The Ultimate Short Circuit High Side MOSFET Tutorial Guide. 10 ways to find the faulty VRM. GPU CPU

LER #222 In this video we will look at TEN different ways to locate a short circuit high side MOSFET on GPU and Motherboard VRM

00:00 Chapter 1 - Prelude
02:16 Chapter 2 - The Diagnosis
16:58 Chapter 3 - Finding The Shorted VRM
21:10 Chapter 4 - Understanding The VRM Circuit
33:59 Chapter 5 - What Is Shorted High Side MOSFET?
38:27 Chapter 6 - The Problem
39:25 Chapter 7 - Identifying VRM MOSFETs And Drivers
44:59 Chapter 8 - Method 1
47:18 Chapter 9 - Method 2
48:34 Chapter 10 - Method 3
49:41 Chapter 11 – Method 4
50:41 Chapter 12 – Method 5
53:26 Chapter 13 – Method 6
58:23 Chapter 14 – Method 7
59:33 Chapter 15 – Method 8
1:02:47 Chapter 16 – Method 9
1:04:03 Chapter 17 – Method 10
1:05:26 Chapter 18 – Bonus Method 11
1:11:20 Chapter 19 – Epilogue

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

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

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

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

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Thank you
Richard

[davedave]

I’ve watched more tutorials than I can count and this is by far the easiest channel for people like me to learn from. I only wish I didn’t waste so much time on the other channels where content creators just assumed we’d already know what they were talking about. Thank you for taking the time to explain everything.

[iaingold]

Thanks so much for this video. I think it might be my favourite video on YouTube that I have watched. I am an electronics tech and have not used an ESR meter before... I am going to find one tomorrow. I blew a fuse on my new rx6700 card that I mounted a water cooling block on, using your knowledge and instruction to test the pins I got to deduce that i didn't have a 12v or 3.3v short but decided that what you were explaining would further my knowledge and understanding so watched intently to the end. I think I must have over tightened the screws (for fear of leaving a gap on GPU core due to thick thermal pads on VRMs etc.), I am now hopeful that the fuse was all that is needed. I measured my drivers and they all seem to be the same (with same part numbers at least). I am almost glad I broke my card because I have now found your videos. Thank you for being such a great teacher, i will try to pass on your skills to the students I teach and certainly be sharing with the enthiastic ones your channel

[tdtrecordsmusic]

excellent vid. Truly excellent.
whenever I come to a situation of having to remove a component like this, I use 2 soldering irons. (Also, puffs of air if needed to blast the solder off.) One iron heats the area and one goes for the pins. Typically, if I can't unsolder it is due to heat sinks, mainly copper pads under components. I wonder if u could have just put an iron directly on the ceramic(black) part of the mosfet. it's dead anyways so no worries about killing it, but this would put the heat where u want it and no where else.
Another method of diagnosing is signal injection. Grab the signal generator and put a frequency through stuff. This works amazing. Usually u can read anything. U will have to get used to what happens and learn to read the signals. Resistance shows as signal attentuation. Capacitance shows as signal frequency cutoff, U need to look at bandwidth to check that. Diodes chop ur signal in half. Best part is u can read circuit paths with very low injected signals. Actually U want to use very low currents. 10k or 100k input impedance(resistors). A scope + signal generator can tell u everything u wish to know about circuit layout and the state of the components.

[Todayisthelife]

I'm as green as it gets.... recently found I have cancer and lost my job so I'm taking this as a hobby. Man am I glad I found you! I have a 3090 to repair. Wish me luck!

[hamzalogo]

Watching this video at 3 am trying to sleep, but it had the opposite effect on me, got me so interested and hooked, hats of to you sir, and thank you for the amazing tutorial

[kriswillems]

For those that are wondering why the ESR meter was so good:
Because the mosfet is shorted you are in fact measuring between the 12v line and the vrm output. Both the 12v line and the vrm output have capacitors. The other side of all capacitors is connected to ground. So, your ESR meter is measuring the series of the vrm and 12v capacitors (and the ground in in the middle between the both capacitors).

[mansjacobsson]

Thank you for sharing. I'm a total beginner who is just eager to learn about electronics. I just want to be able to fix stuff at home. So I appreciate your time.

[kriswillems]

This is really good video. Honestly, I am an (fellow?) electronics engineer and have seldom seen such creative approach to finding shorts. It's great summary.

[dwightelvey]

I have yet another method. I've even used it to find the location of a short on internal power plains. I'll try to describe it.
This is even safer than the ones you've used. It requires no current through the components.
You need a sensitive meter. I've used meter that can measure 1/10 of a micro volt.
First locate the thinnest trace. I believe on these boards it would be the 12V side of the transistors. Set the power supply for the maximum current. and some minimal voltage. I usually use 0.4 V. In you case 5 amps should be enough.
Attach your power supply to the two remote ends of the 12V that is across where the FETs are attached. The supply should clearly be in current limit. I usually solder wires to make a more stable contact.
Now take one lead of the meter to the load side of the coils. Now with the other lead probe along the 12V connections.
Where the voltage measured it the point of the short.
I've used this method to even find a short that was as high as 1K ohms. It is all about getting enough current to see a voltage drop across the 12V trace. It works like a wheatstone bridge.
For internal layers, I will often choose the ground plain to drive the current across. I solder wires at two diagonal corners and drive diagonally. ( assuming a power rail short ). I'll start with one meter attached to the offending rail. the other lead I probe around the ground at various known ground points. I'll lay a string, held in place with small pieces of tape along the 0 volt line ( often a curved line ). I remove the supply and place it on the other diagonal. I then probe for the zero along the string. It may need zeroing in by measuring the other diagonal, again, for the exact component.
I used this method to find a 1K short on a burning board with 600 socket and several hundred more resistors of 1K.
The idea is that when the reference matches the drop across the high current line, it is like finding the point of contact along a series of resistors. You know that a lead is connected to one of the junctions so the minimum voltage is the same point.
As I noted, do not feed the current directly through the components. In your case some current will branch and flow through the coils so you'll need to also move the reference. It is hoped that the coils have more resistance than the traces.
Dwight

[ExtremeBogom]

Thanks Richard. Another great video, full of useful information. I've learnt a lot more about mosfets and their relationship with drivers and why there is often two/three mosfets working together.
You are a great teacher!

[ppaul]

About that welded driver IC, it might be easier to move the coil and other components for that phase one another unpopulated place if is on same power lane, or maybe with a mini grinder to destroy the case of the driver and try to unsolder the metal remains piece by piece the fused one might become easier to be removed but i woldnt put to much hope to come off without a chunk of pcb trace. Thank you for your videos, i wish there was a channel like yours 10-15 years ago it would made my life so much easier! most of your tricks i had to figure it out by myself but still i can find them useful being so well structured as a reminder. Good luck with the repair !

[baghdadiabdellatif]

i can't thankyou enough
God bless you greetings from north Africa (Algeria)

[manuforti]

Another excellent video. I have had 2 board where there is no way the hot air is removing a mosfet. Both cases have required a dremel to grind most of the mosfet away then flood with solder to float the remaining parts off. Not easy but doable. I watched a guy do it on a video, he was german but the auto subtitles and with a lot of pausing the video I could see what he was doing.

[chrirep]

What a GREAT video! I am a total amateur but I enjoy watching you as you explain it so well that is easy to follow even for the newbies.... YEAH?!? 🤪 Keep up the good work!!

[marsovac]

Haha i'm not an electrical engineer but a software developer. However after you shown the diagram and identified the fault, I tought "well just desolder the coils one by one and the short will disappear". I continued watching the video and right before the last few methods, where it become complicated, I was thinking to myself "hmm maybe I'm dumb...". And then you left that method for last, and pulled me a prank :D Perhaps it makes sense that they are difficult to desolder, but then it makes sense to put this method as first since it is the most obvious one, and explain the problems and then proceed with others.

[naidol]

Excellent. The circuit diagram drawing explaining each component and then how they packaged into chips we see on the pcb was the best part for me (novice). Look forward to video about removing the mosfet. 😊

[wantomek]

Another option is to bridge the coils together and inject voltage between DCin and the bridge thus protecting the GPU chip, but very thorough explanation. Cheers!

[davidhollfelder]

Great diagnostic strategies. Measuring voltage drop across each coil, is great .. similar to finding a parasitic draw on a vehicle by measuring millivolts across each fuse/ckt tree in the fuse box(es).

[zeferrum]

I cannot imagine how many hours went into this.. So much for the weekend only hobby!! Thanks so much. . keep up the great work. Martin

[technomad]

You are a legend .. Ive watched many videos on PCB repair .. This covers so much and easy to follow, so useful