A real head-scratcher

Jay Honeck wrote:
[JPI EDM-700 engine analyzer missing seven-segment display segments]

Now for the odd part: The missing segments of the LEDs are NOT
consistent. For example, the same section of LEDs might improperly
display an "8" with a couple of missing segments on the right side of
the 8 -- but the next second it will change to a "9" and those right-
side segments will appear normally!

Disclaimer: This is based on experience with ground vehicles and
equipment. I don't have an A&P; I don't even have a TG&Y. Your mileage
may vary.

I'm going to add my vote for a bad connection or cold solder joint
internal to the analyzer.

The time-honored diagnostic is to thwack it with your finger and see
if the display changes.

If you're feeling adventurous, temperature-cycle it to see if the
display changes. Like: go to the hangar at 6 AM after the plane has
been sitting all night, turn on the master, and check the display.
Then, put your calibrated fingertip next to the display, and very
carefully direct a hair dryer (on low) at the display to see if it
changes. If your finger gets too hot for comfort, shut off the hair
dryer.

It's not _impossible_ for the internal programming to change on its own,
but it's highly _improbable_.

Disclaimer: This is based on experience with ground vehicles and
equipment. I don't have an A&P; I don't even have a TG&Y. Your mileage
may vary.

Matt Roberds