I need help, please.
I was measuring the voltage of the USB pins on my ga-586tx3 and I've accidentally shorted an inductor known as L5 (please see attachments). I am wondering if anyone could tell me its purpose if know what its value is so I can replace it. Thank you in advance.
Good chance, that L5 has the same value as L6 (both are parts of the filters with C182 and C191). To be sure of the values, you'll need the board schematics. Inductor is a kind of hard to measure - needs to be taken out and measured with a LCR-meter.
Zerthimon wrote on 2023-05-29, 13:43:Good chance, that L5 has the same value as L6 (both are parts of the filters with C182 and C191). To be sure of the values, you'll need the board schematics. Inductor is a kind of hard to measure - needs to be taken out and measured with a LCR-meter.
Thanks for the information, I guess the next logical question is, are board schematics obtainable? I have asked a couple of vendors on e Bay if they are able to see any identifiable markings on the indicator on the product they're selling.
Are there any markings on L6 ?
These are for filtering the 5V USB supply voltage (EMV), they must stand the full current caused by the connected USB devices.
On early USB mainboards they used through hole "ferrite beads" with very low inductivity, very low DC-resistance (0.05 Ohm) and designed for currents of 1-2A.
There are also SMD ferrite beads for example the Murata "BLM21SP471SN1D" (form factor 805).
You can use anything like that, the impedance is not critical (about 500 ohm @ 100 MHz).
According to most application notes there was also a fuse in every supply line. This does not seem to be the case here. Maybe the original inductor is made of a thinner wire that melts in case of a short. Mainboard makers are very inventive when they can save a few cents.
If you choose a standard inductor instaed of a ferrite bead, just make sure the wire is thick enough to stand 1-2A.
Zerthimon wrote on 2023-05-29, 18:41:Are there any markings on L6 ?
Unfortunately not. I have another motherboard that's very similar, I'll have a look on there.
majestyk wrote on 2023-05-29, 19:30:These are for filtering the 5V USB supply voltage (EMV), they must stand the full current caused by the connected USB devices. […]
These are for filtering the 5V USB supply voltage (EMV), they must stand the full current caused by the connected USB devices.
On early USB mainboards they used through hole "ferrite beads" with very low inductivity, very low DC-resistance (0.05 Ohm) and designed for currents of 1-2A.
There are also SMD ferrite beads for example the Murata "BLM21SP471SN1D" (form factor 805).
You can use anything like that, the impedance is not critical (about 500 ohm @ 100 MHz).According to most application notes there was also a fuse in every supply line. This does not seem to be the case here. Maybe the original inductor is made of a thinner wire that melts in case of a short. Mainboard makers are very inventive when they can save a few cents.
If you choose a standard inductor instaed of a ferrite bead, just make sure the wire is thick enough to stand 1-2A.
Thank you so much for your reply. I have learnt a lot. That explains why the indicator blew due to the short and why the motherboard still appeared to function correctly.
