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 Post subject: Which resistor at R25 on C20V-2.0-SM3257EN USB flash drive?
PostPosted: April 7th, 2021, 11:54 
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Joined: July 7th, 2014, 6:44
Posts: 167
Location: Switzerland
Hi there,

We received this not detected USB 2.0 flash drive for data recovery and have serious reasons to think that the resistor at location R25 could be missing.
Does anyone have this board model and could take a good quality picture of the resistor, or tell us the resistance value?

Attachment:
File comment: C20V-2.0-SM3257EN-L48-2L
-1F (LGA TSOP)-1.0

flash_drive_SM3257EN.jpg
flash_drive_SM3257EN.jpg [ 142.9 KiB | Viewed 355 times ]

Circuit board:
Code:
C20V-2.0-SM3257EN-L48-2L
-1F (LGA TSOP)-1.0 2011-02-25

Controller: Silicon Motion SM3257EN

Attachment:
File comment: R25 location on C20V-2.0-SM3257EN-L48-2L
-1F (LGA TSOP)-1.0 board

flash_drive_with_resitor_torn_off.jpg
flash_drive_with_resitor_torn_off.jpg [ 133.97 KiB | Viewed 355 times ]

Reasons for us to think that a resistor at R25 is missing:
  • Under the microscope, the resistor at R25 appears having been torn off: the weld is not smooth but abrupt shaped.
  • The customer told us the flash drive was intermittently working during some time when he pressed on it.
  • Another picture of the same circuit shows the presence of a resistor at R25: http://www.datasheetcafe.com/wp-content ... EN-DI1.gif
    Unfortunately it is too blurry to allow reading the resistor value (if printed on it).
  • There are no other apparent damage and replacing the USB connector does not bring anything.

On the shell, one cannot read the brand name anymore and the customer cannot remember it, but likely a popular model from Emtec or so.
Attachment:
File comment: Plastic shell from C20V-2.0-SM3257EN-L48-2L
-1F (LGA TSOP)-1.0

shell-from-flash-drive.jpg
shell-from-flash-drive.jpg [ 15.74 KiB | Viewed 355 times ]

Thank you for your kind help.


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 Post subject: Re: Which resistor at R25 on C20V-2.0-SM3257EN USB flash dri
PostPosted: April 7th, 2021, 15:49 
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Joined: September 8th, 2009, 18:21
Posts: 13117
Location: Australia
The resistor appears to be in series with the +5V supply. Typically it would be 2R2 (2.2 ohm) or 1 ohm. You could use a wire link or a fuse, but first verify that there is no short between ground and the load side of the resistor.

See pin #37.

http://www.datasheetcafe.com/sm3257-datasheet-pdf/

http://j5d2v7d7.stackpathcdn.com/wp-content/uploads/2015/10/SM3257-datasheet.gif

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