I'm building an extensive NMEA network aboard "Lionheart" for its
owner who likes to have 2 of all the toys. I encountered a problem
adding a Yeoman to interface the paper charts to the network,
yesterday, that might be a good idea for everyone to know about.......

We put off adding the Yeoman until the more important parts of the new
system were installed and running (autopilot, radar, sonars, chart
plotters, computer interface, NMEA multiplexer, gyro-compass, etc.).
I figured out that the Yeoman's plotting board had plenty of signal to
go through the mahogany lift lid on the Amel's nice chart table, so
dismounted it from its old foam lap plotting board and affixed it with
two industrial-strength double-sided foam tape strips to the bottom of
the cover. This part of the Yeoman works fantastic! It will even
read through the chart table and a whole chart book folded back onto
itself and set atop of it against the guiding fiddles to hold it fast.

However, trouble started when I connected the Yeoman's NMEA wires to
my existing NMEA network that scared me much when I found out what was
wrong. Suddenly, there was no network data coming from either the
Noland Engineering NMEA multiplexer....or if I changed my emergency
switch over to the Raymarine radar direct....it's was all DEAD.

I got out my trusty Radio Shack Logic Probe (buy one if you have a
network.....very easy to use to find dead data lines fast) and put it
to the Noland's TX output that supplies data without the notebook
computer being on. IT WAS HELD HIGH! ....not good. I disconnected
the Yeoman's leads and THERE WAS NO DATA STILL!....oh oh.....

Luckily, no damage was done. The Noland had simply latched to protect
itself and recycling the master power relay reset it to working again.
Hmm...something isn't right with that Yeoman......

Now with all the wires disconnected from my bruised NMEA network, I
put the logic probe on the Yeoman's input and output wires. YAAACK!
THE INPUT WIRES ARE HIGH.....BOTH OF THEM!! How can this be? This is
the INPUT, not the output! A reading with my DVM showed battery
voltage, 13.8V with no connection to them...both of them.

I've traced the input pin on the main processor board attached to the
plotting board and, though I don't have a schematic, I think I found
an input transistor that is toast. From what should be its base the
input pin is connected to to what should be its collector, I get a
diode one way and 287 OHMS IN REVERSE BIAS. From either base or
collector pad to what should be its emitter pad....it get
nothing...nada....toasted.

This is NOT a new Yeoman. It came off the old boat and it goes back
before I took over electronic engineering for this captain. Someone
must have connected NMEA IN A (+) to the battery at some point,
blowing this transistor................and almost blowing my new
network.......

I've emailed the B&G Yeoman experts and will let this thread know what
I find......

Moral - BEFORE HOOKING ANYTHING TO YOUR NMEA NETWORK IN OR OUT,
MEASURE THE I/O WIRES WITH A VOLTMETER ON THE RUNNING UNIT TO SEE IF
IT'S RUNNING! 13.8V IS NOT NICE!

Yeoman sure is a cool tool to keep that paper chart if I can get this
working.....(c;



Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?