USB Memory Stick not detected

[DanR]

Hi guys,

Haven't done much work on USBs so I'd thought i'd ask for your input.

- 4GB usb stick.
- PC does not detect any USB nor does the LED light up.
- No obvious burn marks.
- All fuses seem intact.
- Possible crystal oscillator?

Any suggestions?

Thanks in advance.

DR

[hddguy]

- Possible crystal oscillator?

This would by my guess, but accurate diagnosis is near impossible without seeing the media

[ici_lemmy]

- Possible crystal oscillator?

Would also be my first try. Easy to test with an osciloscope !
If the oscillator is working, then my guess would be the controler and you'll have to work on the memory chip !

[Vulcan]

@DanR:

It may be helpful to know the history of that USB drive, leading to the current situation.

[DanR]

@Vulcan

Unsure of history but there have been no previous DR attempts. Plug USB into computer and you get nothing.

@ici_lemmy

Tested using an oscilloscope. Was showing no 12MHz, so I presumed it dead. Replaced the crystal and still no 12MHz output. This leads me to think that the micro-controller is now dead.

[pcimage]

@Vulcan

Unsure of history but there have been no previous DR attempts. Plug USB into computer and you get nothing.

@ici_lemmy

Tested using an oscilloscope. Was showing no 12MHz, so I presumed it dead. Replaced the crystal and still no 12MHz output. This leads me to think that the micro-controller is now dead.

In which case you'll need to remove the flash chip, read it in and reconstruct the data.

[Vulcan]

@DanR:

Thanks for the reply.

Unsure of history

That's a shame for you, as having that info often helps troubleshooting, in my experience.

Tested using an oscilloscope. Was showing no 12MHz, so I presumed it dead. Replaced the crystal and still no 12MHz output. This leads me to think that the micro-controller is now dead.

There can be other reasons for your reported measurement, not only a dead controller.

As you've already seen, pcimage has explained a classic DR approach, if you are unable to repair the original USB drive.

Good luck!

[DanR]

Taking the chips down to the lab tomorrow. Will post results (if any)

[ici_lemmy]

There is no reason that the memory chip is dead. So you will have result but the difficult part is to reconstruct the data...

[dick]

Before doing anything drastic I would also always check the 4 contacts from the usb connector to the pcb for continuity. And it is a good idea to check for +5v and then check the +/- data lines to the controller.

[fzabkar]

Can you measure any voltage on the memory chip's Vcc pin(s)?

Is there a discrete 3.3V linear regulator IC on the PCB?