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Re: gEDA-user: How to find which specific part of a PCB is shorted?



On 08/31/2011 07:09 PM, Kai-Martin Knaak wrote:
Thomas Oldbury wrote:

I am getting these messages:

Warning! Net "3V3plus" is shorted to net "GND"
Warning! Net "GND" is shorted to net "3V3plus"

The 3.3V bus is used all over the board. How can I locate
specifically which part is shorted?
This is what I do:

1) open the net list window

2) click on one of the offending nets. The right side of the netlist
window will show all the pads and pins that are connected to this net.

3) double click a pin or pad. On the canvas, the cursor warps to the
pin.

4) move the mouse slightly

5) zoom in

6) type [f] while te mouse hovers over the pin or pad

7) follow the highlighted path to see, where it goes off-road.

Step 4 and 5 are really only necessary, if the pin count is fairly
large.

If the offending connection is to ground, like in your case, and there
is a ground plane, then there may be find color all over the place. So,
there is no visible path to follow. In that case, I put the polygons
into their own layers with their own, private layer group. They are not
considered connected anymore

If everything else fails, I resort to plain old bisection: Remove the
right half of the layout and check, whether the short goes away. Repeat,
until you spot the problem. Then revert to the complete layout.

---<)kaimartin(>---
Since we have such a good, algorithmic method for finding these shorts, perhaps we can write some code to do it for our puny human minds? ;)

Usually, when I have power and ground shorted, it's because of a via placed some where that was accidentally assigned thermals to the wrong layer.

-Ethan


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