With regard to your question: "Also, is there a better/correct method to measure pwr/gnd shorts ?" One method is to use a thermal "sniffer" type probe. I don't recall the manufacturer or model since it has been years since I used this probe..but there are probes out there for this problem. I had a similar situation where we didn't have a short but a finite (low/unintentional impedance). We found the problem in a matter of minutes with this probe. The probe had a narrow light beam to show the area of the board being scanned...and I just moved the probe up and down the board until I found the hot spot. One issue is you could trigger the thermal sensor on a device that is supposed to be hot.. So it depends how much power this "unintentional short" is dissipating heat relative to other devices. With regard to the measured impedances...do you have a "good board" to compare? ..eg, Find out what the expected impedance to narrow down the problem (or pull out the schematics and start doing some calculations to see what the impedances should be ...) Good luck! Bob McCormick Hardware Engineer / SI Stratus Technnologies Maynard, MA -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Suresh Subramaniam Sent: Saturday, April 09, 2005 3:05 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] A short story 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 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu