Some quick, off hand comments imbedded below:

Steve N.

"Michael A. Terrell" wrote in message
...

Some questions. How are you going to position it against the trace
accurately?

First you do some controlled experiments where you put the test signal
through known runners to characterize the given pickup. How to orientate it
& where it picks up from.


What about double sided,

I don't see a problem. If you get it set up so it detects at sufficient
distance (.070 or so).

or multilayer boards?

Should still work, but you'll have to follow the target trace by "braile"
(sp) since you might not be able to see it.

The problems with using AC to find shorts is that you get false peaks
and dips from the inductance of the traces, and the characteristics of
the components.

At audio this can't be a problem. I'm convinced it will just be current
defined by the generator.

With a runner short you won't have much current in anything but the
runners anyway, no?

Another problem is that some parts self destruct with
only a small reverse voltage so you can damage a lot of parts while
troubleshooting the board.

Also, there won't be much voltage (remember the DC method?). If you do
have this, you're in risk of burning up runners. That's too much current.

I used the DC voltage drop & sensitive digital meter method on boards
that people couldn't fix with AC, then had to find the parts they
damaged. The whole idea is to find and fix a problem quickly, and
reliably.

Hard to believe a 600 ohm audio gen will blow up anything, but it certainly
is possible... of course you just don't go in there blazing away with
power..

I don't mean to say the DC method is bad, or that AC is better. AC is
just another option, especially if you don't have a good enough DVM. Seems
to me I saw a commercial system which did use AC.

My Fluke has problems under an ohm and at fractions of a volt even though it
is a 5 digit. Should be good down there. May try it to see how DC works
just for info.

73

--
Steve N, K,9;d, c. i My email has no u's.