Short on main rail, except the CPU is dead :( - LFC
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- เผยแพร่เมื่อ 25 ต.ค. 2021
- Fail video, but a great example of looking for and diagnosing failed VRM mosfets.
Sometimes a main rail short isn't an easy one, because the damage is already done.
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With 1.7V Vcc Core, my Pentium 4 used to run a couple of games, toast the bread for my sandwich and heated the room as a complimentary.
My first gen i7 was like that, the heat was like a radiator and that was with just a browser open, was worse when gaming :P
You say that like current hardware doesnt function as space heaters....
It's never the cpu...
...until it is
It's never the CPU. Except when it's had 8.6volts into the system agent rail 😅
Yeah. I started working with computers when the Pentium 3 ruled the world, and back then it was never the CPU.
Had a c2d 2.26 fail once, it would boot but was unusual, my partner the honest genius simply looked at what it was doing and said, "bad cpu", he was right. Easy to replace and problem solved.
Had a Skylake i3 desktop with one bad CPU core. Running it as a single core worked fine.
@@Adamant_IT i´m not familiar with that overpriced Apple shit. Do those expensive boards not have over voltage and over current protection for the cpu and ram ?
There is no failure on your analysis,you have superb fault finding skills!
Sorry for the dead CPU, but it was a very interesting diagnostic follow through, thank you Graham!
Quite interesting to watch you work, and yes TH-cam, I definitely want to see more of Graham diagnostic services and repairs.
27:17 Ooof 1.7 volts on the CPU Vcore , yep dead cpu now 💔💔
Nah, the CPU VRM actually is rated Vout = 1.85V max. So getting that voltage reading on the CPU Vcore chokes is not the end of the world ;)
1.7v on the CPU VCORE rail is the correct voltage according to the schematic. It doesn't mean the CPU is going to work now.
Thank you for your job, your yt channel has great educational value and you’re awesome at explaining things, it’s easy to understand even for non english native. Cheers
I love how you work and how you explain every step to resolve the problem, you do super interesting videos! Thank you for sharing your videos, I am learning thanks to you!
Very informative and descriptive. Keep it going and the good work. When I saw the fan spinning, hope came to mind but back of my mind I thought probably not. You were right all along once you made the probable diagnosis.
I watched about 2/3 of your LFC videos hehe. Thank you for them 😁😁
Fan Spin! (to quote Louis Rossman of Rossman Repair Group) ...
good that this Macbook still has a removable SSD instead of soldered Flash chips ...
Graham you know your stuff great viewing and learning and I still never owned any Apple product and will continue that way
Damn it Jim! I'm a doctor not a repair man!
Northridgefix has encountered the same problem and cursed how Apple can build such a piece of crap that is destroyed by a Dollar mosfet. His website and knowledge are incredible, I learn a lot watching him (and you too).
Thank you for your job I'm just learned something new.
Nice diagnostic explanation. Thanks a lot.
Best regards, Nicolas
Nice instructional video! That's why I like laptops with socketed cpu even if it's old cruddy core2 duo. dead cpu means just two second to swap in another spare el cheapo cpu.
100-200ohms is very often the 1.05v PCH supply on these macbook boards, just for future reference. The PCH will sometimes visibly crack too when they get fried
I thought exactly the same thing when I saw a price 200ΩM.PCH dead short took the cpu with it. Too sad
Another confirmation of a failed CPU is to lift the heat sink and check for a crack in the glass surface of the CPU.
Interesting and informative explanation on working on a Mac. Something to absorb for the future usually I don't work on macs.
Really super thanks
Great video once Again
Amazing logical board repair video step by step👌👌👌So low price PPBUS G3H also means a dead cpu, due to a PCH fault. Maybe if the initial reading was close to 8v, that would mean a fault in the integrated SMC. Anyway, your effort was amazing and thank you for sharing it with us
Thank you!
Great work 👌
Great troubleshooting video
Great video bud very informative
Very interesting bit of detective work. Thanks.
I love your fix computer shows
Interesting movie GRAHAM. we are waiting for more to come THANKS
thanks your a good teacher I really like your vids
Great video! There's always things to learn in the failures. Definitely do more videos where you don't fix the problem. The diagnostic steps and thought process to come to the conclusion it's not repairable is just as valuable as the ones you repair. Out of curiosity what is the steps moving forward? Can the CPU be replaced with a donor? Can you order just the CPU? Do you need to replace the whole board? Thanks!
Interesting video! Seems strange that Apple doesnt build in more protection besides that mosfet to prevent the CPU from getting cooked if it fails. Great you showed a fail as well! Looking forward to the next one, keep up the great work.
If you watch some of Louis Rossmans videos, you dont longer think such stuff is strange 😅
He was a Video uploaded a day ago "A1708 MacBook Pro preventative maintenance PSA" where he rants about the flaw that Apple has high-powerrails next to datalines 😅
literally its not only apple in no laptop or computer is any protection on the CPU power rails after the mosfet. Am working in Computer repair and u won't find any fuse or anything there.
Why should they? Standard apple warranty is only 1yr. No need to make it last.
@@geraldh.8047 But that's the point. Allegedly, Apple's build quality is highly regarded yet in reality it is no better than the next manufacturer. In reality, what effect then on cost is to add a single in-line fuse?
you don't understand... think different: the cpu is the fuse. BRILLIANT!
Thanks!
Thanks 👍
When i had to find something on the board like burnt capacitors or anything like that, i use my phone cam in macro mode then a little zoom 🤣
Wouldn't it be easy to install a transient suppressor diode into the circuit where are voltage sensitive stuff installed? It would not cost much money for the factory. That way, those diodes would save CPU, GPU, RAM, and SSD chips from getting that overdriven with too much voltage.
Completely agree. A TVS diode at least. Another option would be some voltage regulator IC capable of withstanding 5A. Unfortunately those motherboards were already built like this. Good circuit design engineers would not fully trust electronic components and would insist on adding protection circuitry in those critical areas. Let's hope they do in their future apps. All the best.
Great video! =)
Ah this reminds me of dealing with a Dell Precision laptop that end up having liquid damage on the 3.3V always on power rail and shorted the high side MOSFET, and what would you know? SuperIO chip is stone dead when 19V blasted through it and gets mad hot every time the laptop gets power!
(I can't just replace the SuperIO chip on those things as the BIOS image is inside and finding a replacement chip is already hard enough)
Very good. Could you do a video going over how you check all the smd components how to tell all the bad. Thanks
Hello dear Adam
I would like to know, what are the consequences when inadvertently placing the transistor in reverse?
It happened on a 2018 macbook air, I put the Q3431 upside down
That was super interesting thanks
Graham, how do you manually control the brio focus whilst capturing in OBS, do you have other software open or have you set up some form of hot key arrangement?
Currently using Logi Tune to manual-focus, but I'm considering going back to Logitech Settings, because the interface is less cramped. It's lesser of the evils though, webcams aren't really designed for this kind of thing - they're just still an awful lot simpler and cheaper than a "real" camera setup.
No Graham, there's a bad looking cap at ..... sorry, couldn't resist (ance) great vid
if both power rails are working correctly (not shorted), what are the next troubleshooting steps? Maybe you have a video on that?
Proves you can have the super IO happy with all the rails and turn it on and fan spin but the CPU or GPU? is burnt out /shorted. wouldnt the circuitry detect that too and switch off as every time i have a shorted CPU, it gets hot drawing the amps and the PS switches off.
Thanks
its always the PCH thats integrated to the CPU that fails.
Is a replacement Ebay board too expensive? There seems to be a lot of them for sale.
Ye, the customer is buying a new laptop, but I'll track down another logic board for this one at some point and rebuild it, failing that the screen and other bits will get used to fix another laptop.
Hi, i have an acer m3-581tg it won't turn on ... it has all the voltages for about 5 seconds and then it loses them. what could it be?
I watch a lot of your videos and have to ask why you chose not to look through the scope to visually look for burned chips? I"M a rookie and only repair for fun.I have meters and rework station but not the NICE magnifier on the stand ,but i still manage to fix about 70 % of laptops.Could you point us to where the schematics are found? and cost maybe?thanks you do teach good stuff just in a different manner.
Short to ground could mean the rail gets shorted and devices after that do no get overvoltage. However, that 1.7V doesn't look good. But it still might fixable if the issue is the buck converter driver IC or something in the surroundings. CPU Vcc lines are typically controlled and yes, it could mean CPU got crazy and asks for this insane amount of voltage or the voltage regulator is doing its job poorly and the CPU overheats and shuts down (not dead yet).
I would give it some more tests regarding the high voltage on the rail. But yes, there's very real possibility, CPU got too much and is shorting the rail by itself and that really would be the end.
I'd check the high side mosfets for shortages (which would lead to overvoltage on the relevant rails)
it turns out that 1.7v is normal on these things, and I confirmed it after seeing a bunch of comments. However, the sysagent rail definitely got zapped.
Short-to-ground only works if the short is actually directly to ground - in this case the mosfet was shorted from drain to source, thus sending all the power directly into the CPU.
Is it not worth replacing the CPU? I know BGA is a pain, and requires special equipment which you may not have, but would it be worth doing if you had the equipment?
Board repair 👨🔧 Super man
You can't save 'em all, but very interesting vid!
I must have magic fingers, because I can feel a 200 ohm to GND part lose it's chill with 1A running through it - lol -. I can't feel it with my right hand, but I can feel it with my left because the skin is thinner on the less used one.
27:37 1.7 - 1.8v for Vcore on these is fine. Yes it's damned annoying when you are in an S0 state with fan spin but brain-dead CPU. Not often much chance of surviving shorted high side mosfets
@pedro147 you are everywhere xD
🦘
thanks u
Which board or model Year? anyone know? looks like 11"
got it: --> A1466, 820-3437-B, 13" AIR, EARLY 2014?
''The CPU is going up in flames man'' 👍
Please be careful when "toothbrushing" the board like that ! You can easily knock off components, especially if they're corroded and the brush is hard - I screwed up a phone board this way and had to pay for it :))))
I work on the assumption that if a toothbrush can take them off the board, they were weak and needed to be reflowed/replaced. However, yes, I should warn people of this because they might not be prepared for that.
@@Adamant_IT Also, you COULD inject voltage even with a high-ish resistance on the problem rail if you don't exceed its nominal voltage (8.5v in this case). It will not get as hot, but the thermal camera might just be able to pick it up. Of course, it means you (might) destroy any downstream components if a FET is shorted. The CPU would've gone hot in this case.
I really appreciate sharing your knowledge. You have NO IDEA how this channel helped me through my LIFE.
I'm literally making income using knowledge from your content.
NEVER THOUGHT TH-cam WILL HELP ME RECOVER
I wouldn’t say a complete fail you got a lot accomplished just the cpu is out of you’re control but you did get everything else working
New name...... "Let's Unf*ck Computers"
Where do you buy your schematics?
I enjoy the troubleshooting and explanations, never worked on MAC. One question, other than not having one, why did you not replace the CPU or, can it not be done because of some insane APPLE reason...
You see how hard it is to solder/de-solder fuses off the board and they have 2 solder points (11:45)? Well imagine having 1000 solder points instead of 2.
Basically it's incredibly hard to swap a CPU with a hot air station like this.
that would require a bga rework station with stencils, a donor board with a working cpu because nobody sells that part new and a decent amount of time/labor....you factor in the cost of all that and you FAR exceed the worth of that macbook, the best fix for that would be to find a used working board for cheap
that has nothing todo with apple. but to desolder a CPU or a CPU socket u need Expesinve BGA reflow / rework stations and they a literally FUKN Expensive
Yeah, 2 reasons actually.
1. Apple/intel doesn't sell the replacement chip for purchase.
2. The CPU is directly soldered to the board, so is the RAM. Needs special BGA reworking tools and expertise to remove and install such chips.
Bonus Reason - Success ratio in the long run is laughable at best. To fix the chip to the board, you literally cook the entire chip far far above it's maximum design temperature,so that the leadfree solder balls under it melts and adhere to the contact pads on the board. Removing a working chip from a donor board and installing here requires atleast two such heating cycles that may kill the chip faster.
Ye. It's a matter of "Yes it can be done, but No it's absolutely not worth it."
What is the most likely low resistance one can measure around the cpu?
CPU vCore tends to be around 3ohms, System Agent varies, but is usually higher, somewhere between 20-200ohms.
The give away for if you're shorted through the CPU is when the resistance on the main power rail (PPBUS_G3H) is the same as resistance on the vcore or sysagent inductors.
@@Adamant_IT thanks Adam I appreciate your act of kindness
ouch x3 and rip cpu
Quick question: thought the CPU rail was a low resistance rail hence difficult to identify a short on it. Was this mosfet on a different rail?
There's multiple rails to the CPU. Vcore is the big one, and generally sits at 1-5ohms, which is why it always looks shorted. A "real" short, like a dead capacitor, would be less than an ohm. This shorted rail was System Agent, also known as Uncore, which is mostly cache stuff and other internal communications that aren't the cores themselves.
@@Adamant_IT Thank you!
It's an Apple, rotten to the (CPU) core!
It’s the only modern day computer that gives us an idea of what an Acorn Archimedes could have been like had they survived!
So, I presume this means that the computer is just completely toast, buy a new one. Is it possible to still recover data if something like this happens? Also, I've always wondered what happens to these unfixable laptops. Does the customer often just give them to you and they become part of your donor stash?
the SSD was removed so data "should" be fine. Not all SSD's are removable
Yea, these MBAs have removable SSDs, so I can put the SSD in another device for data recovery. If the SSD is soldered in though, you've had it.
👍
Could measure voltage over the current sensing resistor. To sense current. This could confirm short.
She's doneski, Steve.
1.7V vCore sounds like a FB issue to me. Had a GTX 580 kill itself over a bad FB circuitry; 0V on FB, it decided not to trip OVP or UVP and shoved 5,56V into the GPU
1.8v is actually normal for vcore on these boards
@@danandrei96 That doesn't make sense. Sure, PPVCC_S0_CPU is rated at VOUT max=1.85V, but that doesn't mean it actually runs at that voltage. After all, it's a 22nm Haswell mobile core i5 rated at 15W on the receiving end of that rail. Not even Haswell desktop CPUs with much higher power limits and much more cooling available to them run at 1.85V or should be run at 1.85V. Doing that will, at best, severely degrade these CPUs.
VID might be configured to 1.85V, but VID is not to be confused with VOUT.
@@Asyq normally I'd agree with you, and it's definitely weird. But I have 100% measured this with my multimeter right at the inductors on multiple fully working boards, and 1.8v is normal. These CPUs have about 20ohms of resistance so they need the higher voltage I guess.
@@danandrei96 Do you have a video of someone measuring PPVCC_S0_CPU on an 820-3437 that you could point me to? I honestly have a hard time believing that.
As far as I'm aware, only Haswell-E (and later on Broadwell-E and Skylake-X) CPUs have integrated voltage regulation circuitry.
Should name your channel eaglevisionIt
Sometimes it confuse me yet the computer work anyway with some low resistance reading only within the cpu domain
What would happen if u replaced the cpu would it work then ?
Theoretically yes, but at that point I'd just replace the logic board with a refurb board - which is likely what will happen to this device at some point.
You Said PPBUS_G3_Hot, where is Rosman :D
Wouldn't you know, why the hard drive wouldn't show up in the BIOS? It used to work, and then suddenly did not load up Windows anymore.
But not as we know IT
21:40 maybe it's better to remove L7630 coil?
Cool video but the title was a bit of a spoiler! 😂 Is it me the only one that likes to discover things as they happen?
I suppose, I tend to spoil fail vids, because I feel like some people would feel a bit robbed if they didn't get that "it works!" payoff. But for the people who are like, "I'm here to learn" they'll watch anyway...
@@Adamant_IT Fair enough. I watch every video to learn but to be entertained as well, so with the spoilers that part decreases a bit 😅, but I understand... Thank you!!
can you change the CPU?
Never the CPU until it is 😀😀😀😀😀😀😀😀😀😀😀😀😀
1.8v is normal vCore for the CPU on this generation of macbook boards btw
Saw a couple of people say this, so I checked a healthy one and you're right, 1.7-1.8 is the norm. Which is wild, but ya.
I just checked my laptop proccessor running at 1.319 volts.. at 3.6Ghz
I think 1.7 volts won't instantly kill the cpu, but maybe it will shut down the laptop
Hi,can you help me in getting this boardview please:
lenovo ideapad y580 boardview
You sent
It's mainboard no. Lenovo Y580 compal LA-8002p Rev:1.0
👍👍😎✌️
I'm not a tech, but I wonder why there is no safety circuit for this kind of fault, to prevent the cpu getting fried? I guess the answer would be like most apple products. They don't want it fixed, they want you to buy a new laptop.
It's so sad... you channel grew and your uploads are so rare now :(
Once a week has always been the schedule. Sometimes I get out an extra video, but that's always been 'extra'. Last week was a rare miss for me, where I had a rough week and just didn't have time to get a video edited.
@@Adamant_IT Okies. I'm really loving your content so I'm hoping you can ramp up the content in the future.
Me too , from all biard repair channel , love yours the most.
1.7v vcore, that thing is dead
You just need to get a new MacBook Air. Easy fix, 100%.
So sad that they dont have a protection for cpu😢
It's better for increasing shareholder value to nudge the user into buying a new one as often as possible.
hmm toth brush not a ggod tool dude as it will cause a static charge and can damage the electonics unless you have a brush that wont cause staitc build up
Not in the UK. The air humidity there is to high for a static discharge. And also, have you seen Linus's and Electroboom's attempts to damage electronics through static discharge?
@@marcellipovsky8222 ohh yes! Sparks can still happen but it would involve carpets and balloons.
It's Apple.....
Into the landfill it goes. I am glad Apple changed it's website so it looks like they are super green and really care about supporting broken machines instead of wanting to sell you the same crap year in year out.
are u only Rant because its apple? u won't find any motherboard in the world having anything after the mosfet to protect over voltage. its even impossible to implement that. Maybe you should study Electronically Engineering with focus on Computer Engineering u will see there is not way todo that
Yea tbh this isn't Apple's fault per se, this could've happened to any brand mobo. But still, there's plenty of other times where Apple are contributing to landfill due to lack of reparability.
+
Hi Adam! did you accept repair my laptop for service?
There's a good chance thermal cam would still find the short, even at 200ohms. As long as you took the heatsink off the CPU
I mean, at 1v 200Ohm you'd be passing 0.005a, so big doubt on that? Cracked PCH would be a better giveaway though.
you are from the uk? why you just casually use german words xD kaputt schmutz spritzen