Electronics > Repair

Watchguard Firebox x750e Firewall - Help identifying an inductor?

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Hey all, I hope someone might be able to point me in the right direction. This picture is taken of what i suspect to be the faulty component.
I can tell that it is a 4.7uH inductor but having trouble identifying other specs like amp rating, tolerance percentage rating and what type. (SMD, High Frequency etc)
I have tried searching google and some other forums but no luck yet.

Is it important that it is replaced with the exact same specs or will a "close enough" 4.7uH inductor do the job?
If anyone has any ideas or suggestions I would be very grateful.

EDIT: Added some more photos

What makes you suspect it?

For a replacement, something the same size will generally do. Measure it and I'll point a few out.

Looks like Vishay IHLP series:


--- Quote from: evb149 on February 13, 2015, 06:05:23 am ---Well that inductor looks like it is part of a switching power supply.  Maybe the switching inductor in a buck converter or so.
Small inductors like that one are rarely the components that fail though the left side and the top (a bit) of the unit in your picture looks as if it has been a bit hot so maybe it did blow.  Unfortunately it would rarely be the inductor alone and itself that would fail in some kinds of converters, but rather they'd fail from overheating due to overcurrent which is persistent so there is the possibility that something else on the output side (?) of that inductor has failed and caused the inductor to draw too much current and overheat, but then usually there may also be problems with the transistors / diodes / capacitors in many cases when components in a SMPS fail.

The full story is that I attempted to install a new cpu into the motherboard. it was the correct socket and chipset but must have had compatibility issues elsewhere. as soon as i tried booting after the new cpu install, there was a large amount of smoke coming from that inductor. of course i switched it off but the damage had been done. I have also inspected the rest of the board and cannot identify any other damaged components. No discoloration or charring anywhere on the pcb or components.

Measure the size of the inductor square package, get a dimension of the square's diameter in millimeters.   There are families of surface mount inductors like that one that are sized to fit a particular footprint, so knowing the diameter of the square will help you narrow down the choices for a compatible replacement since others that are too large or too small would not be the same of course.

Cool. will do that when i get a chance.

The tolerance of inductors is usually loose, maybe +/- 20% is typical, so that's probably a fine tolerance to get as a replacement if it is a single coil inductor.   If it has only two electrically distinct leads it is a single inductor, otherwise if it has four it could be a coupled inductor but those are less common.

It looks like a single inductor, but i guess i will know more when i get it off the board.

The voltage rating isn't often an issue in low voltage DC side SMPS applications.

ok. good to know.

The RMS current rating, and saturation current ratings are big factors for compatibility, as is the related general value of the DC resistance though finding one with a similar RMS current / saturation current rating will generally mean that the DC resistance is similar also. 

If you can desolder the inductor and test its DC resistance to the nearest 10 milliohms and inspect it more closely you can learn if it is open circuit or has a reasonably large (compared to new units in the 4.7uH value and physical size) DC resistance that may indicate it is OK.  If the DC resistance is less than a few milliohms (say 4mOhm or less) it is likely shorted or something since usually they're a bit over that up to the couple dozen milliOhms range I'd guesstimate though lately I've use ones with a higher value so maybe the 4.7uH ones can get down to sub-10mOhm ranges in common practice and still be working.  Check DIGIKEY.

will do :)

Look for charring or leakage/bulging of capacitors, charring of resistors / transistors / diodes.

All other components have no physical signs of ware or leakage/bulging.

If it is a flyback or forward converter you'll have a harder time finding a functionally compatible inductor.  If it is a buck or boost converter it'll be a bit easier to replace it without likely throwing off the rest of the circuit.
I'll see if I see that 0543PH marking in some data sheet but you can also do it by downloading all the different 4.7uH surface mount inductor datasheets with that size package from DIGIKEY and maybe MOUSER and see if any look very similar and may have a "marking" convention that could result in it being labeled also 0543PH.

wow. ok thanks, i guess i have to wait till i measure it. But thank you for all your help. i may have some hope of fixing this thing yet.  ;D

--- End quote ---

added some more photos. thanks for the replies! i will measure it and get back to you all soon.
unless anyone else knows the model off hand?  ;)


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