Everything You Should Know About Voltage Injection - LFC

[@Adamant_IT]

One more thing of note, while this video covers text-book cases, keep in mind that there are always many edge-cases. Some more modern GPUs can read less than 1ohm at vcore, so great care should be taken to make sure a less than 1ohm short on the main rail isn't the same as the less than 1ohm of resistance through GPU vcore. Likewise, you can also have partial shorts, where a capacitor or even a fuse can be shorted, but still offer some resistance.

[@vlatkosurlan545]

Fuse is just a calibrated wire. It's always shorted. It can burn up partially though, and offer some ohms where there should be none.

[@Mikie1959]

Graham you would be one hell of a tech teacher you explain everything so plain and simple so everybody understands what you are saying .

[@Bartosh.S]

He IS one hell of a tech teacher.

[@DMP2923]

My thought exactly. What do you think he is doing...teaching

[@Mikie1959]

@@DMP2923 he is basically teaching us on youtue but he could be a great professor at a tech college he explains everything in simple terms anybody could understand .

[@mrBDeye]

He is one “heaven” of a tech teacher.

[@Akatsuki-Wii]

@@mrBDeye he is on Earth of a tech professor

[@michaelmitchell8218]

Just watched this video, I do electronics and repair many laptops and I see so many videos of rubbish fixing laptops,PS5,Xbox,Tv, etc and I got to say this is one of the first videos I seen where this guy knows what he is doing and talking about. I give this a full thumbs up and should be more of this. Be careful people because there is so much rubbish on you tube and if you know nothing about electronics then don’t even try to fix anything, go on a electronics course. I been fixing electronics for over 30years and there is always new things to learn. Anyway love your video and fantastic work my friend.

[@Adamant_IT]

A lot of KZbinrs including myself kinda learned as they went, making videos while they were figuring stuff out. I'm trying to correct my old works now. This video and other ones I have planned I'm running past a couple of veterans on the repair scene and saying "You have the knowledge, I have the audience - is this accurate? is this portraying the information that you guys want people to be learning?"

[@carloazuararuiz1069]

@@Adamant_IT 2 veterans of a thousand battles as technical support behind you? It had taken a long time young Graham... excellent decision. That will increase your subscribers. All the best.

[@Ballyanden1]

Thanks Graham, there are a few you tubers that go strait to voltage injection - they probably get it wrong a few times and call it a no fix and say better than factory when they have actually broken a fixable device 😀 I really like this logical approach. I prefer to take my time and get it right than rush in to save time. Many thanks for the videos 👍

[@fredrickrari9338]

I think I know who you are talking about😂 its never a fun thing to see an item being dismissed because its not worth the time or voltage injection wasnot done correctly

[@khlua4590]

the bridge

[@rickpontificates3406]

It is good to use a current limited supply, but if you stay under the rated voltage of a circuit, YOU WILL NOT fry good components because if they're not shorted, they'll only draw what they need

[@vasyltokar4062]

This is gold for who is new in fixing boards. Cheers mate

[@NerdThingsAndMore]

This is the best video explanation I have found on KZbin Thank you!

[@sharymens8187]

Thank you so much for your time and effort in making these videos!

[@mj1henry1]

Working on a faulty board now, learning voltage reading, voltage injection and fault finding and i learn so much by failing! Funny thing is... I watched this video before.. But watching it now makes me realize how much I didn't understand before. Thanks for what you do!

[@Ghost572]

Those old methods do still hold their wieght in the sense that if your thermal camera ever broke you have backup options. Also I saw on northridge fixes channel he was trying to sell these voltage injectors but I was wondering what the hell is he going on about, he said he broke a channel on his power supply (not sure how someone that experienced didn't use a current limit) and that somehow a power supply isn't designed for voltage injection (like what??). That's exactly what a power supply does, it supplies (or injects) voltage,current and energy into a board. It's like every video he's trying to sell you something or even better guilt trip you into buying his stuff.

[@darrenmurphy6251]

Respect for showing an ambiguous board most you tubers specially select the clear easy faults and create an artificial idea that what we do is easy and decisive

[@nivanthafernando5189]

Bro, this is one of the great demonstration and explanation by anyone can do their best. I respect your afford taking to share your Knowlege with learners. Hopefully you will be blessed to bring more videos like this in future.

[@m-elokkichawki9694]

i had the same idea but still a very usefull channel

[@jameysummers1577]

This is the ONLY component diagnosing video that clearly explains what a short is and how to find one properly on a laptop motherboard. I'm not sure if you knew that, but this is a great video!

[@LarixusSnydes]

I like my DMM that also *shows* the resistance measured when in continuity mode, so, if I hear a beep, I can just look at the screen and find the resistance measured and inspect closer *if* it's a dead short or not. Props for not jump-cutting to the moment that it eventually powers up. That helps keep things realistic.

[@jonathaningram4672]

Also ALWAYS cross the probes and set voltage/amps before linking up to add power injection as some bench power supplies spike before stabilizing to set voltage

[@jstro-hobbytech]

Especially if using an smps. It drives me nuts that you have to intentionally put so much strain on your bench supply because they're too cheap to add the ability to current limit another way. My wife got me a 3 output siglent for Xmas (which blew my mind) but it's spoiled me for setting current limit at the touch of a button. I have a longwei and kaiweets pair that are virtually identical except for paint color. I paid a fortune for the longwei and now it's less than half price. Kaiweets sent me the other for free out of the blue with an email (I signed up on their site because of discounts as I've given their dmms away as gifts) then demanded a review. Haha sure I told them. I was gonna start a channel this month for a local club I'm involved in but decided not to. But they sent this over a year ago. Weird ehh. I heard they did it to others as well. Someone gave me their ht208d clamp meter as a gift and it's one of my favorite meters and probably the most expensive one they sell. I have a fluke clamp that was twice as expensive with half the features and zero input protection on the probes. I've since donated the fluke as I believe they are not worth the money with brands like brymen making more feature rich meters at half the price. Sorry for windbagging. Europeans are spoiled for choice when it comes to brymen. I had to order mine from Germany to Canada from welectron on ebay. I'll never buy a thing from welectron again. Their service is horrible. Stereotypical Germans as described by marco reps lol. Wouldn't except a promo code I had and wouldn't honor the warranty after 1 month.

[@Dutch-linux]

best to use is a low ohm's meter that has a range from 2 ohm to 0 ohms .. they are expensive but super accurate for short finding

[@redmist4963]

Just a multimeter with 1 mohm resolution would do the trick. They are mostly found in bench multimeters but you could also use 10 mohm res.

[@harryf1ashman]

can you recommend a particular model

[@priekabos22]

totally respect you!!! so clear and strait explained, probably the only video ever who made so well! you are legend man

[@hamradioop5777]

Thank you Graham, a thoroughly enjoyable and educational experience. I've watched dozens of professional repair videos and yours has been the only one to provide very necessary learnings,😇 before I blow-up something by being too gung-ho.

[@luiscornejo9775]

Before voltage injection, and if you have access to schematics like you did, you should also check whatever rail is shorted and what IC provides the power for that rail. Sometimes a rail is only supposed to be delivering for ex. 500mA. You can check this by the IC datasheet and the max current rating. If the issue is the driver IC providing power, there's no need to allow your power supply to supply 3A of current. Pulling 2-3A risks damaging downstream components that were fine to begin with

[@Dutch-linux]

Very educative video you should make more like these really liked this one thanks

[@Adamant_IT]

Yup, I'm planning on doing a brand new Board Repair Basics series to replace my old tutorial videos that aren't super relevant to modern systems, and from a time where I had significantly less experience.

[@abdulazimpatel8467]

Please do.

[@carloazuararuiz1069]

@@Adamant_IT I would love for you to start with Dell (your favorite brand and mine too). All the best.

[@toms4123]

What a great teacher, focussed, well structured and articulate. Thank you for this video

[@joseph_donovan]

Love your methodical and analytical approach to diagnosing, troubleshooting and fixing a short circuit. This video is packed with nuggets of good and safe practice. Thank you!

[@mor1249-n8d]

Thanks Graham, very good video. In the 70s we called it the Indian method when troubleshooting radio and television. We checked where the smoke was coming from. 😉 Can't recommend it today. A bit too expensive. Thanks for all the videos you share. 🙂

[@robertjung8929]

actually all electronics is running on smoke. when the smoke escapes it stops working :)

[@thomaskyalo7753]

I was waiting for this coz power injection is a very sensitive area especially on the WHERE to push the amps. Thank you Graham

[@jonathaningram4672]

Top marks, must also know resistance from leads on multi meter before even starting. I understand low resistance and will beep but will not show dead short. Best explanation on this subject.

[@peterlorne7077]

Very good video. Thank you for not talking so fast! It means that those of us who are not very good at English can follow you. Thank you!!

[@paulconnell5399]

The self critical nature of some of the preamble is awesome. Great teaching style. Love it.

[@ImranOO7]

As always, great content and really enjoy and look forward to your videos. Keep up the good work and my deepest regards

[@saydmarschany8321]

I admire your work, like the way you take your time in figuring out the problem and solution to whatever you are faced with. I am a hobby-ist and trying to learn as much as I can, and find your videos very educational. Thank you.

[@fabiofabtube]

Very, very, I say again: very good explanation of this particular issue! Not to mention the fun in watching the video and the pleasure of the accent, understandable to non native english people. Great teaching style! Thanks sir

[@clarovillarta7983]

Awesome!Thank you graham for explaining the gray areas on volatage injection in finding short caps (dead short) Thanks

[@usmanwiyfengla8019]

best Tutorial ever. Thank you Master. You make life easy and better for us in Cameroon and Africa atlarge with expirience and almost no teacher to help young people like us grow in this field. and grace and wisdom to all what you do

[@tcrawford314]

This video was very insightful. It has given me the confidence to troubleshoot a dead laptop I have been avoiding. Thanks!!

[@Alvin853]

20:08 you absolutely can inject voltage on a shorted VRM MOSFET, all you need to do is put your negative probe on one of the inductors of the power rail, not on ground, so the CPU is not part of the circuit you're checking for a short.

[@robertjung8929]

can you elaborate on that ? 😁 the CPU is part of the circuit no matter what you do... GND pins of the CPU are connected to groundplane and the Vcore/gt/aux rails are connected to the corresponding inductors.. no matter where you inject, the CPU is part of the circuit... to safely inject you need to go as low as 0.8V and check with thermal camera what gets slightly warmer.

[@Alvin853]

@@robertjung8929 Look at the Diagram at 3:10 in the video, but assume the short isn't one of the capacitors, but the VRM MOSFET labeled VRM right above the CPU. If you inject voltage on the main power rail, and have the negative probe on ground, then current will flow positive probe -> main power rail -> VRM -> CPU -> ground -> negative probe. If you instead put the negative probe on one of the inductors (which is between the VRM and the CPU in this diagram) then the current will flow positive probe -> main power rail -> VRM -> negative probe, and the CPU is not part of the circuit to and from the bench PSU. Yes the CPU is still on the board, but there shouldn't be any power except the bench PSU.

[@dreamcat4]

@@Alvin853 understood perfectly well my friend.... a pro tip indeed, especially to go around all the vrms first of all... the other comment also to stick to injecting 0.7 or 0.8v. very good man 👍

[@robertjung8929]

@@Alvin853 ok i see your point.. but you effectively checking the path between B+ to the inductor only, and that's basically the high side mosfet and nothing else .. this way you will not find the short if the low side mosfet or one of the output capacitors are shorted. and actually to check the high side mosfet only for short, it's perfectly fine to check with multimeter, no need to inject current. the point of current injection is to "test" many components at once. as i mentioned earlier , the best approach is to inject current with compliance voltage set to the max supply voltage of the CPU/GPU. e.g. 0.8V is safe for everything (even 1.0V is safe).

[@Alvin853]

@@robertjung8929 If the low side MOSFET or any output capacitors are shorted, then you don't have a short on the main power rail to begin with, and you shouldn't be injecting power into the main power rail at all. And since there are usually multiple high side MOSFETs, you can't figure out which one is bad with a multimeter, so you need to inject power to see which one gets hot, that's the bad one.

[@hinny2005]

I did my first voltage injection yesterday. I think I was injecting directly into a ground plane at one point 😂 I started at 1v made sure the GPU or cpu didn’t get hot. Then cranked into up not sure what got a bit carried away and found a capacitor at 200c. Surprisingly found the short and old Alienware laptop fixed! So satisfying 😂

[@dinterreynolds763]

Thanks

[@wartlme]

Reading in Diode mode is helpful and sometimes gives you more info, especially if you check junctions.

[@ctrea91]

this is my favorite channel from now own.. very specific. good job for that

[@bienhelado204]

I love your graphics and appreciate how much time it takes to include them in the video. You have a way of teaching that captures my full attention.

[@frankmormando3917]

Great great explanation, seriously! Tech teacher quality! I've been watching many electronic repair videos in the past 6 months and I gained a bunch of valuable information and I have a lot of electronics knowledge myself. Thank you

[@chrisamon5762]

Thanks for explaining the short to ground term!

[@sipansibabdreddknot5179]

i find it easy to listen to you and quite explanatory on the things that we should pay attention to so all my lingering question and maybe in the future repair i came backup with the reasoning behind to fix laptops faults or any other electronics, thanks alot!

[@michelk1445]

Wow is this a really great video. Now i understand what a short to ground is en when it is right to insert voltage. Chapeaux 👍

[@gabrieln5357]

Very well explained, m8! You certainly have the quality of a teacher. You should definitely pursue this career my friend! 10 stars from me.

[@robertisaacs5122]

Great Video and good explanations. Thanks for taking the time to make this.

[@keiths8700]

Another great video Graham! Thanks for the 10 out of 10 explanation and awesome video work!!

[@colinreece3452]

Thank you Graham, as a complete novic one of my main problems is knowing ho to set the multimeter to what? I'm being honest, not got a clue so I leave well alone. This made me think to what you said earlier setting it wrong could lead to a big mistake. When I've watched other say I set the meter to XXX mode they should show it on the multimeter where the dial is pointing to.

[@Adamant_IT]

I was going to move to an on-screen multimeter, but I decided to go with a camera-pointing-at-meter setup for this exact reason. I'm still fine tuning the camera angle, but the objective is for people to be able to see that I'm using an ordinary cheap meter, and where the dial is set at any given time.

[@cfq.tufanuf7601]

Great video Graham!! Well needed as lots of people interested in voltage injection. Thanks

[@HenriqueFerreira-lj9nj]

Thanks for sharing your knowledge... Greatings from Portugal 🇵🇹 🌟

[@RayMondElec]

We need more teachers like you. Keep up the video's. They are greatly appreciated. Thank you

[@Synthmonkey]

I work with sigma in-circuit test machines daily testing many different pcbs (which I know would be a very expensive way of doing what you do) but you have explained this perfectly. Nicely done and a really informative.

[@Andrea-cz6go]

Semplicemente MAGNIFICO! Hai fatto un video di cui avevo bisogno e che in Italia non fanno perché pensano che tutti sappiano.Bravo bravo bravo!

[@nicolaslacoste9367]

Thanks a lot for your knowledge sharing. A lot of fix videos don't explain how to do a diagnostic but only to fix a common issue on a device. Thanks a lot for all yours videos. Best regards, Nicolas

[@NotThatGuyJD]

Finally learning what voltage injection's definition is.

[@retrocomputinggrotto]

Very well explained. Between you and Sorin (if you know, you know) I'm going to learn lots from you.

[@DarrenSteele-mx3ks]

Hey, it's great to see your videos again I Thought you were gone! You were LFC? "let's fix computers"? Well, it's great to see you in action again and I will subscribe now. Cheers!

[@jstro-hobbytech]

Hey man. Great video. Best explanation I've seen yet. I am a hobbyist but have an absurdly ostentatious repair setup. I am humble enough not to do this until I learned. I'm getting a thermal cam from a content creator friend who doesn't have android otherwise I'd never pay for one. I can limit on one of my linear supplies to microamps and I'm wondering if it has to be such a high amperage you're using? I'm more into the theory side of things but I like to buy broken electronics that's would otherwise go to landfill and give them away. Especially old game systems. I know you're only putting in 3 watts at most but 3 amps makes me weary haha. I trust your expertise however.

[@gogee8510]

Great clear commentary on voltage injection. Love the video.

[@Jay-uw2eb]

Great video, for those of us who actually understand the basics this was very well explained to get to the next steps 👍

[@Retroornew]

Great Video and perfect explanantion from start to finish including the tools and equipment that you use Graham professional as always.

[@MasterJediSean]

Brilliant video my friend! I have watched this a couple times now and will review when needed. As you clearly explain the particulars. Thank you so much for this helpful. I like your teaching methods. More troubleshooting! Love it! Cheers Mate! from a friend in Surrey BC Canada.

[@coopydan9906]

man I am so thankful for your superb advice. My Alienware 17 experienced this failure and I was able find the problem myself thanks to you. Love your work. Thankyou so much 🙏

[@cristianleon7533]

Just subscribed. I’ve been in this field for a couple years and I’m just getting into more advanced motherboard repair than basic soldering and this will probably help me out a lot. Thank you so much, looking forward to watching more of your videos.

[@woollysoxx]

Super video! Great information, I always learn from your tutorials.

[@HeavyLightRepairs]

This video has been exactly what I was looking for. Thank you very much! Been binging your videos recently :D

[@Fox-BZH]

Quelle excellente explication ! Un grand merci à toi ! Bisou de la France !

[@tolgaaydin1981]

Thank you very much for sharing these tutorials and detailed repair videos. I am patiently waiting for your videos.

[@carlosgarciaoropeza5480]

(24:16 - 25:10) That's what I get for rejoicing in advance: I thought you had fixed the previous MoBo (LFC348) and I even watched each video twice to convince myself😟😔. However, thank you very much for sharing your knowledge, your experience and above all for your effort and mainly your time invested in the elaboration of this type of content exposed in a simple, clear and understandable way for many (novices and advanced) that reinforces our knowledge about this important topic. A sincere, affectionate greeting from Mexico.

[@teribleTube]

This is the best explanation ever.Thank you!I'm going to learn lots from you Graham.God Bless you man.

[@ecurepair]

Nice and well described! Your video's have gotten a lot better.

[@zdkama]

Holy cow, what an excellent video. Thank you for your attention to detail, I learned an absolute ton. Subbed.

[@JohnSmith-yw3jr]

As a self taught repair person - I truly appreciate the moments when the job doesn't go perfectly. It makes me feel better about my own repair experiences. Like I'm not alone... 😊

[@Adamant_IT]

Definitely! What you didn't see in this video was the literal 15mins of me turning the board and looking everywhere because I thought the hot spot was another reflection, since it was so subtle this time around. KZbin videos are always the highlights, not the whole story, mostly because the whole story is very long and dry to watch.

[@saltcityrepairs5121]

This is definetely one of my favorite video. Very well explained. Very useful! Thank you for sharing. Exactly Correct as you mentioned. ❤

[@MrLennymon]

Thank you, I was not even trying to learn anything tonight. I learned a lot which will help if i ever get to the point or desperate enough or I get that new thermo camera and a screwdriver . You made a nice video, I watched it straight through enjoyed every minute

[@MeitsMSX]

Great video. Good to see you demonstrate the difference between mainrail and VRM resistances. If you ever get fed up with your thermal cam, try the Guide IR PC210 with a macro lens. It doesn't just see a faint glow of heath in a certain area, it sees the component being hot. And that for a fraction of the cost of a Flir.

[@sharymens8187]

At 40 min, if you had used hot air instead of the soldering iron, and there was an IC so nearby that you couldn't put aluminum or Kapton tape between it to protect it from heat, could it have become a problem such that the IC had to be reballed?

[@johnd942]

Well done! A very informative presentation. I learned a few things. Thanks!

[@jameysummers1577]

Again....This is the ONLY video that explains this. Everyother video just shows someone injecting voltage, something glows, they replace it and look like a God.

[@irmadion4904]

Very well explained and incredibly helpful. Your are one the best teacher, I have seen ever....

[@electronicrepairservice2020]

An excellent explanation/lesson. 👍Thank you for taking the time to make this informative video!

[@carlojoselitochua2954]

Done watching, thank you very much for the detailed troubleshooting procedure. I have learned significantly more troubleshooting & repair lessons in this tutorial video and to your other repair videos as well compared to my ENTIRE 4 YEARS OF COLLEGE EDUCATION. I hope you will soon have a mini-series for Schematic & Boardview-free Voltage/Power Rail Tracing[12V/18-20V Main Voltage Rail, 5V, 3.3V, CPU/GPU Core Voltage Rail, DRAM Voltage Rail, IGPU Voltage Rail, System Agent/Northbridge Voltage Rail, PCH Voltage Rail, BIOS Voltage Rail, Battery Power Rail], Proper method of testing/checking of potentially faulty MOSFETs & ICs/Controller Chips, CPU/GPU/PCH Reballing and BIOS Bin File Editing.

[@tonymamwell6333]

Awesome video. Clearly explained

[@rongray8934]

Thanks for sharing all your knowledge. Great video.

[@transformateur9969]

Thank you so much, I love your videos!

[@cazi7244]

Great video and very well explained! Thank you!

[@lizzmk]

This is what I’ve been looking for how, when and where to inject 👍 you’ve explain it clearly

[@manuelvillanueva3753]

Amazing... Cheers! Good and straight forward explanation...

[@gvenagas]

If I had to watch only one video on electronics repair, this would be it!!! ❤❤❤

[@mehmetcakoglu866]

Excellent lesson! Thank you and cheers from Turkey :)

[@DarkWhite1]

Thankyou, finally sombody explains it properly step-by-step.

[@gvenagas]

Excellent explanation! Thank you for sharing your experience and knowledge!

[@TechRIP]

One of the best educational video's I have ever seen.

[@lallyji8051]

Amazing Video!!!! Best one explaining Shorts! God Bless you man

[@meharimran86]

best explanation of short circuit on

[@015diesel]

Love this channel! I've learned so much from you and would like to thank you very much for putting the ti e and effort into teaching us 👌

[@sharymens8187]

How is the video called for tracing power lines as mentioned at 27m50s?

[@DjRussieRuss]

Thanks for the knowledge! Great explanations

[@robertobarros9946]

Really well explained and helpful. Appreciate the effort in making this. Cheers

[@j.lietka9406]

The voltage injection technique should be used only as long as needed? If you can, does it help to remove the CPU? Assuming the CPU isn't defective!

[@ARI-og5ze]

Thank you so much what a lovely explaining I'm a beginner and after watching you for the first time I feel like i can fix things now 😂 thanks bro all love from Algeria ❤

[@andersdoverud9046]

At 30:03, shouldn't you say "90mV" instead of "90mA"?

[@wayland7150]

That confused me for 3 seconds too.