RE: [SI-LIST] : Plane short

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From: Degerstrom, Michael J. (degerstrom.michael@mayo.edu)
Date: Mon Apr 30 2001 - 06:25:36 PDT


I've had good luck with Method One - to expand on this:

Dump in one or more amps of current between power and ground.
Take a high precision voltage meter and apply the "-" to the
area on the board where your power supply current is returned,
i.e., to your ground attach.

Now with the '+' terminal measure several ground vias while
searching for the highest potential. If the short is at
a via location then the highest potential is the location
of your short.

I've had the best luck if my top surface is ground so
that I simply use a sharp probe to pierce the soldermask
and then probe the ground plane instead of via locations.

Good luck,

Mike
_______________________________________________________________
Mike Degerstrom Email: degerstrom.michael@mayo.edu
Mayo Clinic; 200 1st Street SW ; Rochester, MN 55905
Phone: (507) 538-5462 FAX: (507) 284-9171
WWW: http://www.mayo.edu/sppdg/sppdg_home_page.html
_______________________________________________________________

> -----Original Message-----
> From: Michael Nudelman [mailto:mnudelman@tellium.com]
> Sent: Monday, April 30, 2001 8:00 AM
> To: 'Bastola, Subas'; si-list@silab.eng.sun.com
> Subject: RE: [SI-LIST] : Plane short
>
>
> 1. Method One. If your power supply is capable of providing
> undervoltage
> protection without pulsing (pumping more or less large
> constant current
> through the short) - measure the voltage drop gradient and
> find the short.
> Works for me.
>
> 2. Method Two. Using milliohmmeter and "Freeze" spray, find
> the place that
> reacts "violently" (rapidly changing resistance) while
> sprayed. This is
> likely (80-90%) to be the spot where short is. Also works for me.
>
> 3. There used to be a hand-held device on the market, size of
> a logic probe,
> that produced variable tone depending on the closeness to the
> shorted spot.
> Took me 2-3 minutes max to find the exact location (required
> good hearing -
> I have an absolute pitch).
> Problem - I've been trying to locate the device
> unsuccessfully for 4 years
> now. Seems like they either withdrew it due to the lack of
> demand or I do
> not know where to look.
>
> IF ANYONE KNOW ABOUT THIS ONE PSE LET ME KNOW - WILL BE
> FOREVER IN YOUR
> DEBT! :-))))
>
> Mike
>
> -----Original Message-----
> From: Bastola, Subas [mailto:subas.bastola@intel.com]
> Sent: Saturday, April 28, 2001 11:56 PM
> To: si-list@silab.eng.sun.com
> Subject: [SI-LIST] : Plane short
>
>
> What is the best method to find the location of a short
> between the power
> and gnd plane in a fully assembled board? Can TDR help?
>
> Subas Bastola
> Intel
>
>
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