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 Post subject: USB Memory Stick not detected
PostPosted: December 5th, 2011, 10:39 
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Joined: November 21st, 2011, 10:05
Posts: 57
Location: England
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


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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 5th, 2011, 10:56 
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Joined: November 9th, 2006, 15:15
Posts: 2991
DanR wrote:
- Possible crystal oscillator?



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


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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 5th, 2011, 11:54 
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Joined: May 3rd, 2011, 9:52
Posts: 178
Location: France
DanR wrote:
- 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 !

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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 5th, 2011, 14:55 
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Joined: May 6th, 2008, 22:53
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Location: England
@DanR:

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


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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 5th, 2011, 16:48 
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Joined: November 21st, 2011, 10:05
Posts: 57
Location: England
@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.


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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 5th, 2011, 16:53 
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Joined: November 29th, 2006, 10:08
Posts: 7855
Location: UK
DanR wrote:
@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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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 5th, 2011, 17:20 
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Joined: May 6th, 2008, 22:53
Posts: 2138
Location: England
@DanR:

Thanks for the reply.
DanR wrote:
Unsure of history

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

DanR wrote:
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!


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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 6th, 2011, 7:14 
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Joined: November 21st, 2011, 10:05
Posts: 57
Location: England
Taking the chips down to the lab tomorrow. Will post results (if any)


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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 6th, 2011, 11:27 
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Joined: May 3rd, 2011, 9:52
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Location: France
There is no reason that the memory chip is dead. So you will have result but the difficult part is to reconstruct the data...

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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 6th, 2011, 13:35 
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Joined: January 8th, 2008, 5:21
Posts: 937
Location: uk
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.


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 Post subject: Re: USB Memory Stick not detected
PostPosted: December 7th, 2011, 21:43 
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Joined: September 8th, 2009, 18:21
Posts: 14945
Location: Australia
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?

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