Tracing Short Circuit to Repair Boards

<Sigh>

The informations you are needing usually comes about as the result of some type of formal education.

Or, if all else fails, read the instructions.

and the information about particular boards is almost always copyrighted and considered protected intellectual property

www.fluke.com/ohmmeter

One of the handy things that may be used is an octopus circuit like this:

http://octopus.freeyellow.com/octopus.html

or this:

http://www.tpub.com/content/neets/14191/css/14191_142.htm

The more refined version is the Huntron Tracker:

http://www.huntron.com/ad/fixboards.htm?gclid=COCE78K0lp8CFQghnAod_A2jJQ

These solutions may require that you have a good board to test against. If you do not have a good board then see below.

Another way to handle this is to apply a limited current to the board and see what part gets hot. It should go without saying that you Never exceed the rated VCC.

One thing I have done is to apply a limited current and measure voltage drops across circuit traces going to various components. If there is no voltage drop, there is no load on the circuit. The drop may only be a few micro volts.

When things get desperate, I have been known to cut circuit traces to isolate power to certain sections of the board. This is likely impossible with multilayer boards.

There is always the old blow and go method. You just supply sufficient current for the offending part to blow then you easily go to the chip or other component with the smoking hole/crack in it. This can be really messy and not a little dangerous with shorted or leaky electrolytic and tantalum caps blowing their stinking guts all over the work area. It can also destroy the circuit board if the component is capable of sinking more current than the circuit traces can pass without burning up.

About 25 years ago, I spent some time working on boards given up for dead at the end of a production line rework dept. I was trying to recover enough parts to finish the last contracted run of a now long obsolete product. I usually got them to work but some of them had actual PC board shorts due to poor etching, those were usually irreparable.

Have FUN!
TT3