How To Find Shorts in VRM Circuits like a PRO. Simple to follow Theory and Practical Short Tracing

Рет қаралды 7,271

3 ай бұрын

I have a Motherboard with a short circuit in the VRM. It's easy enough to diagnose the fault but not so easy to find the actual shorted component. In this video we look at both theory and practical short circuit finding in a multiphase VRM. Learn how to diagnose this type of fault, then I look at five methods to locate the actual short. Only two of these methods worked and you may be very surprised to see what they were! Watch ALL OF this video and you will be able to locate VRM shorts like a pro! Skip parts and you can continue to mess around like an amateur, Your choice :-)
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Thank you
Richard

Пікірлер: 57

@chikaBurton 3 ай бұрын

Richard, thank you for all you do. This teaching from experience is something they don't do in schools. May you live a hundred years so you can teach us. Thank you again.

@1nzgninja 3 ай бұрын

Love your explanations, especially the diagrams..you obviously enjoy doing this and it shows in your content, thanks again

@humidbeing 3 ай бұрын

Thank you for explaining modern, multi-phase VRM circuits!

@LearnElectronicsRepair 3 ай бұрын

And thank you for supporting the channel 🙂

@bobpitt1261 3 ай бұрын

Excellent tutorial Richard, thanks.

@Lyndalewinder 3 ай бұрын

Very informative video Richard - thanks

@winlose3073 2 ай бұрын

Very informative post Mr. Richard

@cremvustila 3 ай бұрын

Excellent video, thank you Richard!

@LearnElectronicsRepair 3 ай бұрын

Thank you, I think this was one of my better ones 🙂

@cjh0751 3 ай бұрын

A very invaluable lesson . Thank you.

@LearnElectronicsRepair 3 ай бұрын

Thank you

@BlackOpsJuJu 3 ай бұрын

Nice Vid Great as Always Very Well Explained Thanks for taking the Time and Doing Such a Detailed Job Explaining it Very Much Enjoyed it :)

@martin87865 3 ай бұрын

Hi Richard, Fantastic live stream Sunday loved it. Have now got a ESR meter on order as I am working on a similar fault, 5V rail short to ground.

@GranCanariaUncovered 2 ай бұрын

I hope it helps you but rememebr the ESR meter only worked because the short was one side or the other of an inductor

@screen-protector 3 ай бұрын

Hi. I meant to buy this meter ages ago :D, I mean ESR meter you're using ;), but now I see I should buy it then and there ;). So, thank you for the video. And, will share it with my technicians as well.

@Dutch_off_grid_homesteading 3 ай бұрын

Heya, nice to see some differant ways for finding this sort on this MB

@warwickbunn1250 3 ай бұрын

Brilliant deduction.👏 From a valueless board with a fault to one of your best videos yet ! The run through of the different test options and why they wont work, even got through my head 😜 Plus with the diagram I really feel I can now look at a motherboard and start to understand what and where some parts are, like you've done with power supplies. Have you done a video running through of all the acronyms and what they do ?

@GranCanariaUncovered 2 ай бұрын

I haven't yet but hmmmm

@knightwar3 3 ай бұрын

I was expecting to see that shorted mosfet to glow in the phone's screen but it didn't it looks like an esr is a must to find vrm short btw what i like about socketed cpus is that you can focus on the motherboard only if there's a short circuit. Thank you for showing all the possible methods

@Lightrunner. 3 ай бұрын

Great instructions about repair a pcb and find the fault 👍👍👍👍👍

@LearnElectronicsRepair 3 ай бұрын

Thank You

@ubiquitouy 3 ай бұрын

Similar to your ESR method, I think it would be possible to inject the sine output of an AD9833 or other 100Khz oscillator at half a volt into the common side of the VRM inductors. Then check the voltages on the FETs with meter or oscilloscope. AD9833 modules are very inexpensive compared to an ESR meter.

@LearnElectronicsRepair 3 ай бұрын

That sounds like a good idea for another video 🙂

@darek7524 3 ай бұрын

ESR meter i didn't know this method before, thanks for the tip.

@LearnElectronicsRepair 3 ай бұрын

I think i kinda accidentally invented that method, or at least I figured it out independently. I've shown it on a few videos previously, the first time was at least a couple of years or so ago. I've not found any older videos showing that on KZfaq but most likely I wasn't actually the first. It's kinda painfully obvious when explained to you and it works 100%, Enjoy 😉

@harmsprakel1109 3 ай бұрын

thnx greetings form the netherlands

@BasicComputerRepair 3 ай бұрын

I'd love to have an ESR meter. Very good explanation of VCore.

@kas262 2 ай бұрын

Hi Richard What about grounding the output of one coil when injecting current. That way amps do not flow through cpu and all the heat goes to shorted mosfet, protecting the cpu and you can better view the heated mosfet Please see "Dell G15 5525 no power, board repair" video from Sorin at 04':30 Thanks for your ongoing work and creativity

@sergei149 2 ай бұрын

I would want to see if it was possible to measure the 2 suspected MOSFETs with ESR meter and if it could point to the faulty unit without disordering both

@RWCSNZ 3 ай бұрын

11.46 i got up to answer the door lol

@LearnElectronicsRepair 3 ай бұрын

Actually it is not the door, the bump bump bump comes from the cafe next door. If I told you wat it really is you may not believe me, but think about making coffee and you may figure it out...

@weerobot 3 ай бұрын

Cool...

@Yarogum 3 ай бұрын

super=)

@shesoyam 2 ай бұрын

Awesome Video!!! Method 6: Inject 3A/5A nothing gets warm. remove MOSFET one by one 😭😭 Question. I see a Peak ESR70 on my used market..You'd recommend it? I'm doing some research on it rn I see the resolution is Resolution down to 0.01 ohms compared to the MESR 100 (Higher Resolution up to 0.001 ohm). You think it'll suffice if used in exactly the case above you showed?

@jonathanrose456 3 ай бұрын

❤

@TheElectronicDilettante 3 ай бұрын

Here’s a serious question as, I am still learning the subtle nuances of the fields of electrical/computer engineering and electronics. To diagnose this type of short, if the critical components are isolated and/protected from testing or probing, would it be possible to find the short by one of these 2 ways?? 1.(Smoke Method) Back in the day in the automotive industry, a common technique for finding shorts to ground in body or chassis electrical circuits, was to apply 12v at a huge current and literally look for the smoke. As crude as it sounds, it’s highly effective. Could something like that be used to find a short to ground on a pcb? Instead of smoke use a thermal camera and use just a tiny amount of current? 2. Apply a minimal positive voltage(no current) to the ground plane or terminal of the pcb, then start probing for voltages where there normally shouldn’t be any? Any input is greatly appreciated. Thanks for all your videos. Sorry this is so long.

@LearnElectronicsRepair 3 ай бұрын

1. No. In fact this is just likely to cause smoke even where there is no fault. As there will be components (in this case the Northbridge/PCH) connected to Vcore and you can't disconnect them and the need for example a 1V supply, you can't go sticking 12V in there, OK? 2. I'm not sure what you mean here, are you suggesting connecting the Positive terminal of your power supply to ground on the board, then go probing around various points with your test lead connected to the negative terminal on your PSU via a volt meter?

@cjh0751 3 ай бұрын

Am I right in thinking the MOSFETs are chopping the 12v waveform to supply a voltage that the CPU can use?

@LearnElectronicsRepair 3 ай бұрын

Yeah you can think of it like that. The high side MOSFET turns on first, and current passes through the inductor into the load and the capacitors on the low voltage output rail. However when you pass current through an inductor, the coil and/or former will magnetize. This stores energy in the magnetic field and effectively creates a potential (voltage) across the coil in reverse direction to the applied voltage. So can consider that initially all the voltage appears across the inductor, none across the load, and the reverse voltage decreases as the coil magnetizes, so after a short period of time there would be no potential (voltage) across the coil and all of the potential would be across the load. Got that? OK so we don't want that to happen therefore we turn off the high side mosfet before the coil can fully magnetize. We now have stored energy in the magnetic field of the inductor. When we turn off the high side mosfet no more current can flow in to it. We now turn on the low side mosfet. The magnetic field collapses and in doing so generates a voltage in the same direction (polarity) as inital 'charging' voltage. This causes current to flow out of the inductor, charging the the output capacitors and supplying the load. The low side MOSFET completes the current path to the other end of the coil. I made a video recently explaining this in more detail from a practical point of view without getting into maths. Kirchhoff's Law vs the VRM. You will probably like it kzfaq.info/get/bejne/q5enhJykubaUYGg.html

@letsinstall6368 3 ай бұрын

Did someone actually left the sticker on the CPU under the heatsink?

@tokin420nchokin 3 ай бұрын

What type of digital microscope are you using? Seems like it really focuses in fast.

@Pickle136 3 ай бұрын

he uses a camera mounted overhead of the desk that he can zoom manually. To his left he does have a optical microscope. Im pretty sure he reviewed some of the chinese microscopes at one point.

@anthonyshiels9273 3 ай бұрын

He mentioned Adonstar. Amazon stocks a range of them.

@LearnElectronicsRepair 3 ай бұрын

Yep, what Pickle136 says 🙂 I made a video about it 'How To Set Up A KZfaq Recording System for the Workbench' kzfaq.info/get/bejne/r9iGqs57zsqnaY0.html

@tokin420nchokin 3 ай бұрын

@@LearnElectronicsRepair appreciate it!

@LearnElectronicsRepair 3 ай бұрын

@@tokin420nchokin You're welcome. I made that video in response to various subscriber comments/questions. I hope it helps anyone wanting to do something like this on KZfaq.

@grahambambrook313 3 ай бұрын

Would "Mr Bleep" have helped with this?

@LearnElectronicsRepair 3 ай бұрын

Mr Bleep is not a low resistance (milliohms) meter it is a continuity tester with diode tester function, so no it wouldn't. Another one of my popular devices was the 'Incredible $1 short finder'. That has basically the same resolution as the Vici milliohm meter I used in this video so that wouldn't have helped you either. By far the best method is the ESR meter as I demonstrated as you just grab it and use it, it does not inject any appreciable amount of current into the device under test, and it gives a very clear and obvious result. The other method of bench PSU + millivolt meter also gives a very clear obvious result but you need to attach more wires, set your bench PSU to a safe output voltage, and really need a high sensitivity multimeter, my Aneng AN8008 reads down to 0.001 milliVolts which is specifically why I bought it as I have several other meters that don't have that. You need at least 0.1mV resolution to get a usable result I would say.

@mikebond6328 3 ай бұрын

No. It’s the same as the diode/continuity tester on the multimeter.

@LearnElectronicsRepair 3 ай бұрын

@@mikebond6328 Mr Bleep is not quite the same, it's how diode/continuity mode SHOULD work on all multimeters, but you are quite correct it won't help in this scenario

@Dutch-linux 3 ай бұрын

@LearnElectronicsRepair 3 ай бұрын

Hello 🙂

@genxmonk70 3 ай бұрын

This man trash talking LGa775! I had my Core 2 Duo E8400 running at 4.608GHz 24/7 stable on air. Im sorry, just busting chops. I know you meant resale value as a collectible. Thank you for qll the great knowledge, by the way. (Edit - i am actually really proud of the 4.6GHz thing. It took weeks of tweaking and testing and making minute qdjustments to values.)

@LearnElectronicsRepair 3 ай бұрын

Don't get me wrong, some LGA775 are valuable and collectable - in particular the ones which support Core 2 Duo/Quad, Core 2 Extreme AND have AGP! I've found quite a few that are LGA775 plus AGP that only support Pentium 4, they are saleable but not so valued. Also I found three so far ASrock LGA775 with Core2 support, with PCI, AGP and PCIe slot. I kept one for myself, these are rare and one very nice thing is you can fit both AGP and PCIe graphics cards at the same time, set up dual boot and have the PCIe card running under XP and the AGP card running under Windows 95 or 98SE!

@Lightrunner. 3 ай бұрын

You need more CPU Power. Your Billy Boy win dooow_s or game need this. More Power after 24h2 update🤣🤣🤣 ohhh man ........ ohh i forgott, you need a bigger harddrive🫣.