. Plasma TVs are notorious for backfeeding RF noise into the power lines.
Thank you for a good video!
Thank you. Very helpful information.
You need to know something about the trace geometry to accurately pinpoint the short using this method. You need to measure the voltage drops across the traces.
I start by connecting the negative lead of the DMM (mV mode) to the point where the current source's negative terminal connects to the PCB. Then begin probing further from negative connection point until the voltage stops increasing. As long as the voltage continues to increase, you are following the flow of current. As soon as it stops increasing and levels off, you've passed the short. If you have a layout viewer, it really helps.
Using this technique with boards that have power planes is more difficult. You'll need a high precision DMM to measure micro-volts of change on top of the millivolt voltage that is actually across the shorted component. You may need 6-digits of precision to do this. The relative (delta) button won't help because the meter will use the appropriate scale for the total voltage ("trace voltage drop" + "shorted component voltage drop"). You are only interested in the trace voltage drop.
I suggest using a good cad viewer that allows you to highlight nets and has coordinates so you can calculate distance. I've used this technique to get me within about 1/2 inch of a shorted cap between Vcc and Gnd on boards with hundreds of bypass caps on them. I also use thermal LCD paper and cold spray to try to locate the shorted part thermally.
In India, we mostly use rosin paste and 3.3v with few good range of amps (current) and volts depends to the supply line or supply track. And we easily find the shorting component. There are many ways to locate the shorting component and those are effective too.
Hi Dave
Another great Video. Thank you for taking the time to show us your troubleshooting tricks. Keep up the great work you are doing.
Cheers
Willy
A thermal camera would have being really nice
This technique seems similar to 4-wire resistance measurement. Very ingenious application for repair!
Big thanks for these very powerfull techniques, voltage drop is really revealing
I'm glad you found this technique helpful. Thanks for the comment.
Excellent Dave.
another excellent video. although in my experience finding a short to ground is a lot tougher than you have shown especially if you have a bunch of smt noise caps or the short is between layers.
Roger Kerr I agree. Finding shorted diodes and large transistors is fairly simple in comparison to what you describe.
Thank you i have been trying to do a similar check with sm caps in parallel☺
Very good teacher.
MrMac5150 Thanks.
send some more of your skills this way.
this is nice. thank you. I been back to watch this video several time. I also have the toneohm, which, I am in the process of making my own leads since its leads are crazy expensive, I am yet to learn how to use it though.. but I have found using a good thermal camera, though expensive but is a very effecting and fast way in finding shorts. I would call thermal camera, short finder for dummies.
Thanks for taking the time and effort. well explained.
Good info. Thank you.
Thanks very much for sharing. I too use my ESR meter for finding shorts but you've intrigued me with the short sniffer that I saw it costs quite an insane amount of money. 10 minutes later, I have one up and working just great, it's just a prototype of course but more or less I made myself and idea of what values of components I have to use. If you need any help, just ask. Cheers :)
Tap on a clip to paste it in the text box.
nice tipoff about the audio frequency of switching power supplies
Thanx for the video very useful & educational !!! Keep them rolling my friend
Well done. I have not used this technique, but you can bet that I will.
Your really good at explaining
Nice job. I'm working on a small board with a short somewhere. I'm going to apply a small voltage (3 D batteries, 4.5v) with a small current limiting resistor and try to get closest to the short with digital voltmeter readings OR allow more current and feel for a hot component.
very good most helpfull tip haow can you check for a winding short in a transformer do you have to use a micro ohm meter and know what a good one would read?
I do have a micro ohm meter, but when I test the primary side of a transformer I often use the my blue ring coil tester. Here is video on how they work. th-cam.com/video/Ky2T1-n_Fks/w-d-xo.html
Finally.....thank you SIr
this is a great way to find bad connections on car battery leads
Usually to find shorts of that kind, i usually plug a lab supply across the shorted rail and inject some power and look for the hot parts.
***** I've used the same technique, but sometimes it takes quite a bit of current to get the component to warm up.
Thanks Dave. I appreciate the video.
thanks for this, this is what i needed to see!
You can use a Seek Pro thermal imaging camera to see what heats up the most to find it fast too!
91% IPA (isopropynol aka isopropyl alcohol)pour on suspect components then inject voltage and you will know what is shorted by how quickly it evaporates. Much cheaper than thermal cameras
@@Heathmcdonald That's the way to go!
ESR meter can also read very small value resistors.
Thank you so much. unfortunately, my bench power supply doesn't control current that accurately so I created a simple constant current supply circuit that I use now for this method.
Great video, thanks! There's a potential (little) goldmine out there if you can get the "throwaways" before the "scrappers". And if they are repairable. I bet most are.
I like the ones with broken screens, if they come on ther usually some fairly good boards inside.Sometimes it's deceiving.
Very very helpful , thank u , hope u get time to make some more videos soon , I enjoy watching them
This was really helpfull, thank you.
Yes it helped, Thank you so much
I'm not sure I understand what you're looking for... Every measure you did had different values for different diodes. You KNOW one of the diodes is bad in this case, but the only indication you have for which one it is would be the one with the lowest value in whatever measurement you're doing.
But if you don't know if it's a diode or a capacitor (or any other component, for that matter) that is the culprit, how would this help you? You haven't really located the short, because to even use the technique, you must know which component type you're looking for. And even then, it only works if all of the components of that type in the circuit has the same value. And even then, you can get "false positives" because of the natural difference in the readings.
This procedure is designed to help you find a shorted component where there are multiple components which share the same power supply output. it's not going to tell you if a diode, capacitor, IC, or transistor is open, but if one of these components is shorted such as a diode it will have the lowest voltage drop of all the components you test. I hope this helps.
Very useful. Thank you.
Very helpful video! Thank you!
I fixed my MacBook Air with this method. It had shorted component somewhere on the main power rail to ground. Supposedly, capacitor. But which one of many (about 100)?
I put about 0.5V 1A to the board and then started to measure all capacitors to find one with the least voltage on it (because it will be the shorted one).
And I found it! With simple cheap multimeter and power supply.
I think this is the most professional method to isolate the shorted component. I want to know about if this method can be applied to computer boards. If possible, can u make some video on that?
Great way to test for shorted components BUT that's IF you have more than one of the same component [with which to compare it with - like three similar values diodes]. But how can this work, when the components are of different values to each other AND altogether different components? Ex: a transistor, a cap [tear shaped - tantalum], an electrolytic cap, few resistors and maybe a diode. What can you possibly achieve test-wise with this method [ESR meter]? You would never be able to find the shorted component. But I have so much more to learn about electronics [I'm a complete NOOB in this field] so, PLEASE correct me if I'm wrong - I truly am trying to learn. Your videos have been a great source of education for me. Thank you kindly.
hi, is there a difference between a bad diode and a shortened diode when checked with a meter what i am asking would a shortened diode measure as bad with a meter ? thank you
I don't quite understand your question, but I think you meant to say shorted diode rather than shortened diode. ;-). When the short out they generally become like a piece of wire with almost no measurable resistance. Less than 1 ohm.
how value voltage and current to charge? for not damage the other component
Could you also use nS to measure conductance and then convert it to ohms? For small resistances. The fluke 87v has nS but is kinda hidden.
I don't understand your question.
Never mind. I was thinking you could use Nano Siemens which can be used to measure very hi resistance. In this case your measuring very low resistance. My fault. Thanks
excellent, thank you for sharing your hard earned knowledge, much respect!
Got that trick from (How to diagnose and Fix everything electronic) by Michael Jay Geier.
Thank you , great tip!
Thanks! helped me find the needle in a haystack.. bad SMT cap
Gustav Kirchhoff would turn in his grave if he saw this video......
Those components are in parallel , the voltage drop across the components will be identical as you are measuring rail to rail. They will be passing different currents depending on their resistance but the voltage drop across the rails will be the same no matter where you measure.
The more sensitive you make your meter readings, the more you will think that a few millivolts here or there mean something when they actually dont..
There is a reason why components in parallel need to be unsoldered to check, and this is a good lesson in why.
omgffsification Technically speaking the only voltage drop you really see in this example is from the shorted
diode. The other diodes direction are not in the conduct mode, and capacitors do not pass DC. I should have used slightly different words to describe this example.
Grants Pass TV Repair Sure but how is this test telling you which diode is shorted?
When diodes go bad they generally short out and their resistance goes down as the diode junctions become fused together. This test is showing me which diode has the lowest resistance reading within a few thousandths of an ohm.
There have been time in the past where I actually used the most simple and cheapest piece of test equipment I have. With a current limited supply and a little bit of current I used my finger to find who's getting hot... ;-)
We have a variety of ways to accomplish the same end result when looking for shorts to ground. Sometimes I use a lazier temperature probe, or I freeze spray the whole board until it turns white, and then watch to see which components are the fist to defrost. Louis Rossman made a video where he poured alcohol on his circuit board, and then watched to see which area of the board evaporated first.
LoL that is kinda funny, I thought you were gonna say where the alcohol starts sizzling... Yeah we are a creative group sometimes. More then most other groups....
whats the type of the "paper" that connects resistors
you use for simulation? thank you!
Adhesive copper tape. Available everywhere, here is a link to one site that sells it, there are other sites, or outlets in your country as well. www.sparkfun.com/products/10561
super video , congratulations
very informative video
Thank You very very much sir this works excellently,
Have any idea how I can force yt to put up your newest videos? I go out of town and upon returning yt seems to "retire" subscriptions to the back burner. I imagine just finding and watching a few is the only way.
madisonelectronic I put an index to all my youtube videos at www.tvrepairinfo.com/
Hey, you can just supply this troubled PCB not with ordinary high input voltage but with low voltage and high current capability power supply. And just use your fingertip to locate a shorted component(s) by its temperature. )) Any advanced multimeter needed, but ATC 300W power supply in tact is strongly recommended to have in your workbench.
can a diode be tested when still atteched to the board?
+VINCENT ONGALA Most of the time you can test diodes which are in circuit, but sometimes you must remove them to know if they are shorted due to the surrounding components on the board . Anytime you remove a diode which appears to be shorted it's always a good idea to test them out of circuit to make sure your test results were not effected by surrounding components. Most of the time a shorted diode will have less than 1 ohm of resistance, so when I get a bad reading using the diode check function of my multimeter I switch my meter over to the ohms function so I can get more information about the nature of the short in terms of how much resistance the diode appears to have in circuit. If the ohms reading is 10 ohms or more I generally assume the diode is probably okay,
but when in doubt pull them out to double test.
Can you go more into Filters Circuits?
That's a broad question. What kind of filter circuit?
thank you nicely explained.
can we use this method to find a short on a Laptop mother board?
Yes. If you know where to test such as a positive power rail that should never have an extremely low resistance reading to ground. If you don't know where to test on the circuit board you can check for shorts across your capacitors. If you get an extremely low resistance reading it means you have a shorted capacitor or something on the circuit in parallel with the capacitor may be shorted.
Should I connect the VDC power to a short circuit as your demo???
+Hiem Ngo I'm not sure I understand your question.
I am wondered when looking at your demo when you turn ON DC power supply and connected to a short circuit that you made it by your own. I think it would feedback and blow power supply if you leave it for a certain time. THX,
Yes it could be a problem if your asking the power supply to deliver more amps than it can handle. My power supply can deliver up to 3 amps with out there being a problem to my power supply. If your power supply can't handle what ever current a short circuit produces, you can add a resistor in series with the device your attempting to repair. You resistor will probably get hot if your device has a short so you may need a high wattage resistor.
it is exactly you need to mention in your demo, if there are someone do not know would cause lot problem. Also, You forgot to let reader know the method measure Diode by reversing the lead of DVM,
Thanks,
The noise is caused by pulse skipping. Even a minimum pulse width PWM will be inaudible because the switching frequency doesn’t change.
NICE . ThanX !!!
cheer's another couple of top tip's
Wouldn't the voltage drop across a shorted component be zero volts? I was told it acts like a wire.
That depends on how much resistance the shorted component has once it goes bad. As a general rule when a diode goes bad it will have less than One ohm of resistance, so it's about the same as a piece of wire.
The voltage drop across a wire is very small, but it is never zero volts. All wires have resistance. That's why this technique works. Shorted components often have more voltage drop than a wire does.
I am trying to understand how parallels can have different voltage drops . I assume there must be a voltage drop along the tracks joining them ?
I don't understand your question.
+Grants Pass TV Repair unless i misunderstand your approach , well the caps and the diodes are all in parallel so the voltage applied was across all of them equally. So if the voltage drops are not equal there must be a voltage drop between the components which are connected with conductors. I cannot understand that this is possible unless the short is actually more short than a typical conductor .
Every component is in parallel, and by testing the voltage across each component I'm able to determine which one is shorted by observing which component has the lowest voltage reading.
+Grants Pass TV Repair two points ... I am trying to understand the physics of this . When using Mesr meter ... ok lets say you measure 1v across component one and 1.2 across component two . They are in parallel so they should have the same voltage across them .. But you are saying there is a difference . This means there must be a 0.2 voltage drop between the components because they have current running through them and ohms kirchoff voltage laws must all add to equal zero. Secondarily , your measurements are made from a common negative to the end of each component which is measuring the resistance of the tracks themselves. If you are saying there is such fine measurements you would need to measure from the leads as they come out of each component .
If you have a volt meter sensitive enough to measure very small changes as I demonstrated using the millivolt scale of my multimeter, you will see the components will not have the same voltage across them. You will also be able to see a difference using a sensitive ohmmeter.
Great Video .
Thanks
The $1 diy diode tester is the bees knees
Great Video
Mitsubishi #WS-5561 Turns off then can turn on again may work for ??? time. Then turn off again. No green blinking.
Awesome vid.
I just watched a video by a guy called "creative Lua" and he has a cool little circuit with a LM317 a 10 turn pot and resistor, oh and a small cap. but it allow's you to turn you meter into a milliohm meter. CHECK IT OUT IF THIS INTERESTS YOU "CREATIVE LUA" IS THE CHANNEL, HE'S A GUY FROM CHINA BUT IT HAS ENGLISH SUBTITLES WITH THE CAPTIONS TURNED ON. BUT HE GOES OVER EACH STEP IN MAKING IT VERY WELL AND GIVES YOU A SCHEMATIC AND DEMO ETC!!
HOPE THIS HELPS SOME OF YOU WHO LIKE THIS VIDEO LIKE I HAVE....
Hi Dave , I to enjoy finding shorts to ground, and use two different approaches depending the mood i' m in 1st is my home made milliohm meter, other more recently is a circuit I found on the web current source .25 of a watt at 3 volts, so I use that method you used, works well, to practise on I have some old tv boards, which I know have faults, so I quite moment & I try these things out, I haven't yet tried out the ESR meter, but may well
Paul M0BSW uk
Thanks for the info. I miss the days when searching for shorts to ground was a regular necessity.
great video. Thanks
very informative , thank you sir
Another great education. Thanks!
11:03, *smaller* voltage drop. I know you knew that... (c:
Thank you very much
Complete NOOB here. Great video BUT, it seems to me like it’s like many others, in that, it assumes that you have, a general idea of where the shorted component might be. I haven’t found ANY videos, which actually explains how to determine where a short might be, or for that matter, IF what you are dealing with, is actually a short. I mean, every electronic failure isn’t ONLY a short. It could be an opened component, or a non-oscillating crystal, etc, etc. What if the device you are are trying to fix, shows no signs of damage, or burns/darkened areas on the pcb, what do you do then? You can’t just assume, that it’s a short. Sometimes, the issue can be something simple, that you just overlooked OR a super difficult one to figure out, and what/how do you start then? What/where do you start, when the device you are going to work on, shows no damaged components or pcb? That’s the kind of video, I would like to see.
You may find this video helpful. th-cam.com/video/qotB1xxQols/w-d-xo.html
U could start applying more current and use a thermal image camera for hot spot
That's one of many ways to find a short.
@@GrantsPassTVRepair years ago we had a supervisor and the job we was on had a wire shorted out. My friend asked him how we gonna find that. HE SAID HOOK IT UP TO THAT 100AMP BREAKER. SURE ENOUGH WE FOUND IT. hahahha
seems like way more work than just to take your chances and start snipping a few anode leads until your short is gone. then a dab of solder to reconnect the innocent components
Clipping leads or un-soldering multiple diodes sounds far more labor intensive than a few quick probes with a low ohm meter,
Good video. Thanks!.