Amilo M1425 Notebook repair - how to locate root cause on shorted DC input?

[carl_lab]

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?

[Tony.T]

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.

[carl_lab]

Thanks, Tony.
Freezing spray could do it because I have no thermal imager.
Hoping nothing else melts down... 

[Monkeh]

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..

[carl_lab]

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.

[Richard Crowley]

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.

[carl_lab]

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...

[Monkeh]

https://elektrotanya.com/uniwill_255_259iax_rev_c_sch.pdf/download.html

That took all of 3 minutes.

[dicky96]

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

[GamerAndds]

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?

[Rasz]

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

[carl_lab]

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... 

[Monkeh]

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.

[carl_lab]

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)

[Monkeh]

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.

[carl_lab]

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.

[carl_lab]

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! 

Don't say thanks or anything.

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

[carl_lab]

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)

[ElektroQuark]

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.

[P90]

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.

[carl_lab]

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...

[Rasz]

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

[dicky96]

@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

[Richard Crowley]

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).

[carl_lab]

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...

[dicky96]

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.

No I meant with PL2 removed and drive the load direct from a bench PSU with CC mode.  If you drive it from the 19V side you are making the buck regulator on that rail drive intro a (nearly) short circuit.  It won't like that.

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 (PQ49) !



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 (PQ49) and try to get replacement...

Ah I should have explained more the idea of this fault finding technique. It wasn't that I thought that the fault was heat sensitive.  When a component fails and goes low resistance it often becomes very thermally unstable as well - so heating and  or cooling can have a noticeable effect on the resistance of the faulty component if you monitor the resistance of the 'short' and your DMM is sensitive enough to read .1 or even .01 ohm resolution 

The s/c mosfet is an interesting find.  Does the short circuit from PL1 or PL2 inductors go away with the mosfet removed?

Regards a GPU getting warm in normal operation - yes it would.  But that is with the GPU being clocked at high frequencies which is most likely not the case at all with your current s/c fault on at least 2 voltage rails. And heating the other semiconductors didn't have much effect 

The fact it reacts to you warming it seems more likely to indicate this is where your short is.  If you are saying the s/c mosfet is related in some way to a 1.2V voltage rail which supplies te GPU and is too high (which could be the case if the mosfet was supposed to be regulating that rail) it is possible you have a s/c mosfet and a faulty GPU because of that. 

The short reacting to external heating specifically when you heat the GPU and the fact the GPU is the thing generating heat proportional to the amount of current when you feed into the voltage rail from your bench psu tell us quite a lot I think.  Having said all this I am not in anyway an expert on motherboard repair, in fact I am a learner.  I just have lot of experience on electronics repair techniques in general.

Rich

[carl_lab]

No I meant with PL2 removed and drive the load direct from a bench PSU with CC mode.  If you drive it from the 19V side you are making the buck regulator on that rail drive intro a (nearly) short circuit.  It won't like that.

I don't see a significant difference with or without PL2 populated.

I unplugged original 19V-PS and injected voltage from laboratory PS at the solder joints of the jack.
No problem at all. I set I=1A (later 1.5A) max and V=2.5V, so I found GPU is warming.



Then I measured voltage at GPU (1.85V) and found out, from which rail it comes (PL12, normally 1.2V).
I removed PL12 and injected 1.2V at load side. I = 450 to 500mA so I think (hope), GPU is not shorted.

Does the short circuit from PL1 or PL2 inductors go away with the mosfet removed?

There was no real short.
Shorted MOSFET is removed now, and I'm looking for a replacement.

I'm not quite sure, if I should operate the PCB without replaced MOSFET for testing, maybe it's not a good idea to switch it on, without 1.2V supply (GPU and more?)...

[dicky96]

Ahh  I see on the schematic  PL2 is not part of a buck regulator circuit.  It is an input filter inductor or something like that on the 19V rail.  I agree it makes no difference whether you power using the bench supply from the DC jack or PL2.  Sorry I didn't look before. 

PL12 is part of a buck regulator however.

I would certainly replace the MosFET first :-)  Where is PQ49 on the schematic?

Rich

[carl_lab]

Where is PQ49 on the schematic?

[dicky96]

Cheers mate that explains why I couldn't find it.  You mis-typed PQ49 not PQ59 

That isn't good is it, for anything that was on the 1.2V rail. A drain-source short on PQ59 is going to connect Vin directly to the 1.2V rail so 19V is likely to go to where it shouldn't. Until of course the PSU trips out or whatever.

This is also a good example why you shouldn't power the 19V with your bench supply to see what gets hot on the lower voltage rails. You should power the short circuit rail directly with the inductor removed and your bench supply set for the maximum voltage of that rail. Which was my original posts suggestion.  Having said that you already had a low resistance on this rail before you started powering with the bench supply so any damage done was already done.

So even before you change the s/c FET PQ59 you need to find out why you have a 5.1 ohm low resistance on the load side of PL12 other wise you will quite likely just blow the replacement FET anyway.  If you still have 5.1ohm on PL12 that is. I assume you still do?

I would connect a lab supply to the load side of PL12 set to 1.2V maximum and with current limit on.  Then wind up the current and see what gets hot - but from various observations so far it is going to be the GPU. The schematic says this 1.2V 7A rail is the VGA supply.

Alternatively you could try my trick of warming and cooling the GPU and at the same time measure resistance PL12 load side to ground.  If you have a sensitive DMM and can read 0.01ohm or 0.1ohm increments and the resistance changes when you warm the GPU that is another good indicator you have located the underlying problem. 

What part number is the GPU anyway? Is it a BGA package, or something more easily workable?

Rich

[Rasz]

5.1 ohm low resistance 
this 1.2V 7A rail

why do you think 5 ohm is low resistance on this(10W gpu) rail?

[carl_lab]

Cheers mate that explains why I couldn't find it.  You mis-typed PQ49 not PQ59 

Sorry...

Having said that you already had a low resistance on this rail before you started powering with the bench supply so any damage done was already done.
So even before you change the s/c FET PQ59 you need to find out why you have a 5.1 ohm low resistance on the load side of PL12 other wise you will quite likely just blow the replacement FET anyway.
If you still have 5.1ohm on PL12 that is. I assume you still do?

I measured now 6.5 Ohm, what is not excessively low for a 1.2V/7A rail.

I=U/R=1.2V/6.5Ohm=185mA, or in other words 2.6% of full amperage.
The MOSFET (4404) is able to drive 23A.

So I hope, hickup protection mode of original DC adapter prevented a real short to GND.
I just measured a few ms-short 5V pulses at DC-in, repeated every few 10ms. 

I would connect a lab supply to the load side of PL12 set to 1.2V maximum and with current limit on.  Then wind up the current and see what gets hot - but from various observations so far it is going to be the GPU. The schematic says this 1.2V 7A rail is the VGA supply.

That's exactly, what I did already:

I unplugged original 19V-PS and injected voltage from laboratory PS at the solder joints of the jack.
No problem at all. I set I=1A (later 1.5A) max and V=2.5V, so I found GPU is warming.

Then I measured voltage at GPU (1.85V) and found out, from which rail it comes (PL12, normally 1.2V).
I removed PL12 and injected 1.2V at load side. I = 450 to 500mA so I think (hope), GPU is not shorted.

I forget to add: GPU stays cool at 1.2V/500mA.

What part number is the GPU anyway? Is it a BGA package, or something more easily workable?

It's an ATI Mobility Radeon 9700. BGA, about 30mm x 30mm size.

[dicky96]

why do you think 5 ohm is low resistance on this(10W gpu) rail?

@rasz
Because carl_lab is measuring with a DMM on resistance range so that should not even turn on semiconductor junctions in the GPU, plus the GPU only draws a lot of current when it is working at high frequencies.

5 ohm on a DC resistance test seems very low to me.  But as I mentioned earlier I am no expert on motherboard repairs so I could be wrong.

@carl_lab
As you also said you have low resistance on Vcore it is probably worth checking high side FETs PQ2 and PQ4 for short circuits as well


Rich

[carl_lab]

...probably worth checking high side FETs PQ2 and PQ4 for short circuits as well

They seem to be OK.

[carl_lab]

Today I got the MOSET(s). I soldered one in and injected voltage at the 19V DC in (rising slowly from 1V to about 16V). Below 10V current was very low, but then rised up to 1A @ 16V). Suddenly smoke came from the backside of PCB.
I switched off and found a cracked PU10 = ISL6224CB (SMPS controller of 1.2V rail) that released the magic smoke.



Tried to order a few ISL6224 but they seem to be obsolete and not available anymore.
Intersil named ISL6269 as replacement, but wrong casing (QFN 4x4 instead of needed SSOP-16).

Found some ISL6224 on ebay.
Waiting again...

[Rasz]

PU10 was already damaged?
your replacement PQ59 was DG shorted?
you soldered it in wrong orientation?

even diagram is wrong ;] look at the arrows on PQ58/59, its picasso FET, someone knew all the parts, just didnt know the order?

why do you think 5 ohm is low resistance on this(10W gpu) rail?

@rasz
Because carl_lab is measuring with a DMM on resistance range so that should not even turn on semiconductor junctions in the GPU, plus the GPU only draws a lot of current when it is working at high frequencies.

5 ohm on a DC resistance test seems very low to me.  But as I mentioned earlier I am no expert on motherboard repairs so I could be wrong.

its best to experiment, take any graphic card and measure vGPU rail, it will be <1ohm on modern 100W chips.

[carl_lab]

PU10 was already damaged?

Probably it was.

your replacement PQ59 was DG shorted?

No.

you soldered it in wrong orientation?

No.

[Rasz]

recheck PQ58/59 and PD11 for shorts just in case

[carl_lab]

recheck PQ58/59 and PD11 for shorts just in case

I have removed the broken controller IC and PL12 to re-check following components:

PD9+11:
reverse direction: high-impedance
forward voltage: 0.2 V -> OK (schottky)

PQ58+59:
Rgs: high impedance
Rds: ~40 kOhm (in-circuit), reverse voltage 0.5 V (body diode)
Rdson: <0.1 Ohm @Vgs = 5 V -> OK

PR70: 1.5k Ohm (OK)
PC56: 100 nF (OK)

Resistance (load side) 1.2V rail to GND: ~6 Ohm (OK)

So everything should be OK.

Still waiting for some chinese electronic parts...