ASUS u31sd LAPTOP WILL NOT TURN ON

[sasser]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Everytime im face with this problem what i do is pull out all component like lcd cable. Dvd rom ram processor, connector power jack and wifi card. The assamble back. Hold power button for 20-30second. The release and start your laptop. Mostly u will get back your system up. In my case volt need 19.0 4.34a. But my regulator power supply give more than current and system got no display

[CR Designs]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Need help testing laptop

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Need help testing laptop

sorry i am a busy person not available 24-7 i repair laptops and other computers for a living and i got swamped with work....

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Here is the data sheet on the larger square ic i have a feeling this is most likely your problem , will require a reflow or a IR station to remove this ic....the whole bottom is a ground pad ..... but lets test that 8 pin mosfet first and do some tests...

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

okay on the 8 pin fet you want to locate pin#1 that is source and put a probe there and on the opposite side of ic is drain all 4 of them usually and put dmm on continuity and check for shorts if it shows short desoilder it and retest on bench

if it still shows short between source and drain then its bad and let us know so we can find you a replacement i am having some difficulties on finding the data sheet on given part # however i am certain this fet is ok because it does turn on if it was bad most likely it would do nothing since it is primary on the dc input...

the bigger ic is another form of voltage regulation and it can be configured to have 3 outputs and if any of the 3 is bad something is not gonna get power and the rest will.... i am betting in theory not 100% but certain enough this ic may get hot due to having a problem ..

clean the heat sink of old thermal grease and reapply new and ever so carefully make sure the thermal pads are applied where it came from and clean you can clean the pads with q tip and rubbing alcohol very carefully..and reinstall the sink and power this thing up and let me know if the ISL95831HRTZ gets unusually warm or hot.. if it does most likely its bad due to internal short....


you can test the outputs on it with the provided datasheet and see if there is missing outputs remember to use neg probe on the motherboards screw holes where it is copper as ground reference and positive on the output pins be careful not to slip and steady hands....if the head of your probe is too big you may file it down or soldier sewing needle to the probes to get it in there safely to do the test... hope its not over volting but still have a hard time believing phone charger could damage anything most are 5 volts for cell phones was it a cell phone charger or land line phone charger? i hope you tried the reset correctly.... Lemmie know..

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

any results?

[CR Designs]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Not yet we had a medical emergency today . What fet are you referring to? can you show on picture. I'm new at working on motherboards. I swap out boards not repair.

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Not yet we had a medical emergency today . What fet are you referring to? can you show on picture. I'm new at working on motherboards. I swap out boards not repair.

sorry to hear hope all is well,,,,the 2 ic's you marked for me with the part numbers the 8 pin fet is the one i was referring to.....are you willing to repair the board? otherwise just replace it.... did you test the power cord to verify its putting out correct voltage?

[CR Designs]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Yes want to repair board. power cord is good. does power have to be on to check 8 pin mosfet. you want to check 8 pin fet behind DC jack?Thanks for your help.

[CR Designs]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Tested 8 pin mosfet results

1 1
1 1608
1 1608
1 1609

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Yes want to repair board. power cord is good. does power have to be on to check 8 pin mosfet. you want to check 8 pin fet behind DC jack?Thanks for your help.

no power is needed you can do live test but to be safe no power at all for now.. set your dmm to continuity and on that 8 pin fet right by the dc jack you will see a indented dot by pin #1 which is source pin 1 put one probe there and on the opposite side of ic is drain and put the other probe one pin at a time on all four pins if you see open or dead short , you will need to desodier it and retest... still read short or open then its bad most likely although on some fets the 4th pin is sometimes not used but since i cannot find data sheet on it i cannot verify the 4th pin however 3 pins are certainly drain...if you need an illustration i will put something together.... but it a simple test... the hard part will be that voltage regulator....

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Tested 8 pin mosfet results

1 1
1 1608
1 1608
1 1609

ummm here let me help ya out a bit read above post.... and you would want to lay it out like this

pin 1 & 8= 0.0
pin 1& 6 = 1650 etc etc....

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

here is a data sheet for a 8 pin fet it is NOT!!!!!!! the exact one you have just for illustration purpose only.....on page 5 has the pin layout.... so you know what pin is what....

[CR Designs]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Did test mosfet

1 & 8=1
1 & 7 =1
1 & 6 =1
1 & 5 = 1

Did test they all tested 1, looked at diagram the pins were opposite from the one on my board. But I did find the indent you mentioned for pin 1.

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

http://www.ebay.com/itm/5PCs-B20PO3-...-/321003867753

take a look at this does yours have same symbol and the very bottom number is date code the number we want is b20p03 still looking for actual data sheet and cheaper source for this ic..... the readings your getting does not look right so i need to verify exactly what this ic is .....may need you to take it off and retest but hold on before you do so.....let me hunt for more info...

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Did test mosfet

1 & 8=1
1 & 7 =1
1 & 6 =1
1 & 5 = 1

Did test they all tested 1, looked at diagram the pins were opposite from the one on my board. But I did find the indent you mentioned for pin 1.

on continuity when you touch your probes together what does it read?

[CR Designs]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

It reads 00.3

[CR Designs]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

the mosfet number is B20P03 same as one on e-bay

[CR Designs]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

Also the mosfet symbol is the same as the one on E-Bay

[heavymachines]

Re: ASUS u31sd LAPTOP WILL NOT TURN ON

gonna assume you have very little solder experience you may want to practice on a junk motherboard or anything that has smd and sot chips on it... that way your ready to do it on the one you want to fix....



okay this is good however your readings aren't so good ...we will need to take this ic off and retest could be another component in circuit giving you false reading..... do you have a good quality solder iron? this is important cheap irons will overheat the component and still won't get the ic off without damaging something.... there is tons of soldering videos on youtube you can watch and train yourself how to deal with smd and sot packaged ic's... you can never use to much flux so don't be shy with it and you will need rubbing alcohol to clean the mess afterwards....q tips and paper towel i use this wonderfull stuff called chipquick to remove ic's however you can do without just flux and solider braid is a must.....



how i do it is flux both sides of ic then solder a solid bead on each side and go back and forth quickly to keep it liquid and use a dentist pick or tweezers to move the ic off the pads never force it....and be careful not to overheat the ic..chipquick makes it much much easier to do this because it keeps the solder liquid for long time...
now to clean the excess solder i use the braid and put it on pins then iron on top of braid this will wick the pins clean.....


when you put it back on with old or new ic you flux the pads on board set ic and align it and remember where number 1 pin is and always points towards white line on board or arrow and you have two ways to do this bead solder on both sides again and wick excess up or do each pin individually and solder each corner to hold the ic in place for you.... there are tons of youtube vids that will give you a good idea how to handle this...