this is the easy way, and you need to take it out always to test it, because the short on the gate to drain or source it will not let you turn on the laptop, and the chargers on dell, need to have the correct watts if not the laptop will not pass the 19v power rail or turn on any other power rails on

I don't understand the process you are referring to. You mean injecting 1V directly to the output of that coil? And what do you get with that? How do you tell if the CPU is good from there? Thank you.

It's never the CPU... unless it took 19.5v to the face because a power stage failed... in which case it's probably the CPU 😅

@@Adamant_IT well I'd like to say that cpus are indeed a complicated thing especially when it come to their psu and it's Power management drivers... one thing we should know is the fact that cpus require more then one low voltage (0.8v to 1v) with higher / lower side MOSFET ( you had a different thing you has probably a dual mosfet case in this "gaming" lol laptop ). I'd say try hitting that coil with a 0.8v or 1v and set the amps as low as 2A or 3A auto and try powering it on again before deeming it a CPU failure. again, thank you for sharing and good luck Adam.

isnt heat supposed to make the resistance go up?

@@dichoseadepaso That's true for metals, but semiconductors do the reverse.

@@man_eating_monkey oh i didnt know that! thanks

The CPU has an internal resistance of about 2-4 ohms - this is why all of the vCore components and capacitors will beep in continuity mode and look like they're shorted to ground. So if you see the main power rail at somewhere between 2 and 4 ohms, that should immediately make you suspicious that this might be CPU resistance, meaning you have a shorted VRM. If this is the case, you can't inject power because that power will go directly into the CPU. The easiest way to check if you have a VRM short is to measure the resistance to ground at a vCore inductor, and see if it's the same as your main-rail resistance. This is what we saw in the video, which means there's a very high chance of a VRM short. Because there's usually only about 4 VRMs at most, it doesn't take long to manually desolder the inductors and see if the short disappears. In the video, it disappeared on the 3rd VRM, so now we know where the fault is without having to inject power. Sadly, if the CPU has seen 19v from the charger, the chances of it still working are extremely small. GPUs are tough and will probably tank a zap, but the CPU is fragile and won't.

@@Adamant_IT Thank you very much for the detailed answer.

​@@Adamant_IT is it true when measuring the resistance in the second mosfet or current sense resistor of inrush limiter protection faze if • resistance < 1Ω short is in the main power rail and it's somewhat safe to injection • 2Ω < resistance < 4 Ω: clasic signe of shorted VRM (your case ) or cpu failure • resistance=0.9 Ω : gpu Vram or gpu failure of corse if there is a discrete /dedicated one in the laptop

Note quite that simple... vCore is low voltage, _high amps_. Your bench power supply would need to be able to to 15-20amps, which is a lot.

​@@Adamant_IT I'd try hitting that coil with a 0.8v -- 1v right after seting the amps as low as 2A or 3A auto ( it's a gaming laptop it can take 3A) and I'll try & power it on again. in a nutshell, tricking the cpu Vcore power rail . Vcore power is supplied, CPU is bamboozled thus pc is on. 1100010100110, Praise the Omnissiah.

​@@drmoose7233is there any video in youtube someone does that?

VRMs - at least "fancy" ones as these - have over current limits. So even if the CPU would be shorted (which I don't think it is, since 2.5 Ohms is a fully normal reading for VCore), the VRM would prevent excessive current.

hello from a used laptop lcd? or what kind of blacklight

It was a 90w brick, which should've been enough to at least turn it on. Most Dells can run on under-sized chargers in low-power mode.

Dell laptops will turn on and reduce the CPU power if a lower capable charger is connected,

It's a Sequre SQ-ES126 👌

@@Adamant_IT Thank you very much ;)

I did test another BIOS battery in it, but I didn't make note of it because it didn't make any difference. It would've been worth pointing out though, because yea modern Dells do behave like this with a stuck-BIOS.

We've already figured out what the short is in this case - it's the VRM power stage. It's failed-short, so it's essentially behaving like a wire bridging the 19v rail directly into the CPU.

The short is not directly to ground, but to CPU Vcore, which has a very low resistance to ground through the CPU. You can always have a short between different power rails, not just to ground.

Brain engaged. 50 points awarded

he wears a bracelet. Verge style

I did actually pop a different BIOS battery in there while testing, so was being checked with a known-good cell in. I had one RAM module in for testing, but it should've turned on with none in anyway.

@@Adamant_IT but what about cmos battery reset (s.c. terminals)?

desoldering the power stage meaning what desoldering the high side mosfet or just the coil that diliver the power to silicon ? also wouldn't the internal control detect the absence of a power source for the CPU in such a scenario? And how would the internal control (driver) and main power rail respond in each case when the silicon chip (CPU or GPU) has or hasn't experienced a 19V hit, indicating a short through silicon? Would a DC power cable be fast enough to protect the CPU, GPU, or PCB

@@drmoose7233 That chip has the driver, the highside mos and the low side mos, all-in-one. If you have the low-side mos shorted (not this case), if you power it up you risk the drive open the high side mosfet and you have a dead short to ground. So, you should remove the entire power stage (single chip) to avoid the risk to do more damage. Power supply for CPU and GPU are multiphases nowadays. So, it's possible that the system works even if you remove one phase. I have a gtx 970 at home who have 5 phases out of the original 6 (this because it was impossibile to rebuild the last one since the pcb has been seriously damaged) .... and it works fine (I just limited a bit the max watt available using power limit). Of course, it depends how the psu is designed ... sometimes it could require some modifications. About the damage to the CPU: there is no a straight answer. You could have a shoprted cpu/gpu, you could have a cpu/gpu working badly, you could have ram problem (cpu/gpu has an integrated controller for the ram so, the voltage could it also this part of the chip ... and maybe you could think it's the ram but it's not). Could the protection be fast enough? Depend on the board and also luck. Anyway, usually is the main power controller who intervene in this case (the one who receive pgood signals from single power rails all over the board).

@@larrywildman4381 thank you for the valuable answers ...much obliged

It shouldn't matter, the device should reach S0 (powered on) with no RAM - however, yes there was a single module in there.

Dell laptops have a data line called OneWire going to the charger, which allows communication between the two - so the laptop can tell the charger to switch off because of a power fault.

Just a dumb thought, but could the battery be required for the controller to be satisfied? Battery is probably toast as you said, but the smart parts of it should still be working?

If you're UK based, I can certainly try, postal address is on the website 👌

@@Adamant_IT Sadly not in the UK, I'm in Southeast Texas USA and can't seem to find a skilled pair of hands locally! Love your videos!

@@bigal1863 NorthridgeFix is in the US. Haven't used them but their videos show good work.

@@bigal1863 Try to contact Louis Rossmann in New York. He is expert in MacBook repairs but he might help you with others as well. Give it a try.😊 kzfaq.info

@@markusstrobl1067 I appreciate the referral Markus!

8.2v on PPBUS_G3H means the SMC isn't running (needs to be 8.6) and 3.10 on SMC_reset_L is also a bit low, so yea I'm thinking the SMC is stuck in reset. I'd start by reflowing U5110 and seeing if it all comes good. Also check PP3v42 going into U5110 at pin 1 to make sure that's at 3.42v as well.

@@Adamant_IT Hi adam, I can confirm that there is a capacitor missing (C5127) which is connected to the U5100 via the "GND_SMC_AVSS" circuit? Remember im a noob so i cant be sure what im saying is electronically correct. Does this sound like I have found the root issue? Would you happen to know if a capacitor like this is an easy replacement? I do have a donor board but its from a Macbook Pro A1278?

Not had problems with mine, but it's a cheap meter, so I wouldn't take it into battle, per se.

I think that "turning off" thing is just a FLUKE :)

You can't bridge in place of a voltage regulator...

Find the model number of the motherboard and google "model number schematic", and there's a good chance you'll find forum links. Quite a few repair discords servers for youtube channels like this where you can ask nicely as well, and people will check their collections.

@@Adamant_IT thanks

Without ram it still turn on but don't boot

@@limwellz Not always. I've seen laptops not even wanting to turn on without RAM. Mostly ACER (i think, it's either ACER or ASUS)

@@HoboVibingToMusic it has power but won't post that's what i meant. the problem with this laptop is it doesn't want to get powered same thing with my mcbook pro

This is correct, but BIOS circuits are bad and can require 3v on-the-dot, so they're actually incredibly wasteful of a CR2032 which is 3.2 max, 3.0 nominal. 2.9 or over is normally good enough, but when you're diagnosing, assume anything below 3 is suspect.

lol i'd round of numbers. there 3 Volts. ; ) it's not noted as 3.00

3 week wait for new chips, CPU's seen 19.5v and very likely dead... dunno. I'm taking a pass on it, but if I didn't have numbered time it might be worth a swing.

In the same way that a car engine can run with half the cylinders not firing. It's not going to run very well, but it can run.

@@Adamant_IT Oh, OK - Thanks. I've been watch videos & reading on 'electronics' electrical things for years. Truly Not my forte', lol but i find it Very interesting. Cheers!

If it had been the GPU, or if the power stage had shorted to ground, I'd say the odds are good that the chip were ok. But the power stage was bridged, and the CPU doesn't like getting zapped. So yea, unless you're happy to wait 3 weeks for new power stages for a hail-mary, it's not really worth continuing =/

Yea this one's being sent back. Replacement mobos are sometimes out there, but I generally don't go down that road with gaming laptops, because you never know the history of a second hand board, which is likely to cost a few hundred. Big roll of the dice for something you need to warranty.

@@Adamant_IT u get paid some? because ur wasted time i mean

Yes he is

@@gavinstirling7088 buddy

@@gavinstirling7088 I admire you ....collegue mate.....I do the same job here in italy ....i do servicing on tv and monitor and hifi equipment...fine business

listen mate have you never found any polimer cap failed on motherboards in your experience? which are the most common fails on motherboards you experienced ? which are the most common fails on pc's motherboards in your opinion and experience?