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

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

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 !

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Lemmy

@DanR:

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

@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.

_________________
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@DanR:

Thanks for the reply.

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


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!

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

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

_________________
Lemmy

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.

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?

_________________
A backup a day keeps DR away.