I have a 64GB Lexar USB flash drive. When connected to the USB port, it is typically not recognized at all. If I insert it slowly (LOL, that sounds wrong), I can get a message from Windows saying a device connected to the USB port has malfunctioned. If I twist it around (why does this sound so dirty?) I can sometimes get the LED to flash about 3-4 times, then it shuts off and the unit still isn't recognized.

I don't have any 12 MHz crystal oscillators (four-pin) but in the past I've had some units with similar symptoms where replacing the crystal (two-pin) has revived them. Worth a shot in this case?

Any ideas?

Check also usb connections, that might be failing.

Yeah, thanks, it looks solid but I suppose I should touch them up, it sure can't hurt.

Yep, swap out the crystal. If there are no other physical signs of damage then there is a good chance the swap will fix it.

you can try:
- looking at the whole circuit under a magnifying glass for any damage/breaks to solder points.
- re-soldering carefully the usb connector
- as mentioned, replace the XTAL, maybe buy a couple of cheap drives, you may find one the same..
- send to a DR pace that does Flash
- you can try plugging it in, spraying with freeze spray. It shrinks the solder a bit and can sometimes show a different to no spray indicating there is a broken solder connection

I looked at some other flash drives, I found a 12 Mhz oscillator but it is physically too large. I could solder some leads between the oscillator and the board, but ug.

So I looked at Digikey. They have five types that are within the size range I need, but I'm not sure what type this would be.

The units at Digikey are: MEMS, SO, TCXO, VCTCXO, and XO (Standard). Do I need the XO (Standard)? It can't be that simple, can it?

The types of output are "CMOS," "HCMOS," and "HCMOS, TTL." Any idea?

TCXO and VCTCXO devices would be used in PLLs and applications where temperature stability is critical.

MEMS appears to be a replacement for XO with improved performance.

I would go with XO.

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A backup a day keeps DR away.

If you show me a photo of the board, I may have a matching one, or be able to tell you which USB Drive you can buy that might have a matching XTAL.

flash controller data sheets say to pay attention to how the circuit is laid out. They also mention which layer of the PCB some traces should be on, so for them to mention this, ISTM that it is not a good idea to wildly change the layou, such as using wire to join XTAL to board. It may or may not matter.

Also the capacitance of the XTAL might matter, for example some need a matching capacitor. You might be able to find the datasheet of your controller at places like flashboot.ru or usbdev.ru.

I am not convinced it is the XTAL..

Sounds great, I've included a pic.

That doesn't appear to be an oscillator. The existence of XC1, XC2, and R11 would suggest that the device is a quartz crystal. BTW crystals do come in 4-pin packages. Also, if the device were an oscillator, then it would have a power pin.

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A backup a day keeps DR away.

Okay thanks. So then we know (thanks 2 u) that it is a crystal, but has four pins that I can see. Any tips on finding a replacement that will be compatible?

Here are two datasheets:
http://www.vishay.com/docs/35064/xt35.pdf
http://www.adrirobot.it/datasheet/vari/ ... 2020pF.pdf

Obviously you would need to compare dimensions and pinout. I don't know about load capacitance, but I would expect that if you stick to a standard value, then you will probably be OK.

I would search Digikey, Mouser, Newark, Farnell, etc. Otherwise HaQue's suggestion re pilfering one from another flash drive might be the easiest solution.

That said, if the LED is flashing under control of the flash controller, then this would suggest that the crystal is oscillating. It could be operating at the wrong frequency, though. Like HaQue, I'm not convinced that the crystal is the problem.

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A backup a day keeps DR away.

I'm not certain it is the crystal, either. The way it behaves, though, is similar to other flash drives that I've revived by replacing the crystal.

I did crack-open a couple of other flash drives I have but I did not find any crystals that would fit.

Hmmm...

This appears to be the datasheet for your device:
http://www.candor-co.com/UpFiles/articl ... 96%B09.pdf (CSX-3225)

Other products:
http://www.candor-co.com/html/list_668.html

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A backup a day keeps DR away.

I cut the following diagram out of a USBest reference circuit and edited the circuit references to reflect the OP's PCB. It illustrates a typical crystal layout.

_________________
A backup a day keeps DR away.