Dell Laptops shut off

[vvmm]

Hi,

I have two Dell laptops that keep shutting off. Note that I have decent knowledge of hardware, software and electronics, so you can go very technical with me.
The ones I'm talking about are a Dell Latitude D620 and a Dell Inspiron N7010 with AMD Graphics.

Both have the exact same symptom: They randomly shut off. Sometimes exactly after BIOS boot, sometimes after logging in to Windows. It is very annoying and hard to determine the exact cause.

I cleaned them both of dust, replaced the thermal pads and the thermal paste, reseated CPU, RAM etc.
On the N7010, I did a GPU reflow, reball and even replaced the GPU chip completely with a brand new one. After the replacement, the new chip worked for a couple of weeks, but then started to shut off again. Temperature seems not to be an issue here. They are about 55-80*C all the time, I even keep the fan running continuously and case open.

I suspect that there is an internal power regulator failure of some kind due to a faulty capacitor or something else that should be extremely easy to repair, but very hard to find. I could not see what else should it be.
The D620 does not even have a dedicated graphics chip.

Does anyone have any kind of suggestion here? I'm very out of ideas and pissed off by these laptops, especially the newer N7010 that failed exactly one week after the warranty period ended.
Replacing the motherboard is not an option, a new one would cost me about 150$.

Any help will be greatly appreciated!

 

[BradtheRad]

case open.

Does this mean you leave hot components expose to still air? I cannot be sure if this causes heat problems in your units, but I have seen instructions in regard to other computers, warning us to put the enclosure panels in place during operation.

The reason is that the panels create a path so that the fan forces air toward components which need the cooling effect.

A chill pad might help your heating situation.

However you also state the problem appears soon after power-up. Therefore it might not be a heating problem.

 

[vvmm]

Yeah, I know what you say, but yes, it can't be a heating problem. At least not a heating of the CPU or GPU.

 

[BradtheRad]

I suspect that there is an internal power regulator failure

Yes, random shut off suggests it might be in the power supply. Since it is without warning, it probably is not something which Windows detects and does anything about.

I'm going on the observation that when my laptops have developed some serious problem, it would freeze, or go to BSOD. Or there would be a hang on startup sometimes, or refusing to respond to the On button other times.

Does anything different happen if you power from adapter only? batteries only? From both together?

Can you monitor voltage close to the incoming power supply? To see if voltage drops at the moment of shut-off?

Can you push or prod components to cause shut-off? This is a very risky thing to try, but it may help you track down the problem.

Can you insert a current measuring instrument in the power supply wires? This is risky, but you might observe a sudden current spike at the moment of shut-off. This could tip you off to a faulty component.

Have you examined logs of system events, application events, etc.?

Before the shut-off occurs, can you open Device Manager, and check the list of devices to make sure all are operating normally?

 

[vvmm]

I have two AC power adapters, the issue is with both, battery in, battery out, battery only. Doesn't matter.
Also, sometimes it shuts off even before BIOS completes POST, so it really doesn't matter if I have Windows, Linux etc. It does not get to load the OS from disk every time.
On certain occasions, pressing the power button lights the power LED and shuts off instantly and I have to press it a couple of times to start. And NO, the button is not faulty. Tested with "screwdriver contact" on motherboard pins.

Noticed that some large MOSFETS on board get really hot very quickly but I can't determine wheather this is normal or not, and even so, it is hard to determine what is the cause.

 

[D.A.(Tony)Stewart]

Abrupt shutdowns are all hardware related, either by sensors for voltage or temperature. ESD damage can cause excessive current drain as well. Load current spikes with supply caps wearing out can cause voltage drops.

It is unlikely BIOS settings are the culprit as I am sure you know how to set those.

Thermal resistance depends greatly on surface coplanarity and smoothness with micron tolerances.

If it gets past POST, I always boot from MEMTEST86+ CD to verify all hardware is OK, other than HDD.

 

[vvmm]

Yup, did Memtest, hdd test, even BIOS diagnostics from Dell. All fine. It is clearly something that can't be detected in software, but can't figure out what. I don't even have known test points to measure voltages or something on the board.

 

[rahdirs]

Hi,

I have a Dell Inspiron 15 Laptop(about 4 yrs old).I also faced a similar issue,that after powering it on it switches off within 1 min,sometimes it used to switch off before the windows lock screen came up.

Though unlike your case,i never cleaned my fan etc....Now i have bought a cooling pad & it is working fine.

Just sharing my case,even though you said that it may not be a heat related issue

 

[vvmm]

Thanks for reply, tried that also a long time ago, no luck.

 

[BradtheRad]

Noticed that some large MOSFETS on board get really hot very quickly

This suggests they are short circuiting or close to it. Mosfet gates are easily perforated by static charge. I imagine manufacturers install abundant safeguards against static, but no system is perfect.

Have you measured Ampere draw from the power supply? The easiest way I can think, is to measure going into the power plug. Obtain a spare plug of the exact type and size, use jumper clips to contrive access, so you can attach your meter.

Try reducing current draw to a minimum by removing all the external and internal devices you can. This may allow power-up to a stage where more testing can be done.

I believe normal draw is 2 or 3A (since a typical rating of laptop adapters is 3 or 4A).

Look for traces that could be 0V ground (possibly broader width). Test voltage readings to various components. I think 5V and 12V are standard. If you see 4.9 or 11.9 then that's a clue to a low voltage problem.

 

[D.A.(Tony)Stewart]

Yup, did Memtest, hdd test, even BIOS diagnostics from Dell. All fine. It is clearly something that can't be detected in software, but can't figure out what. I don't even have known test points to measure voltages or something on the board.

If it runs all night on Memtest86+ ok but still fails at random within seconds, there may be other clues we need to know, historically how often this started and when and if possibly related to software or driver changes.

I would ask you to run (Win+r) msinfo32 (Enter) then save the result like wmm.nfo then rename the suffix or add .zip so it can be uploaded to this server and then I can look at crash log entries , running software etc.

 

[vvmm]

@SunnySkyguy: I used windows memory diagnostic tool and, if I find a right time when it doesn't shut off, it passes the test, so I certainly would say that based on the tests, the RAM modules are not bad.
I do not think that any driver in the world can be the culprit here, as I said that sometimes the laptop does not power on at all, only after a few tries or minutes passed.
For the moment, I tried starting windows again several times, but have not managed to make it after the logon password prompt.

@BradtheRad: I will try to measure voltage and current of power supply and/or power rails to see if there is any change in the moment of failure, maybe this can lead to a faulty dc-dc converter of some kind, but it would then be hard to identify.