A real head-scratcher

So we hop in the plane yesterday for the 50 minute flight to
Janesville, WI, and I notice that the display on our JPI EDM-700
engine analyzer looks funny.

Some of the LED numbers are missing pieces. Most are not. All the
vertical graph/bars appear to be fine.

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!

It's almost like the internal programming for the display of numerals
is screwed up, rather than the display itself?

Any theories here? I was hoping it would cure itself (ha!), but it
was the same on our flight today....
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

In article . com,
Jay Honeck wrote:

Any theories here? I was hoping it would cure itself (ha!), but it
was the same on our flight today....

loose internal connection?

--
Bob Noel
(goodness, please trim replies!!!)

Jay Honeck wrote:


Any theories here? I was hoping it would cure itself (ha!), but it
was the same on our flight today....
--

Could be moisture... it does interesting things to
little electronic circuits. The display on my Kx155
can do the same thuing for 30 seconds or so when
I first turn it on when in very humid weather.

Jay Honeck wrote:
So we hop in the plane yesterday for the 50 minute flight to
Janesville, WI, and I notice that the display on our JPI EDM-700
engine analyzer looks funny.

What's the bus voltage like? The first sign of a low voltage
situation on several planes I flew was that the KX155 displays
started losing segments.

Jay Honeck wrote:

Any theories here?

Loose connection or cold solder joint.

That was my first impression. It's been pretty humid around here.
Jim

"kontiki" wrote in message
...
Jay Honeck wrote:


Any theories here? I was hoping it would cure itself (ha!), but it
was the same on our flight today....
--

Could be moisture... it does interesting things to
little electronic circuits. The display on my Kx155
can do the same thuing for 30 seconds or so when
I first turn it on when in very humid weather.

What's the bus voltage like? The first sign of a low voltage
situation on several planes I flew was that the KX155 displays
started losing segments.

Hmmm. I didn't notice anything amiss, but I can't tell you exactly
(despite having not one, but TWO digital volt/amp meters in the
panel). I'll check that next time we fly.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

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

wrote:

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


If that fails, try time-honored diagnostic #2: unplug the unit and plug it
back in to reseat the connectors.

--
Dan
T-182T at BFM

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

If that fails, try time-honored diagnostic #2: unplug the unit and plug it
back in to reseat the connectors.

Well, I've tried whacking it (of course!), to no avail.

Luckily, my next planned upgrade was to install the outside air
temperature probe for the EDM-700, which will mean pulling the unit
out of the panel anyway. It's a real SOB to get at, so I suppose I
should be thankful that it chose now to go screwy...

Once it's out, we can play with it a bit more. I'm betting that I
have to send the danged thing back to JPI...
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"