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TDRs are pricey and not generally or commonly available. A cheaper way of
finding the type of "intermittent open" that bit John is to use an "analog"
volt-ohmmeter and use the ohmmeter function to check each wire, pin-to-pin
(one probe held to pin on one end of a particular wire and other probe held
to tip of pin on other end of wire harness.) Takes time to assure you get
on correct pins to check a particular wire.
- While holding probes (or have female or mail pin/jack ends on your
test leads so you can slip the probes onto the pins/into the receptacles),
wiggle the wiring harness while watching the needle of the ohmmeter. If it
wiggles, you have an intermittent/bad connection, usually at a pin in one
connector or the other.
TDR is really good for LONG wires, for example, from avionics bay in an A-7
(or F-16) back to components in the tail end of the aircraft, going thru
several connectors on the way. It is really nice to know approximately
where the break is.
David
----- Original Message ----- From: "Dale Rogers" <dale.r@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, June 04, 2005 10:21 PM
Subject: [FlyRotary] Re: EC2 problems - solved
FWIW, if you think you have such a problem, finding someone
with a Time Domain Reflectometer (TDR) can save a lot of troubleshooting
time. Check an open-circuit wire from each
end. If the reading is different, you have a bad wire. The
time signature can even tell you how far down the wire the
break (or even partial break) is.
Dale R.
> From: Bob White <bob@bob-white.com>
> Date: 2005/06/04 Sat PM 07:27:31 EDT
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] Re: EC2 problems - solved
>
> Congratulations John,
>
> What a relief it must be to actually have an answer. A broken wire
> under the insulation is sometimes one of the hardest problems to find.
> It could have been worse. It could have worked till heat or vibration
> made it quit in flight.
>
> Bob W.
>
> On Sat, 4 Jun 2005 15:40:43 -0400
> "John Slade" <sladerj@bellsouth.net> wrote:
>
>> Tracy and others.
>> Following more than 12 months of battling with EC2 issues I'm pretty
sure
>> it's Eureka day!
>> After rewiring and testing for almost 4 weeks I plugged the EC2 in last
>> night, and got exactly the same symptoms as before. NOP flashing
indicating
>> no communication. I took the EC2 to Buly's plane and tried it in his
>> installation. Same NOP, so I was thinking I'd fried it again. Before
sending
>> it back yet again I decided to install it my plane one more time and
see if
>> there was a spark.
>>
>> To my amazement it worked. No NOP, and I could bring up the EC2 data.
The
>> only thing that changed overnight was that I moved the cable to unplug
it. I
>> climbed in the back and found that I could make the NOP flash, or stop
>> flashing, by moving the cable. I haven't taken the connector apart yet,
but
>> I'm expecting to find a broken wire inside the insulation, probably
near a
>> solder joint at the pin. Whenever I bent the connector outward for
testing
>> it made contact. When I bent it back to plug it in, contact was lost.
>>
>> Bingo!
>> John
>>
>> Just guessing, but maybe the new EC2 can't communicate with a
pre-autotune
>> EM2 like Buly's. ???
>> Homepage: http://www.flyrotary.com/
>> Archive: http://lancaironline.net/lists/flyrotary/List.html
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