On Jun 19, 2013, at 9:23 PM, allison <ajp166 at verizon.net> wrote:
I wonder what
else our lab staff was doing that kept blowing 1488/1489
chips?
The most common is really bad static. I've also seen people pulling RS232 plugs
with either piece live, if ground is the pin that breaks first then you may 24V at
the wrong place.
The other is safety ground that has potentials from one outlet to another.
Most common reason for that is neutral and ground swapped or a peice of
gear using ground instead of neutral for the return.
I've seen more than a few outlets in NYC and other places where from the ground pin
on one outlet to an outlet ground pin on a different breaker had 25V AC! I even
had one that had 119Vac (ground and line swapped!).
Be very careful what you call ground.
I'll echo this. We had a problem with a board we built where we amplified
our ~45 MHz IF with some really fancy, expensive 2 GHz buffer amps (our
customer had some really outlandish skew requirements for I and Q). We ran
into a problem where, after some indeterminate period of time, the buffer
amps would end up distorting like crazy and have to be replaced (made all
the worse because they were QFN parts with a heat slug on the bottom).
It turned out that the problem was a ~60V potential difference between the
grounds on the outlets we had the two soldering irons plugged into in two
spots on the bench. As soon as someone tried to pick up something with
both irons (e.g., an SMD resistor), you put a 60V potential across whatever
part of the board you were working on. The buffer amps did NOT like that.
We figured out the problem when we noticed that LEDs were lighting up when
we picked them up with two irons.
- Dave