Fwd: Re: [Discuss-gnuradio] USRP1 USB I/F failure & repair

[Ryan Seal]

On Mon, 18 May 2009 19:26:58 -0400, Marcus D. Leech <address@hidden>
wrote:

> Matt Ettus wrote:
> > Paul Mathews wrote:
> >
> > Paul,
> >
> > Thanks for your analysis of the situation.  C73 and C74 are not
> > actually capacitors, they are, as you say, electrostatic discharge
> > protectors, part number PESD0402-060.  I have not seen any fail in the
> > manor you mention, but I suppose enough static could cause that.
> >
> > Has anyone else seen this failure mode?
> >
> > Matt
> Aren't ESD protectors usually MOVs, and don't MOVs usually fail by
> shorting?  They can absorb so many joules of ESD, and
>   after that they short out.
>
> In live electrical power lines,  this usually causes the breaker to trip.
>
> The other type are GDTs, which fail open.  But they don't fail very  
> often.

I used to work on power supplies some time ago. We had one particular
version with ESD protection on the output. They failed quite often, and
yes, they do short when they fail. I was never convinced that the devices
actually failed due to ESD, but more likely faulty manufacturing process.

Ryan