[SI-LIST] Re: A short story
- From: Martyn Gaudion <martyn.gaudion@xxxxxxxxxxxxxxxxxxxx>
- To: Suresh.Subramaniam@xxxxxxxxxx
- Date: Sat, 09 Apr 2005 16:59:11 +0100
Hello Suresh,
Apologies for the commercial response..
The exact tool you need is a Polar Toneohm 950
power - ground short circuit locator.
www.polarinstruments.com/products/toneohm/toneohm950.html
Heres an app note that explains more:
www.polarinstruments.com/support/pcb_troubleshooting/AP201.html
www.polarinstruments.com/support/pcb_troubleshooting/Toneohms%20find%20ground%20plane%20shorts.PPT
Kind regards
Martyn Gaudion
www.polarinstruments.com
At 08:05 09/04/2005, you wrote:
>Hello All,
>
>I am faced with the following situation: A fairly complex bare board
>shows no shorts between any of the power rails (1.2,2.5,3,3,5 and 12V)
>and GND. However, before power up, on a fully populated board, I am
>measuring about 10 Ohms on the 1.2V, 6 Ohms on 3.3V and 0.5 Ohms on 2.5V
>(measured with a standard Fluke multimeter) and the others are showing
>readings in the 1-2K Ohm range! Since we had several boards on hand, I
>decided to power up one of the boards anyway. There was no smoke or
>hotspots on the board (the 1.2V and 2.5V switching regulators are rated
>for 14A).. And more importantly, majority of the interfaces tested are
>operating as advertised. I remeasured the board after power off . Now
>the readings are ~100 Ohms on 2.5V and about the same as before on the
>other rails.
>
>(Note: The pattern is the same on all boards.)
>
>I have also checked to make sure there are no symbol/footprint errors.
>Before I start to depopulate individual ICs to trace this short on an
>unpowered board, I thought I would check in to find out if others have
>had this experience.
>
>Also, is there a better/correct method to measure pwr/gnd shorts ?
>
>Thanks
>Suresh
>
>--
>
>--
> / 7\'7 Suresh Subramaniam suresh.subramaniam@xxxxxxxxxx
> \ \ Xilinx Telephone: 408-559-7778
> / / 2100 Logic Drive Direct: 408-879-6172
> \_\/.\ San Jose, CA 95124 FAX: 408-377-9013
>
>
>
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