EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: unturned3 on September 30, 2022, 08:03:48 am
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I recently purchased a Wifi module and I noticed a cracked SMD inductor on the back. The seller assured me that this is a common surface crack, and it would be fine since the inductor's ferromagnetic core is not damaged. However, that sounds somewhat dodgy to me... not sure what do you all think?
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It IS a ferrite core that is cracked. It's parameters should have changed a bit but inductor should still be functional.
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It is not just cracks but some small parts missing. This would reduce the inductance somewhat, but not very much (e.g. < 10% range). So Chances are very high it is still functional with no real negative effect.
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It is not just cracks but some small parts missing. This would reduce the inductance somewhat, but not very much (e.g. < 10% range). So Chances are very high it is still functional with no real negative effect.
Unless of course the stem of the core is also cracked, but that's not visible from up top. You could try wiggling the inductor, see if it budges.
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if the top is just chipped off in the corner it should be OK unless the circuit was way too optimized or barely functioning. The inductor tollerance is wide usually, so you have a few % change.. but chances are its in spec, since it might be +-30% part.
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It is not just cracks but some small parts missing. This would reduce the inductance somewhat, but not very much (e.g. < 10% range). So Chances are very high it is still functional with no real negative effect.
Tried this out to verify, measurements taken in circuit, cracked off the top:
- Original: 4.46uH Rs 89mR
- 25% crack: 3.85uH
- 60% crack: 3.15uH
OPs looks something like 20% of the top has been cracked off, so probably around the 10-15% reduction in inductance range.
if the top is just chipped off in the corner it should be OK unless the circuit was way too optimized or barely functioning. The inductor tollerance is wide usually, so you have a few % change.. but chances are its in spec, since it might be +-30% part.
-15 to -20% is the most common tolerance option. -30% does exist though.
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i stand corrected, its dodgy. Some how I missed that its WiFi. You don't want messed up inductors near a radio.
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i stand corrected, its dodgy. Some how I missed that its WiFi. You don't want messed up inductors near a radio.
At its frequency of operation it's pretty much irrelevant to WIFI, so only concern is about buck converter working properly.
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i stand corrected, its dodgy. Some how I missed that its WiFi. You don't want messed up inductors near a radio.
At its frequency of operation it's pretty much irrelevant to WIFI, so only concern is about buck converter working properly.
If it even is part of buck regulator. There is suspiciously nothing nearby that would scream "voltage regulator". Could be on the bottom PCB side, of course, but the whole group could as well be part of a filter for a voltage rail.
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Thanks for the replies everyone! I'll test this module once I get access to a Linux machine (sadly the drivers aren't available on MacOS 12.4) and will report back if I notice any oddities.
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Once I took apart my old Kingston SSD, and found that one of inductors is missing piece of it's core. Missing piece was nowhere to be found inside case. Disk works just fine.
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well when this happened on a pickit3 for me it would act up, but that was on a regulator
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L1 seems to form LC filter together with C8, GND referenced. As C8 seems to have quite a capacitance, I would not bother about chipped -off inductor. Most likely it is power input or output and loss of inductance here does not matter much.
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Just verified the WiFi board on a Linux machine; it does indeed work. Thanks again everyone!