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USB Stick/thumbdrive/flash drive plug broke... and now

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akshay

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The data+ and data- pads had come unglued from the PCB, so I soldered them back on. But the drive doesn't work. I've checked that all IC's get ground connection. The power is a little more complicated - it goes directly to a half k-Ohm resistor or such and then to the other chips. There's either a two-terminal regulator that I can't find because it looks like a SMD capacitor, or the USB controller has a built in down-converter. There's no three terminal series regulator that I can find.

The USB chip is PHISON PS2251-50. It's rated voltage is 2.6-3.7V, but when I plug in the USB drive now I get only 1.7V max at any of its pins. No datasheet available! I wonder if it's in a low power mode or if it's busted. I can't see why it's busted. The USB drive was plugged in when the plug broke, but can the data pins breaking destroy the controller chip? That seems odd.

Any recommendations on repair? The USB stick contains near-and-dear data of a friend.:-(
 

oyvdahl

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Does the drive show up at all when you plug it in? Or do you get any error messages? If so, then you should look at the resistors and make sure they are connected and working properly.
If nothing happens when you plug it in, you should look at the voltage at the D+ pin when plugged in. It needs to be pulled up by a resistor to indicate that there is something on the bus.
 
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    akshay

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KJ6EAD

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It sounds like one or more of the circuit paths has been cracked. Reflow all components near the connector and jumper in a new connector on a short cable to recover the data.
 
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    akshay

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akshay

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I only see 7ohm series resistors that go from the data wires to the PHISON USB controller. I'm assuming the pullups are internal? Also I've checked the components on the bottom... they seem to have connections! I agree that a track might be cracked on an internal layer, it's proven really hard to find though.

Also, I'm assuming that the memory chips get power from the USB controller which has a built in regulator? The confusing thing is that the PHISON chip, from what little data they have on their website,
PHISON Electronics Corp. Introduces the World's Best NAND Flash Solution
has an operating voltage of upto 3.6V, but USB is 5V! The supply to this chip seems to be going through 700ohm resistor! i.e. there's two 1.5k resistors between the 5V supply track and the phison chip. I don't know which is the VDD terminal on the chip, but I've checked that the highest voltage on any pin is 1.66V :eek:

The Data pins have 0V on them. :(
 
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