CPU Vcore Repair in Laptops

[caspian]

Dear Forum Members,

I have successfully repaired a number of 3v/5v circuits so far. But I never had success in repairing CPU Vcore buck converter circuit. I mean its Mosfets and controller IC. I tried on various laptops with no success.
How much success rate did you have in repairing CPU Vcore circuit in laptops?
How often do such repairs succeed?

Thanks

[mcplslg123]

Re: CPU Vcore Repair in Laptops

Cpu vcore problem is bit complicated and lots of components are invovled like Vcore IC, fets,SIO,PCH,Bios to name a few.I always check the input requirement of Vcore IC first, VR_ON signal, VS voltage lines etc.Shorted caps in the vcore section is also a probabilty(recently missing vcore in a lenovo G570 mb was 'coz of shorted capacitor).

As far as success ratio is concerned , most of them can be solved but definitely all cases i too could'nt solve.

[caspian]

Re: CPU Vcore Repair in Laptops

Thanks,
I meant: success rate only when we see some CPU Vcore Mosfet is shorted.
I tried replacing both controller and Mosfets in a number of laptops, but I did not succeed so far. The lack of success was due to some mistake that made the CPU Vcore circuit fail again.
I personally think when a CPU Vcore Mosfet becomes shorted, a lot of things get damaged in the circuit that we cannot guess. I mean somethings in addition to controller and Mosfets. That is why the problem returns after repair. That is why I think such a circuit is not worth repairing.
To find all the faulty components, we have to waste a large number of ICs and spend a large time.
How often do you succeed in repairing CPU Vcore when some CPU Vcore Mosfet is shorted?
Is it worth repairing considering the ICs we have to waste to have a number of tries?

[mcplslg123]

Re: CPU Vcore Repair in Laptops

Well shorted high/low side vcore FETs cases can also be resolved majority of times. Things may not be same in case of soc mb. In fact most of these cases are of burnt fets and you have to be very careful in cleaning the area and ensuring that resistance on all pins of FETs are proper. I change all vcore fets with vcore ic at one go.

[piernov]

Re: CPU Vcore Repair in Laptops

Typically you have to replace the MOSFET drivers (or controller if drivers are integrated) and all the MOSFETs, so that you don't leave a half-dead component and you avoid unbalancing issue due to different characteristics of the new parts. Also, use MOSFETs from trustable supplier, no random MOSFETs from eBay/Aliexpress coming from random batches or desoldered from dead boards.

If MOSFETs short, there's a high chance CPU is dead too, especially newer models (Haswell and up), which you cannot replace because they're usually soldered.
Pentium 4 could take 12V with no issues, 3 times in a row and they would still be alive. That's not the case anymore…

[caspian]

Re: CPU Vcore Repair in Laptops

maybe, CPU gets damaged mostly and that is why success rate is low. is this true?

[jasko_jacker]

Re: CPU Vcore Repair in Laptops

I find very difficult to identify the problem if it does not concern the mosfets or components that can be tested, especially in the cpus (from the sixth generation) with the integrated pch. I am considering the idea of investing in the purchase of a debugger for intel processors

(https://www.ebay.it/itm/Intel-Itp-xd...426675064?hash = item41fd8bd978: g: FUkAAOSwqrVclN5d this is only a part of what is needed)

(https://www.ptsecurity.com/ww-en/ana...-theres-a-way/)

but I have to understand the real possibilities of use. For example I have a hp with missing vcore and there is no documentation about the NCP81206 controller it all seems in order apparently there are all the signs but the problem persists, with a debugger (in my idea) I could know right away if the cpu (cpu + pch) is damaged.

[piernov]

Re: CPU Vcore Repair in Laptops

If the CPU VCore voltage is straight up missing (but the enable signal is present) it can be a defective CPU: the CPU itself sets its core voltage through SVID (it uses power from VCCSA rail at that point to work, not VCore). Hard to tell if the CPU is the problem, but if the power sequence is ok until VCore and the VCore controller has been replaced and there is no full short to ground, then it may be a CPU issue.

[mcplslg123]

Re: CPU Vcore Repair in Laptops

maybe, CPU gets damaged mostly and that is why success rate is low. is this true?

That's precisely what i said at post#4

[caspian]

Re: CPU Vcore Repair in Laptops

thanks
Because of the facts that recent CPUs are soldered and cannot be tested, statistics are important in such Vcore problems. If experienced members confirm that: "CPU gets mostly damaged when there is a shorted VCore Mosfet in laptops", then we become encouraged to replace BGA CPUs more often in such cases.

[mcplslg123]

Re: CPU Vcore Repair in Laptops

Replacing SOC's are not much viable as they are priced very high and reliability of the so called new soc's are very poor. SOC's are not compatible across all boards-they are tied to specific boards-so replacing them from a scrap board is also not possible to a great extent.

[jasko_jacker]

Re: CPU Vcore Repair in Laptops

It's a nightmare with these bga. With old cpu on socket a fault was very rare. I Think the most fault regards U cpu with a hub inside, I don"t know the percentage of faults between cpu Power lines and hub Circuit.
Probably some causes are hight density and solder stress but I Think the programmed obsolescence is the first cause.

[caspian]

Re: CPU Vcore Repair in Laptops

If recent BGA CPUs cannot be replaced properly, it will lead to a high percentage of non-repairable laptops in repairshops. is there any solution?

[jasko_jacker]

Re: CPU Vcore Repair in Laptops

on ebay there are hundreds of broken cards or even entire notebooks, (my business concer to buy a defective notebook repair it and resell as refurbished). Today I received a card of an asus k501u that I had purchased for the CPU for repairing the HP starwars. I'm starting to test the power lines and it's ok then I find a short on + 3VA_DSW that is connected by a jumper with
+ 3VDSW_VCCPDSW and then directly to the CPU / HUB.
I isolate the signal and find that the short is located on the side of the CPU / HUB, in the end, unusable cpu, other money thrown away

[caspian]

Re: CPU Vcore Repair in Laptops

So, my question in Post #13 becomes more important. But I am not experienced in BGA repairs. Therefore, I need experienced members explain how to replace recent BGA CPUs. Is there any solution? or we should forget about replacing such CPUs?

[jasko_jacker]

Re: CPU Vcore Repair in Laptops

The first problem is how to find a good cpu with reasonable price.
I solder these cpu with a dedicated temperature profile to prevent the chip from bending.
If I have to re-solder a non-perfect chip, I use a special glue for high temperatures and an aluminum structure that prevents the chip from bending.
After welding, I remove the structure.
As you can see from the pic the result is acceptable

[mcplslg123]

Re: CPU Vcore Repair in Laptops

Replacing them is though bit tough but have done a couple of times with no bending.But met with succes in only 1 LA-992P mb so far. Yesterday only, i replaced i3 bga cpu+hub on quanta Y11 mb but the cpu turned to be defective(HUB actually). Bought it from aliexpress-so the money goes down the drain plus the time and skill wasted for hours. As @jasko has said, it is the sourcing which sucks with these SOC's.

[caspian]

Re: CPU Vcore Repair in Laptops

Do you think the designs of current BGA machines must be modified to do replacement of the recent BGA CPUs?

[mcplslg123]

Re: CPU Vcore Repair in Laptops

Do you think the designs of current BGA machines must be modified to do replacement of the recent BGA CPUs?

Technology keeps evolving and thats the best part with technology-so the machines will also change. The current bga machines are sufficient enough to replace bga cpu's as long as you have the right SKILL and to some extent experience. For newbies, I'll recommend to do it on a known bad mb and bad cpu to perfect their skill first as the cost of damage is too high to bear.

[caspian]

Re: CPU Vcore Repair in Laptops

I mean modifications such as:
- Chip Alignment: because recent chips have very high ball density. are better cameras are required to align such chips?
- Applying Heat: because recent chips have two heterogeneous parts
- Temperature Profile
- Shape of Nozzle
maybe the current BGA machines get outdated and new models of BGA machines are required.