Asus K55VD - No Power -

[ShadowKarma]

Hi,


I have an Asus K55VD Mobo Rev 3.1. As the title says it has no power. Does not boot up, no lights turn on, nothing.

I have learnt quite a lot so far but still not got it working.

- I have 19V coming into the board from the charger.
- There is nothing I can find on the board that is getting hot. (Doesn't mean I haven't missed something though.)

Following another thread on here I thought I had found the problem, and not being to handy in following the schematics and so yet I went ahead and ordered a ITE IT8517E, when it came I replaced it and ethusaticly connected it up..... nope nothing, still as dead a dodo.

So back to learning how to follow what where. I had since learnt that i should have a 3V and 5V always on power line. So I kicked up PCBrepairTool and found if you search for VAO it will show you the +3VAO and +5VAO and can click on these and thus find the power line. Both seem to begin at PU8100 a PWM controller RT8239BZQW//RICHTEK WQFN-20 (If I am reading the "flow" of the power rail correctly) Well I followed all of the points and didnt measure any 3V or 5V anywhere. Went searhing for the datasheet...

http://www.datasheets360.com/pdf/914546746684425002

From what i gather I should at the least have some input voltage between 5.5V and 25V at pin 11 (also 8,9,10,12,16,17,18?? all seem connected) im guessing 19V as this is what comes it at the charger. Though what I measure there is 0.87V

Back to PCMRepair Tool then, I found a "Show the same net" and this then showed 2 extra points what looks like a resistor and a cap, RefDes PC8101 and PC8102, also on these points I see 0,87V.

So from what I gather the IC that is meant to create the 3V and 5V always on is not getting the correct input voltage it needs to do this, though I am a little stuck where and how to go from here.


Looking forward to your responces.
Thanks in advanced.

[ShadowKarma]

Re: Asus K55VD - No Power -

After some searching, the N-Mosfets, PQ8801 and PQ8802 are also showing this 0.87V...

The one connected to the positive side of the charger jack J6001, shows the same 19V on all 4 pins (which I believe is actually just one pin according to PCBRepair Tool_ pin 5, A/D_DOCK_IN, which I assume would be correct. Though on the other side 0,87V and the mosfet connected to it PQ8802 also has this voltage.

Testing the mosfet PQ8801 using the diode testing mode, it does not beep between any of the pins, would this mean it is suspect? Damaged?

Testing PQ8802 Pin 5 beeps to Pin 1,2,3 and shows a value of around 50

Hope I'm onto something here, my lack of knowledge is stopping me in my tracks. A schematic of the K55VD wouldn't hurt either.

[highpulse]

Re: Asus K55VD - No Power -

shadow karma , just add this one on the bench in the moment and its fixed , similar issue ,

client upgraded bios , and pc died , once it arrive here , no 3.3 and 5 volts and i had a stupid consume of 0.03 , reflashed bios , but same thing . then noticed that main reg for 3.3 and 5 volts , was getting a bit hot , everytime i cheked coils to gnd they seem ok , like no short at all , more than 10kohm each coil , cheked all LDO and EN pins , all good , hi drrive low drive gate no problem , , so inject 3 volts on both coils to see wich one line was having issues and , and the (5 volts coil, i only found out after cheking a similar schematic , was having a consume of 0.09 amp consume , and RT was getting hot . so once i figure wich was the 5 volts coil ,injected 5 volts on that rail , once i done this , RT started to act normally, working and turning on (attention you wil have only 5 volts on s5 , 3.3 volts will start once the machine is turned on .

somehow , injecting the 5 volts on the 5 volts line , errradicated some kind of energetic residue , or anything else .
hope it help you in case you're having same symptoms

[ShadowKarma]

Re: Asus K55VD - No Power -

A little bit above my head at the moment, how are you flashing the BIOS if laptop has no power? External flasher?

Are you saying i should just inject 5V on to the 5V rail? Does it matter where? Is that a good idea?

Also does my description of the mosfet sound ok? If that is damaged I don't want to go cosmetically injecting power :P

[highpulse]

Re: Asus K55VD - No Power -

about mosfet how to test
outside board , if NPN (red probe on source , and black probe on drain , must give you a value (if it beep or give 1 , then its damaged. in any case if it give you a value , then reverse the probes , and it might give you value 1 (infinite) now turn back again to previous probe position and keep black probe on drain and with red probe click onde on pin 4 (gate) then touch with red probe on source side (it will make continuity and beep in diode mode and if you switch probes it must make continuity as well , to deactivate gate again , reb probe on drain black probe on gate , and its back to normal state

for PNP its the reverse of the above explanation

[ShadowKarma]

Re: Asus K55VD - No Power -

Ok, I think Im following...

This is mosfet in question.


it is a N-MOSFET making it a NPN right?

Red on source, black on drain value of 507
reversed - open - value 1

then:
Red on source, black on drain, 507
Red on gate, black on drain, 538
Red on source, black on drain 1000, and drops down to 507 again, no continuity.

Did I do it right? Was a little bit confusing at first but I think I understand it now.

[ShadowKarma]

Re: Asus K55VD - No Power -

Well i think i have found my problem,

I found another MOSFET, PQ8806 this one does act as you decribe.

PQ8801 acts as above
PQ8802 is constant beep between drain and source no matter what.

Thanks for the lesson!

Now time to find some parts.

[ShadowKarma]

Re: Asus K55VD - No Power -

Well i replaced the PQ8801 mosfet first, went to measure it as above, it also gave "bad" readings.

What worth noting is, is when the mosfet is out of circuit it does measure "good".

So I do not suspect the mosfet I think anymore.

Does anyone else have any ideas of what I can measure/check?

[Mario]

Re: Asus K55VD - No Power -

Does the laptop power up with charged battery? I have laptop with same issue. No 5v rail. 3v3 rail is 1.2 volts. Got a charged battery would power up from that but not detect ac.

[ShadowKarma]

Re: Asus K55VD - No Power -

I have no way to charge the battery externally as of yet.... So I can't test this at the moment.

Thanks for your input. Is there anything else I can measure of test?

[ShadowKarma]

Re: Asus K55VD - No Power -

No one else with any smart ideas they would care to share? please

[dmartins]

Re: Asus K55VD - No Power -

I have the same problem ,

did you fix the laptop ?

With a fully battery my laptop works

[ShadowKarma]

Re: Asus K55VD - No Power -

Unfortunately I still need a solution.

[dmartins]

Re: Asus K55VD - No Power -

i'll check , if i get something new i tell you

When i plug in the charged battery the computer works and charge , but when i unplug the battery the computer shutdown

[dmartins]

Re: Asus K55VD - No Power -

Sorry the computer is not charging

[dmartins]

Re: Asus K55VD - No Power -

I changed PQ8801 and PQ8802 , and my computer works again..

[angel-boy]

Re: Asus K55VD - No Power -

I have a problem with K55VD rev2.1 , after power up , the memory on board is very hot hot, and numpad led is on. where to look ?

[angel-boy]

Re: Asus K55VD - No Power -

i remove all memory , is no short now , but still no image and numpad led is on

[Pragmatiko]

Re: Asus K55VD - No Power -

Hi,


I have an Asus K55VD Mobo Rev 3.1. As the title says it has no power. Does not boot up, no lights turn on, nothing.

I have learnt quite a lot so far but still not got it working.

- I have 19V coming into the board from the charger.
- There is nothing I can find on the board that is getting hot. (Doesn't mean I haven't missed something though.)

Following another thread on here I thought I had found the problem, and not being to handy in following the schematics and so yet I went ahead and ordered a ITE IT8517E, when it came I replaced it and ethusaticly connected it up..... nope nothing, still as dead a dodo.

So back to learning how to follow what where. I had since learnt that i should have a 3V and 5V always on power line. So I kicked up PCBrepairTool and found if you search for VAO it will show you the +3VAO and +5VAO and can click on these and thus find the power line. Both seem to begin at PU8100 a PWM controller RT8239BZQW//RICHTEK WQFN-20 (If I am reading the "flow" of the power rail correctly) Well I followed all of the points and didnt measure any 3V or 5V anywhere. Went searhing for the datasheet...

http://www.datasheets360.com/pdf/914546746684425002

From what i gather I should at the least have some input voltage between 5.5V and 25V at pin 11 (also 8,9,10,12,16,17,18?? all seem connected) im guessing 19V as this is what comes it at the charger. Though what I measure there is 0.87V

Back to PCMRepair Tool then, I found a "Show the same net" and this then showed 2 extra points what looks like a resistor and a cap, RefDes PC8101 and PC8102, also on these points I see 0,87V.

So from what I gather the IC that is meant to create the 3V and 5V always on is not getting the correct input voltage it needs to do this, though I am a little stuck where and how to go from here.


Looking forward to your responces.
Thanks in advanced.

i got your same problem and solved replaced n-Mosfer PJ8803 and PJP6001

[digitalPimple]

Re: Asus K55VD - No Power -

Do you have the mosfets specs you used?

Any 20v? dealing with the exact same here.. thanks.