HP NC2400 - need to identify burnt component

[scokljat]

Hi!

There is visibly burnt component on HP NC2400 laptop mainboard. Laptop powers up for a second, fan spins, nothing on display, no backlite, shuts down after few seconds.

Component location on the mainboard is PL17. Component itself looks like small smd capacitor but it's probably a filter, coil or something else.

What is this component? What to use in it's place? See pics...

How to check these four FET-s? (two from each side of board) They all measure 10-12ohm source-to-drain in circuit.

Any help is more than welcome!


Thanks!!!

Cheers,

S

[selldoor]

Re: HP NC2400 - need to identify burnt component

L is usually an inductor - can you tell what L17 is on the other side.

Having said that PL18 does not look like an inductor BUT it does look burnt.
Check what it is from part number.

Think you would have to take them off the board to test

PM the poster here and ask him in case he doesnt see the post
https://www.badcaps.net/forum/showth...ight=hp+nc2400

[scokljat]

Re: HP NC2400 - need to identify burnt component

L is usually an inductor - can you tell what L17 is on the other side.

Having said that PL18 does not look like an inductor BUT it does look burnt.
Check what it is from part number.

Think you would have to take them off the board to test

Thank you for quick reply :-)

Well, PL18 has some glue residue on it so maybe it just does look burnt on picture, but actually it's not...

How do I measure inductors? I have ESR micro 4.0s. It shows 0.05ohm for PL18 and 0.48ohm for L17.

Thanks!

S

[scokljat]

Re: HP NC2400 - need to identify burnt component

Here is better picture of PL18

[selldoor]

Re: HP NC2400 - need to identify burnt component

Yes - PL18 is a 0.47UH inductor and looks ok in that last pic. So I would say PL17 is an inductor as well.

[scokljat]

Re: HP NC2400 - need to identify burnt component

Here is picture of PL7 from another part of the board. It's probably the same component as burnt PL17. It reads 0.02ohm measured with ESR meter.

What if I just short this place for PL17?

[selldoor]

Re: HP NC2400 - need to identify burnt component

The inductor allows dc to pass through but impedes ac if there is anything downside of the inductor that will be damaged by ac then I would say No but I dont know enough about circuits to advise you. Hopefully someone else who does know will join us.

[scokljat]

Re: HP NC2400 - need to identify burnt component

The inductor allows dc to pass through but impedes ac if there is anything downside of the inductor that will be damaged by ac then I would say No but I dont know enough about circuits to advise you. Hopefully someone else who does know will join us.

So, PL17 died for a reason to protect other components from further damage? That means there might be a bigger initial problem that was the reason for PL17 burnout...

[rievax_60]

Re: HP NC2400 - need to identify burnt component

I have seen chip inductors burn out for their own reasons.
But if there are other problems, then bridging it out might cause even more damage.
Looks like it feeds battery or adapter DC to a low voltage buck regulator, Vcore supply I think.
Its best to check for shorted MOSFETs for now.

[scokljat]

Re: HP NC2400 - need to identify burnt component

I have seen chip inductors burn out for their own reasons.
But if there are other problems, then bridging it out might cause even more damage.
Looks like it feeds battery or adapter DC to a low voltage buck regulator, Vcore supply I think.
Its best to check for shorted MOSFETs for now.

You are right. I found the problem! There was a short at Vcore to ground. I started to remove SMD components at Vcore supply one by one to find which one is shorted. First I removed all four FET-s, than I removed large SMD caps, large diodes, small caps, coils and finally just when I was about to quit I removed few more small SMD caps, one of them was shorted!! Visually it looks 100% OK but it's shorted.

Well, I found the cause for short and inductor burnout, but now I have to clean the board and solder back 20 fragile SMD components... and than install new capacitor and coil.

Stay tuned...

Suad

[scokljat]

Re: HP NC2400 - need to identify burnt component

SUCCESS!!!!

I soldered all SMD's back (not an easy task). Everything went smooth, only thing I screwed is I damaged casing of PL18, but no damage. For now I've put a jumper short on place of burnt PL17. I left empty place where I found shorted capacitor. It is 10uF small non-polar ceramic SMD. I don't have anything similar that high capacitance. There is no enough place for standard 10uF cap...

Laptop powers up, everything looks normal.

Need to find solution for PL18 coil and small 10uF SMD cap. Any suggestion??

Thanks for your help!

Cheers!

S

[selldoor]

Re: HP NC2400 - need to identify burnt component

Well done - I must have put a curse on it - said it looked burnt and now it is

I couldnt read the part number have you worked out what it is ?

[rievax_60]

Re: HP NC2400 - need to identify burnt component

Wow, I didn't expect you to go so deep. I am curious how you removed the parts so neatly, quickchip desolder?
Although it seems that PC73 is across Vin and ground. You might have been tricked by the normally low resistance between the Vcore rail and ground caused by the CPU being in circuit.
The finding of replacements for the capacitor and PL17 is where I would have trouble also. Are you planning to look for them on old mainboards?

[scokljat]

Re: HP NC2400 - need to identify burnt component

Wow, I didn't expect you to go so deep. I am curious how you removed the parts so neatly, quickchip desolder?
Although it seems that PC73 is across Vin and ground. You might have been tricked by the normally low resistance between the Vcore rail and ground caused by the CPU being in circuit.
The finding of replacements for the capacitor and PL17 is where I would have trouble also. Are you planning to look for them on old mainboards?

I removed all parts with standard soldering iron. Well, it's a quality Weller 24V with temperature regulation and decent top. Sometimes I use BGA rework station, but this time Weller did the job.

I didn't find direct replacement for burnt 10uF capacitor. Actually I never saw 10uF cap so small. The best I have in this small package is 200nF, so I put a standard 10uF aluminum cap. As for the PL17 coil I didn't find any replacement so I installed a jumper ;-) Big coil PL18 suffered only superficial damage a I damaged the casing pressing it to hard when installing back to motherboard. Works ok.

So, Laptop is functional again, works great :-)

Thanks and cheers!

S