jfm
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The harder you're scratching your head, the harder the mobo is laughing at you 
Samsung Notebook "no power"
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NviGate Systems
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More than likely a surface mount transistor/mosfet/coil has failed. When you let it cool down then turn it on, it works but as soon as the temperature reaches a certain limit, it throttles the power or simply drops the voltage which in turn has a cascade effect on the rest of the system components who are relying on this rail for power. If you run the laptop with a fan pointing at the MB you may find it stays powered on if that is the case.
Most board failures are a simple component that provides power or smooths power for a circuit. Once those components have been replaced usually the system is fine. But what can you expect for 2 cents parts? Spend 10 cents and get something with twice the life.
Most board failures are a simple component that provides power or smooths power for a circuit. Once those components have been replaced usually the system is fine. But what can you expect for 2 cents parts? Spend 10 cents and get something with twice the life.
I've informed the customer about this, and she agreed that it's not worth replacing the board. She also wants to purchase another laptop, since she's been replacing parts on this one quite a lot recently.
As a good customer, I'll be refunding her for the replaced screen a few weeks ago (which is still covered by warranty in any case), so she's a happy customer.
@NviGate Systems, would you say it's still possible to repair the board? If yes, I can actually check with the client if I can get hold of the laptop. That way I'll be able to try and read the schematics and maybe find my way to the failing part. What's your opinion about this?
As a good customer, I'll be refunding her for the replaced screen a few weeks ago (which is still covered by warranty in any case), so she's a happy customer.
@NviGate Systems, would you say it's still possible to repair the board? If yes, I can actually check with the client if I can get hold of the laptop. That way I'll be able to try and read the schematics and maybe find my way to the failing part. What's your opinion about this?
NviGate Systems
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It depends if it's a simple component or not. I can't recall the name (I am slowly teaching myself and learning about these circuits) but these chips have a gate, drain and source. They have three leads. Never mind, I cheated. MOSFET.
They are responsible for switching voltages, amplifying etc. On many TV sets Mosfets are responsible for no power. The circuits are similar in the sense of switch mode PSU then a DC to DC circuit.
The trouble is many of the Mosfets are so tiny, you need a schematic to know proper values as it might not be labelled.
After Mosfets are Tantalum Capacitors. Well, most caps really.
In basic circuit, Caps, Mosfets, Transistor and coils. The surface mount type are tiny, never tested them.
If you have a thermal camera or a laser guided thermal gun you can narrow down areas that overheat prior to shutdown to try and pinpoint quicker if it's a heat failure. (The reasoning behind this is failing electronics often have very low efficiency ratings, hence will generate more wasted energy/heat which can often trigger fail safes to prevent catastrophic failures.)
They are responsible for switching voltages, amplifying etc. On many TV sets Mosfets are responsible for no power. The circuits are similar in the sense of switch mode PSU then a DC to DC circuit.
The trouble is many of the Mosfets are so tiny, you need a schematic to know proper values as it might not be labelled.
After Mosfets are Tantalum Capacitors. Well, most caps really.
In basic circuit, Caps, Mosfets, Transistor and coils. The surface mount type are tiny, never tested them.
If you have a thermal camera or a laser guided thermal gun you can narrow down areas that overheat prior to shutdown to try and pinpoint quicker if it's a heat failure. (The reasoning behind this is failing electronics often have very low efficiency ratings, hence will generate more wasted energy/heat which can often trigger fail safes to prevent catastrophic failures.)
Thanks for the info, watched some videos about them too. Yes, I can see them being so small, as a problem. I'll try to get hold of this laptop and maybe start with investing in a tool that can measure the temperature.
I'll keep updating this thread, so those who are interested in doing the same, can follow us and learn at the same time.
Do you have a thermal camera or a leaser guided thermal gun yourself? If yes, do you recommend any in particular?
I'll keep updating this thread, so those who are interested in doing the same, can follow us and learn at the same time.
Do you have a thermal camera or a leaser guided thermal gun yourself? If yes, do you recommend any in particular?
Larry Sabo
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A FLIR One is only $240 USD. It's a smartphone add-on. If I did more component-level repairs I'd be bugging Santa for one of these.
FLIR seems to be the name for thermal cameras. Seen the most expensive ones, wow That phone one is also good for a basic thermal camera, I might try to get hold of one as a self gift (cause I obviously don't do much component level repairs).
In the meantime, I borrowed a laser guided thermal thermometer. The disadvantage of these is clear, you have to focus on a particular spot to know the temperature, since you don't get an image of an area. That makes finding the components that are heating up, very difficult.
That phone one is also good for a basic thermal camera, I might try to get hold of one as a self gift (cause I obviously don't do much component level repairs).In the meantime, I borrowed a laser guided thermal thermometer. The disadvantage of these is clear, you have to focus on a particular spot to know the temperature, since you don't get an image of an area. That makes finding the components that are heating up, very difficult.
Larry Sabo
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The other thing with laser thermometers is, they greatly depend upon the emissivity of the object to be measured. I have one and have never found it to be as accurate as a good thermocouple but sometimes you just can't use a T/C. I was surprised recently when I checked the controller accuracy of a new pre-heater I had bought -- the laser thermometer appeared to be bang-on based on the solder melting temp of 183C. I was aiming it at an IC on a PCB laid on the pre-heater and the IC had a nice black surface (high emissivity).
So Mosfets, can be used to lower the voltage? Lets say, from 15V to 3V?
It's another laptop, but I'm checking the voltage that's going through the rails, and at one particular mosfet, the voltage drops from 15V to around 3V. Now, since I'm a noob in this subject... does it make sense?
This is the schematic, and the laptop is not even powering on (confirmed that power is getting through the DC Jack fine - 100%):
http://www.smdcode.com/media/service-manuals/laptops/gateway/compal-la-6901p-r01-schematics.pdf
Page 47 (voltage at PQ7 is 15V then voltage at PQ5 drops to 3V).
It's another laptop, but I'm checking the voltage that's going through the rails, and at one particular mosfet, the voltage drops from 15V to around 3V. Now, since I'm a noob in this subject... does it make sense?
This is the schematic, and the laptop is not even powering on (confirmed that power is getting through the DC Jack fine - 100%):
http://www.smdcode.com/media/service-manuals/laptops/gateway/compal-la-6901p-r01-schematics.pdf
Page 47 (voltage at PQ7 is 15V then voltage at PQ5 drops to 3V).
NviGate Systems
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Keep in mind I'm new at this stuff when it comes to reading schematics, but I have watched a few of Rossman's repair videos that I sorta know what to look for.
There are two voltage sources here, one from the dc in (adapter) and one from battery + terminal.
It looks like PQ7 goes to PR14, which in turn goes to PL22, as the name on the schematic shows, this is part of the pre-charge circuit, as some of the voltage goes for charging battery. Some also goes to the CMOS battery which may be re-chargable.
You can google the part # for each of the Mosfets ie; AO4407A, which will take you to a few sites where they list specs, although it's possible there could be multiple versions all rated differently.
There are two voltage sources here, one from the dc in (adapter) and one from battery + terminal.
It looks like PQ7 goes to PR14, which in turn goes to PL22, as the name on the schematic shows, this is part of the pre-charge circuit, as some of the voltage goes for charging battery. Some also goes to the CMOS battery which may be re-chargable.
You can google the part # for each of the Mosfets ie; AO4407A, which will take you to a few sites where they list specs, although it's possible there could be multiple versions all rated differently.
I'm watching Rossman's videos too. So far, they are over complicated to me, however very interesting.
So you're saying... that you have an input of 15V, that is distributed into:
- PL22 to CHG_B+ (do you know what CHG_B+ is?)
- PQ5 (that I'm assuming goes to charge the battery)
So... am I right to say, that low voltage on PQ5 is possible? And then, do you have any idea why when I measure the voltage coming out to the battery pinouts drops to 0.6V?
So you're saying... that you have an input of 15V, that is distributed into:
- PL22 to CHG_B+ (do you know what CHG_B+ is?)
- PQ5 (that I'm assuming goes to charge the battery)
So... am I right to say, that low voltage on PQ5 is possible? And then, do you have any idea why when I measure the voltage coming out to the battery pinouts drops to 0.6V?
Larry Sabo
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I forget all this stuff but basically, B+ is the supply to other power circuits of the laptop and is fed from either VIN, BATT+ or a balance between them, depending on whether the laptop is operating only on AC, battery or both. Here's a good YouTube video on testing the DC charging circuit of a laptop motherboard. Here's another on diagnosing a dead motherboard that's very good, if you can get past the language barrier. I would suggest subscribing to Sieguntar's YouTube channel as he has a ton of such useful videos.
Hi Larry, you're always coming to the rescue
Yes, the B+ (and other +'s) almost all have the a page number written next to them. Then you can go to that particular page and find the details of that circuit. This makes more sense now.
That video is excellent.
A tip to those who are looking into trying this... if possible, try to also find the Board View along with the schematics. This is an interactive board view that can search and tell you were the components are and to which circuitry they are connected to. It gives you all the details and more.
Yes, the B+ (and other +'s) almost all have the a page number written next to them. Then you can go to that particular page and find the details of that circuit. This makes more sense now.
That video is excellent.
A tip to those who are looking into trying this... if possible, try to also find the Board View along with the schematics. This is an interactive board view that can search and tell you were the components are and to which circuitry they are connected to. It gives you all the details and more.
Hey guys, believe it or not, I'm hopeful that I found the issue.
If you had to access the link (from 2 posts ago), I traced the voltage from the DC Jack till something was strange. I ended up on PD2 (look it up), which is a LL-34 switching diode. The voltage input on this diode is 15V and the output is 0.68V. Skipping the rest... I checked the voltage that is coming out to the battery and found out that the pins of the battery charger is also outputting 0.68V. Now, as far as I know, this should be 3.3V or 5V.
I don't know if this makes sense. Maybe someone can tell
http://www.rectron.com/data_sheets/ll4148.pdf
If you had to access the link (from 2 posts ago), I traced the voltage from the DC Jack till something was strange. I ended up on PD2 (look it up), which is a LL-34 switching diode. The voltage input on this diode is 15V and the output is 0.68V. Skipping the rest... I checked the voltage that is coming out to the battery and found out that the pins of the battery charger is also outputting 0.68V. Now, as far as I know, this should be 3.3V or 5V.
I don't know if this makes sense. Maybe someone can tell
http://www.rectron.com/data_sheets/ll4148.pdf
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NJW
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It's just a diode – 'fast switching' is its characteristic. I suspect it's just a SMD version of the ubiquitous 1N4148 and is there to prevent backflow to the battery ('BATT+'). PD1 performs a similar function on 'VIN'.
These are low current diodes (Forward current = 300 mA), so they don't carry power, rather they are isolators for the lines sensing the voltage on 'BATT+' and 'VIN', respectively.
There isn't really an input or output – better to give the voltage on the cathode (the line end of the symbol) and anode.
Note: no deep analysis involved here, just informed guesswork.
(Edited for typo.)
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Thanks a lot for the info
Somehow I managed to replace the diode and now there is voltage on the battery's connector. Having said that, still no power haha
I am however stuck at PU1 (charger controller), just because I don't know how to test that.
http://pdf1.alldatasheet.com/datasheet-pdf/view/120201/INTERSIL/ISL6251AHAZ-T.html
No voltage seems to be running to the other circuits. Also, this PU1 seems to be very hot.
Pg.47: http://www.smdcode.com/media/service-manuals/laptops/gateway/compal-la-6901p-r01-schematics.pdf
Somehow I managed to replace the diode and now there is voltage on the battery's connector. Having said that, still no power haha
I am however stuck at PU1 (charger controller), just because I don't know how to test that.
http://pdf1.alldatasheet.com/datasheet-pdf/view/120201/INTERSIL/ISL6251AHAZ-T.html
No voltage seems to be running to the other circuits. Also, this PU1 seems to be very hot.
Pg.47: http://www.smdcode.com/media/service-manuals/laptops/gateway/compal-la-6901p-r01-schematics.pdf
Larry Sabo
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Charging controllers fail fairly often. It might be worth changing it, if you're comfortable doing so.
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