[SI-LIST] Re: A short story
- From: "Matthias Mansfeld" <m.mansfeld@xxxxxxxxxxxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Sat, 09 Apr 2005 10:15:00 +0200
On 9 Apr 2005 at 0:05, Suresh Subramaniam 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!
On a populated board you measure not short or opens between traces,
you measure the resistance of _all_ components/networks on these
individual voltages (ICs, their blocking caps, regulators, some diode-
like stuff, pull-up-resistors to any logic outputs.....).
The remeasurement after power off may be wrong because of voltages in
capacitors (just wait a while and measure again) or because you
changed the measurement polarity on 2.5V rail.
Regards
Matthias Mansfeld
--
Matthias Mansfeld Elektronik * Leiterplattenlayout
Neithardtstr. 3, 85540 Haar; Tel.: 089/4620 093-7, Fax: -8
Internet: http://www.mansfeld-elektronik.de
GPG http://www.mansfeld-elektronik.de/gnupgkey/mansfeld.asc
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