Author Topic: Amilo M1425 Notebook repair - how to locate root cause on shorted DC input?  (Read 8610 times)

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Offline carl_lab

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Notebook can not be switched on, DC input is pulsing (hickup), so probably something inside is shorted/overcurrent.
DC supply is OK, works on another notebook. Resistance at notebook's DC in jack is about 750 Ohms between + and -.
Could not find any suspicious component by optical inspection of PCB.
Checked a few fuses inside, no problem found.

I don't know exactly what happened but I assume reversed DC polarity or overvoltage.
Unfortunately I couldn't find schematics of this notebook (Fujitsu Amilo M1425).
Is there a chance to repair?

« Last Edit: June 01, 2017, 09:29:13 pm by carl_lab »
 

Offline Tony.T

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #1 on: June 01, 2017, 09:14:53 am »
Heat camera....freezing spray...or just using the hand.
Put in some lower voltage via a adjustable power supply and you could see where it starts to get hot first.

Using freezing spray will point you where it melts first.  Camera will show you as well. With hand it could be harder.
 
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Offline carl_lab

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #2 on: June 01, 2017, 12:46:24 pm »
Thanks, Tony.
Freezing spray could do it because I have no thermal imager.
Hoping nothing else melts down...  ;)
 

Offline Monkeh

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #3 on: June 01, 2017, 12:47:30 pm »
Unfortunately I couldn't find schematics of this notebook (Fujitsu Amilo...).

If you were to fill in the '...' someone might be able to find them for you..
 

Offline carl_lab

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #4 on: June 01, 2017, 01:25:22 pm »
Unfortunately I couldn't find schematics of this notebook (Fujitsu Amilo...).

If you were to fill in the '...' someone might be able to find them for you..
Of course I will do, when I'm at home again.  ;)

PS: It's an Amilo M1425.
« Last Edit: June 01, 2017, 04:03:02 pm by carl_lab »
 

Offline Richard Crowley

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #5 on: June 01, 2017, 01:49:30 pm »
There is a whole YouTube channel essentially focused on your question.  Highly recommended...

https://www.youtube.com/user/rossmanngroup

Louis Rossman has done perhaps hundreds of videos on identifying faulty (often dead-short) components on a motherboard.  He uses mostly the technique mentioned by @carl_lab and demonstrates that technique on-screen.

There are apparently black-market sources for service information for many consumer products like notebook PCs of various brands. But I have no direct experience with how to find them.

 
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Offline carl_lab

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #6 on: June 01, 2017, 06:00:33 pm »
There is a whole YouTube channel essentially focused on your question.  Highly recommended...

https://www.youtube.com/user/rossmanngroup
Watched 2 or 3 of his videos. Temperature method (feeling with fingers, evaporating alcohol or freezing spray) seem to be promising.
So I probably go that way.

But that guy seem to be very "special".
Very rude in talking and acting on PCB. Lots of flux, lots of solder, lots of superfluous words, lots of swearing like a trooper.
His methods seem to work, but I definitely would not give him anything to repair...
« Last Edit: June 01, 2017, 07:11:06 pm by carl_lab »
 

Offline Monkeh

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Offline dicky96

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #8 on: June 01, 2017, 06:25:24 pm »
carl_lab
What you will find, if there is a short circuit, but you are reading 750 ohms on the DC input, is that the short is on one of the lower voltage rails that are generated from the 19V? DC input.

If you do not have a schematic, look for some inductors which will be near to buck regulator type chips. There will probably be several of these circuits for 12V, 5V, 3.3V and maybe 1.6V

They will probably look something like the components marked 3R6 and the chip marked 1597A on the left side of the attached photo.  You may be lucky and some voltages may also be silk screened on the board.  This is not a motherboard but it gives some idea what a buck regulator circuit looks like physically.

Measure the DC resistance from these inductors to ground and you will probably find which rail has the short on it.

Then it is a matter of removing the inductor on the bad rail and looking to see if the short is on the supply side or load side.  If it is on the supply side it is almost certain the be the buck regulator chip itself.  If it is on the load side then the best way would be to power that voltage rail off a bench supply with current limit and wind up the current until something gets hot.  The only problem with this is that it helps to know the working voltage of the short circuit rail.

There are a huge number of schematics for laptops notebooks etc on badcaps.net forum in the 'Troubleshooting laptops, portable and mobile devices' section  ;)

Hope that helps
Rich
« Last Edit: June 01, 2017, 06:26:57 pm by dicky96 »
 

Offline GamerAndds

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #9 on: June 01, 2017, 06:45:06 pm »
There is a whole YouTube channel essentially focused on your question.  Highly recommended...

https://www.youtube.com/user/rossmanngroup
Watched 2 or 3 of his videos. Temperature method (feeling with fingers, evaporating alcohol or freezing spray) seem to be promising.
So I probably go that way.

But that guy seem to be very "special".
Very rude in talking and acting on PCB. Lots of flux, lots of solder, lots of superfluous word, lots of swearing like a trooper.
His methods seem to work, but I definitely would not give him anything to repair...

Ill agree with your last statement there... I honestly dislike him.

I had a dell XPS 13 that had a faulty DC power problem and could never find out what was wrong with it. When power was applied to it an inductor got really REALLY hot. My personal suspicion is still to do with the battery charge circuit, since it is always active- that is, whether the laptop is on or off the battery charging circuit always get juice. Perhaps this will narrow down your search?
 

Offline Rasz

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #10 on: June 01, 2017, 07:59:09 pm »
But that guy seem to be very "special".
Very rude in talking and acting on PCB. Lots of flux, lots of solder, lots of superfluous words, lots of swearing like a trooper.
His methods seem to work, but I definitely would not give him anything to repair...


and yet here you are, unable to even google "Fujitsu Amilo M1425 diagram" on your own, who is special exactly here?   :-//

basics:
https://translate.google.com/translate?hl=en&sl=pl&u=https://www.elvikom.pl/szkolenie-nr-1-podstawy-diagnostyki-plyt-glownych-laptopow-t986.html
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Offline carl_lab

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Offline Monkeh

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #12 on: June 01, 2017, 08:51:00 pm »
https://elektrotanya.com/uniwill_255_259iax_rev_c_sch.pdf/download.html

That took all of 3 minutes.
What does this mean, I don't get it...  :-//

Unfortunately I couldn't find schematics of this notebook (Fujitsu Amilo M1425).

Here's your schematics.
 

Offline carl_lab

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #13 on: June 01, 2017, 09:03:46 pm »
basics:
https://translate.google.com/translate?hl=en&sl=pl&u=https://www.elvikom.pl/szkolenie-nr-1-podstawy-diagnostyki-plyt-glownych-laptopow-t986.html

Thank you!

and yet here you are, unable to even google "Fujitsu Amilo M1425 diagram" on your own, who is special exactly here?   :-//

You are wrong, if you think I did not google that. I also googled combinations with "service manual", "schematic" etc.
No usable findings (see posting #1 of this thread).

Can you please link your successul search to that specific schematic you are referring?

(Schematics linked by Monkeh)
« Last Edit: June 01, 2017, 09:25:45 pm by carl_lab »
 

Offline Monkeh

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #14 on: June 01, 2017, 09:10:20 pm »
Searching for a schematic leads to reference of buying one, and identifies the board (as a Uniwill 255/259.. also printed ON THE BOARD!). Searching for that finds.. a schematic. Which I linked. Don't say thanks or anything.

There is not always a simple single step solution, you must work at it.
 

Offline carl_lab

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #15 on: June 01, 2017, 09:13:40 pm »
If you do not have a schematic, look for some inductors which will be near to buck regulator type chips. There will probably be several of these circuits for 12V, 5V, 3.3V and maybe 1.6V

They will probably look something like the components marked 3R6 and the chip marked 1597A on the left side of the attached photo.  You may be lucky and some voltages may also be silk screened on the board.  This is not a motherboard but it gives some idea what a buck regulator circuit looks like physically.

Measure the DC resistance from these inductors to ground and you will probably find which rail has the short on it.

Then it is a matter of removing the inductor on the bad rail and looking to see if the short is on the supply side or load side.
Thank you!
I will try the way you described.
I disassembled the notebook to remove the main pcb completely to get access to both sides.
 

Offline carl_lab

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #16 on: June 01, 2017, 09:24:23 pm »
Searching for a schematic leads to reference of buying one, and identifies the board (as a Uniwill 255/259.. also printed ON THE BOARD!). Searching for that finds.. a schematic. Which I linked.

Oh, I see, the 255/259 silk screen imprint was covered by installed RAM modules!  :palm:

Don't say thanks or anything.

I'd have thanked you very much, but if you prefer not to be thanked, I do not...   :popcorn:
 

Offline carl_lab

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As dicky96 recommended I measured resistance of those SMPS inductors against GND:
PL12: 5.1 Ohm (+V1.2/7A rail)
PL1: 8.2 Ohm (Vcore/25A rail)   
(other inductors against GND: much more ohms)

« Last Edit: June 02, 2017, 07:57:05 am by carl_lab »
 

Offline ElektroQuark

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I repaired an Amilo for a friend. Similar symptoms. His daughter pushed on an USB stick in the wrong way, so the USB socket was destroyed and connector has +5 and GND lines shorted. I cut the pins out and the short disappeared, so the laptop worked again.
Sometimes the fixes are that simple.

Offline P90

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Re: Notebook repair - how to locate root cause on shorted DC input?
« Reply #19 on: June 02, 2017, 07:33:41 am »
There is a whole YouTube channel essentially focused on your question.  Highly recommended...

https://www.youtube.com/user/rossmanngroup
Watched 2 or 3 of his videos. Temperature method (feeling with fingers, evaporating alcohol or freezing spray) seem to be promising.
So I probably go that way.


But that guy seem to be very "special".
Very rude in talking and acting on PCB. Lots of flux, lots of solder, lots of superfluous words, lots of swearing like a trooper.
His methods seem to work, but I definitely would not give him anything to repair...
[/b]
Yes, I can't stand to watch his videos. He seems very condescending and full of himself. He is rude and obnoxious.
 

Offline carl_lab

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Quote
PL1: 8.2 Ohm (Vcore/25A rail) to GND

I removed PL1 and found 8.2 ohm load at CPU side.
Want to take CPU out of socket but it is very stubborn (yes, I opened locking mechanism before).



The opening mechanism don't turn the full 90° angle, just about 45°.
The light blue slider becomes a little loose, but CPU is still firm in socket.
I don't wanna break it...
« Last Edit: June 02, 2017, 09:30:16 am by carl_lab »
 

Offline Rasz

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and you think 150mA is bad because?
http://www.ohmslawcalculator.com/ohms-law-calculator
read the basics link I gave you
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Offline dicky96

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@carl_lab
If it doesn't want to come out of hte socket, try heating the CPU with a hair dryer, or freezing it, and see if the resistance from the PL1 inductor to ground changes.  Without heating or cooling other components if possible.  Do this with your DMM set on the lowest ohms range it has.  If you don't see any change in resistance try heating or cooling the whole board and try to narrow down the area which makes the resistance change the most (assuming it does change)

Have you removed the PL2 inductor yet?  If you have one, you could try a bench power supply on load side of PL2 to ground.  Set it for 1.2V and CC mode then send an amp or so down the voltage rail and see if anything warms up.  You may have to increase the current to a few amps

You could also try this on the Vcore rail with PL1 removed but I don't know what max voltage that should be - can someone educate me here please?

Regards Louis Rossman videos,  Contrary to other opinion - I actually like the guy, he clearly knows what he is doing and he makes me laugh

Richard
« Last Edit: June 02, 2017, 02:43:00 pm by dicky96 »
 

Offline Richard Crowley

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Regards Louis Rossman videos,  Contrary to other opinion - I actually like the guy, he clearly knows what he is doing and he makes me laugh
I agree completely.  He is very smart, efficient, cost-effective, entertaining, informative, and has low tolerance for fools.  I would take my broken gadget to him in a New-York second.  (If I lived in New York City).
 

Offline carl_lab

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and you think 150mA is bad because?

No, I just wanted to find the highest loads and if it is on the "right" side of the inductors (to find shorted switching MOSFETS).
I also wanted to inject external voltage, eventually.

You could also try this on the Vcore rail with PL1 removed but I don't know what max voltage that should be - can someone educate me here please?

Googled CPU type: SL7EN, RH80536 1800/2M -> Pentium M 745,  1.276–1.34 V.

Have you removed the PL2 inductor yet?  If you have one, you could try a bench power supply on load side of PL2 to ground.  Set it for 1.2V and CC mode then send an amp or so down the voltage rail and see if anything warms up.  You may have to increase the current to a few amps.

You are talking about 19V rail (PL2 is still in place)?
I injected 2,5V @19V rail (DC-in), current is 1.5A.
GPU is getting warm. On higher voltage/current it's getting warmer (and faster), so I did this only for a few seconds.
I know, it's getting warm at normal operation, but I don't know how far can I go with removed heat sink.

@carl_lab
If it doesn't want to come out of hte socket, try heating the CPU with a hair dryer, or freezing it, and see if the resistance from the PL1 inductor to ground changes.  Without heating or cooling other components if possible.  Do this with your DMM set on the lowest ohms range it has.  If you don't see any change in resistance try heating or cooling the whole board and try to narrow down the area which makes the resistance change the most (assuming it does change).

I heated CPU, GPU and the third "CPU-like" (bridge?) IC using a heat gun (not too hot, ~60-70°C):
The only one that showed a reaction was GPU (currrent increase from 1.5 to 1.8A @Vin=2.5V ).
I think changing load over temperature would be relative normal (it's a semiconductor).
I also think the problem is a permanent one, not a temperature problem.

GPU supply, I measured at one of the bigger ceramic caps at the backside of the GPU, is about 1.85V @Vin=2.5V (2.1V @Vin=3.0V).
That's the same voltages (1.85V, 2.1V) I can measure at PL12.
That's 1.2V rail, the voltage is to high.

Found shorted high-side switching MOSFET (PQ59) !




Removed PL12 to inject 1.2V from external supply.
Current is 450-500mA. GPU stays cool, so I hope, it's not damaged.

I will remove MOSFET (PQ59) and try to get replacement...


« Last Edit: June 03, 2017, 05:23:00 pm by carl_lab »
 


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