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Electronics => Beginners => Topic started by: Giorg on January 31, 2011, 12:31:48 am

Title: need help identifying smd component!
Post by: Giorg on January 31, 2011, 12:31:48 am
Hi everyone .. i'm new on the forum and i'm full of questions :D

(http://element2048.files.wordpress.com/2007/07/dscf0316.jpg)

I need your help to identify this little white smd component. It's directly connected to the usb data + and - line. The circuit is a usb wireless adaptor.

The component has been damaged and the usb connector was brutally bended.

I tought about an optocoupler but I can't find anything really similar.
Is there a "quick and dirty"  way to replace the component with something else?
I know that it's easier to buy a new one but i'm doing it only for the pleasure of fixing stuff :D i hate to throw away.

Thanks to all of you!
Title: Re: need help identifying smd component!
Post by: joelby on January 31, 2011, 12:50:26 am
It might be a USB port terminator and/or EMI/RFI filter. ON Semi sell these (http://www.onsemi.com/PowerSolutions/parametrics.do?id=832&lctn=home (http://www.onsemi.com/PowerSolutions/parametrics.do?id=832&lctn=home)), though I couldn't see one that matched yours.

It's probably okay to bypass it completely for testing purposes.
Title: Re: need help identifying smd component!
Post by: Mechatrommer on January 31, 2011, 11:48:12 am
It's probably okay to bypass it completely for testing purposes.
agree, maybe 2 EMI beads/ferrite combined together. a working bead just a short at both end, so continuity testing among pins might give some clue.
Title: Re: need help identifying smd component!
Post by: Zad on January 31, 2011, 02:44:39 pm
It could be ferrites (and I'm pretty sure it is a common mode choke) but it could also be an ESD protection diode cluster. Something similar to this.

http://www.farnell.com/datasheets/48344.pdf (http://www.farnell.com/datasheets/48344.pdf)

This one has 6 pins, but some only needs 4+gnd.
Title: Re: need help identifying smd component!
Post by: Mechatrommer on January 31, 2011, 03:18:02 pm
doing some digging treat on the rt2571wf chip. here's another picture from somewhere, it seems its just like two normal resistors, not sure the label, maybe 000. i bet thats the cheap replacement for the ferrites. or maybe its indeed 2 resistors joined together for smaller footprint i think, but if its 000's, then whats the point? ???
(http://yltan.com/blog/wp-content/uploads/2009/08/TP-LINK-TLWN321G-3-LARGE.jpg)
from a forum http://www.hak5.org/forums/index.php?showtopic=16971 (http://www.hak5.org/forums/index.php?showtopic=16971)

and here is the best i got for the datasheet/intro of the chip
http://www.datasheetarchive.com/rt2571*-datasheet.html (http://www.datasheetarchive.com/rt2571*-datasheet.html)
Title: Re: need help identifying smd component!
Post by: TheDirty on January 31, 2011, 03:40:25 pm
000 would just be 0 ohm jumpers.  It's basically been bypassed on that board.  It's possibly too expensive to add for the protection given.
Title: Re: need help identifying smd component!
Post by: Giorg on February 02, 2011, 10:41:28 pm
Thank you all for the suggestions!

I've done the bypass and the device it's back to life!

Now i'm just wondering if it safe to leave it without protection.. as the intention is to mod it with an external homemade antenna.

Title: Re: need help identifying smd component!
Post by: joelby on February 03, 2011, 12:32:57 am
It's probably fine, especially if you leave it connected to a computer all of the time, and considering that the other device pictured in this thread didn't bother to include ESD protection.

Title: Re: need help identifying smd component!
Post by: Mechatrommer on February 03, 2011, 03:05:50 am
afaik, ferrite is to prevent noise/spike from and to the usb data line and rt2571 from the look of the picture. you can probably damage the usb side (pc) if...
1) you make unnecessary hack/mod like adding voltage to it (wireless adapter) circuit.
2) there is super strong megatonne watt EMI going on around, which is very unlikely i think.
as the posibility damaging the wireless adaptor due to noise from pc, well, u just bring it back from death, then what are u worrying about? the second death may means RIP baby. and i believe if you motherboard is "no shit" brand, then it is well designed to prevent such event (noise). maybe you can still keep looking for the part, or leave it as is, the same to the linked picture by me above, in the mean time, enjoy the device! ;)

ps: be aware, ferrite or no ferrite, modding the device will render the warranty voided and possibly damaging your device (manufacturer advice) ;)
Title: Re: need help identifying smd component!
Post by: Giorg on February 08, 2011, 08:07:14 pm
Quote
2) there is super strong megatonne watt EMI going on around, which is very unlikely i think.

never say never :D

thanks again for all the precious information!

Now i must search for something that needs to be repaired and i'll come back with more questions  :P