Dessoldering large smd inductors

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Narciso Peleida

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Hi,
I am trying to repair an HP Pavillion dv5000 laptop which will not turn on. All front leds are off. The AC adapter is OK. I took it apart and checked the motherboard and found out 2 large SMD inductors near ther processor (L8 and L9) which are open circuit. As I have never dessoldered inductors like this, I would be grateful if anyone should help me with a hint on how to dessolder properly theses components for replacement. I was told that hot air gun is not recommended for this job.

Many thanks

Peleida
 

two soldering irons each on one side of the inductor, where the inductors are soldered to the PCB.

Heat the PCB and with a third hand lift the inductor.

Then place the new inductor on the existing pads and solder the terminals.

Best luck.

Mandi
 
As above - removing the solder with desoldering braid just makes it harder sometimes. Having a solder joint with plenty of solder allows you to melt the solder and the component float on it and be lifted off.

My question would be is that are you 100% sure that these are inductors and open circuit?
I'd say its very strange for 2 inductors to go open circuit "just like that". There must be a reason - possibly that more than the max current has been drawn through them - and even then its usually something else in the circuit that fails.
 

Or to consider a trivial explanation, incorrect measurement.
 

Hi,
If the solder inductor joints are dryied too much it might prevent current flow. Try resoldering with new solder and no-clean flux and see if it helps.

Sully Kubillas
 
I would like to add that these inductors are CPU_Core supply line filters connected to MAX1544RTL 27 and 34 pins and FDS6294 sources and 2xFDS6676AS drains conected in parallel or back-to-back. These two lines are connected together at the output to form VCore output. One of these coils has a smd power resistor (.001R) and it is OK. I thought these coils were damaged by permanent heating as they are near CPU. I woul appreciate very much your comments.

Narciso Peleida
 

Hi,

Following the tips given by some forum members I dessoldered the the two power inductors on my HP Pavillion dv5000 notebook and I tested them outside the machine. They were both OK. Inspecting the motherboard pads I could see some corrosion that (I think) prevented current flow to the processor as here the voltage is somehow 1,1V. Cleanig the pads and ressoldering the same inductors I have got continuity beeps from the multimeter on both inductors.
I mention this fact as it would be for help to anyone having the same problem.

Thank you very much for your help.

Narciso Peleida
 

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