Transponder Problem

The third digit on my formerly bullet-proof Narco AT-50 transponder has
suddenly started displaying incorrectly for ATC. Specifically, it seems to
be showing as a "4" on their screens, regardless of what we dial it to in
the plane. Thus, instead of squawking "1200" when we're VFR, we're
squawking "1240"...

What could cause this? Any recommendations on repair versus replacement?

Thanks!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

I've been
told that manufacturer doesn't allow independent avionics technicians
to (legally) repair their products anymore for certificated
installations.

There are no independent avionics technicians. There are certified repair
stations who employ avionics technicians. If the repair station was doing
Narco repairs before Narco pulled the rug out from under all of them and so
still has the correct and current technical data, and some other celestial
bodies align properly, the repair station can still work on the Narco
transponder and return it to service. I know of at least two avionics shops
that can do this if asked, but they don't advertise it, and I think don't
really want to.

The original poster ought to send it back to Narco.

"Jay Honeck" wrote:

Any recommendations on repair versus replacement?

I can no longer imagine having a transponder with four knobs.

If you get one with sequential digital entry, you can leisurely scoff at all
the Usenet arguments about the dangers of flipping through 7XXX codes...

It's really a minor thing, but I also like the fact that my transponder
displays pressure altitude. When I need to know pressure altitude, it saves
me the trouble of futzing with the Kollsman knob.

Jay, you fly one of the greatest GA airplanes ever designed (except for its
notable lack of a pilot-side door), and it deserves nothing less than the
best.

http://www.garmin.com/products/gtx327/
http://www.bendixking.com/static/cat...ls.jsp?pid=142

"Craig Prouse" wrote:
If you get one with sequential digital entry, you can leisurely
scoff at all the Usenet arguments about the dangers of
flipping through 7XXX codes...

It's really a minor thing, but I also like the fact that my
transponder displays pressure altitude. When I need
to know pressure altitude, it saves
me the trouble of futzing with the Kollsman knob.

Jay, you fly one of the greatest GA airplanes ever
designed (except for its
notable lack of a pilot-side door), and it deserves
nothing less than the best.

http://www.garmin.com/products/gtx327/

Amen. Next to the autopilot, the Garmin 327 is the best thing I've put
in my airplane.
--
Dan
C172RG at BFM

I'm not sure where the Narco repairs are expensive myth started. I've had good
experiences with the Narco factory with everything they've repaired, which
includes a Nav122 on two occasions, an AT150 and a com111B. In each case the
repair bill was very reasonable, and the unit was also updated with all mods and
fully recertified, which usually won't happen with a field repair. The only
beef I had was with turn around time, which is 4-6 weeks unless you pay a
premium for fast turn. IIRC, the premium is about $100, which nearly doubles
the cost of the repairs I had done. They will also evaluate your unit for $90
and let you know what it will cost to repair, and if you do repair it, they
subtract the eval cost from the repair.

The sticking digit sounds like either a switch problem, or a problem with the
digital logic. Where it is not intermittent, it should be easy to find and
fix. I can't imagine that it would be all that expensive to fix, certainly not
the price of a reconditioned unit less the trade in on yours.

Neal wrote:

On Thu, 04 Sep 2003 03:28:51 GMT, "Jay Honeck"
wrote:

The third digit on my formerly bullet-proof Narco AT-50 transponder has
suddenly started displaying incorrectly for ATC. Specifically, it seems to
be showing as a "4" on their screens, regardless of what we dial it to in
the plane. Thus, instead of squawking "1200" when we're VFR, we're
squawking "1240"...

What could cause this? Any recommendations on repair versus replacement?


Likely a shorted semiconductor component... either an IC chip, or
perhaps even something simple as a diode. Given the name brand, you'll
probably have to send it back to the factory and pay nearly as much as
a reconditioned unit to replace a faulty $0.25 part in it. I've been
told that manufacturer doesn't allow independent avionics technicians
to (legally) repair their products anymore for certificated
installations.

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

"Dave Butler" wrote:
I've never used one of the pushbutton units, but I can imagine a
difficulty with them. With knobs, I can hold on to the knob in
turbulence while I'm setting the digit. With buttons, I would
think turbulence would cause you to hit the wrong
button. Is this just an imaginary difficulty?

The buttons are big enough on the Garmin 327 that it hasn't been a problem
for me, but I've never had to change a squawk in moderate or worse
turbulence.
Still, having used a button xponder, I would never want to go back to the
knob type.
--
Dan
C172RG at BFM

"Ray Andraka" wrote in message ...
I'm not sure where the Narco repairs are expensive myth started. I've had good
experiences with the Narco factory with everything they've repaired, which
includes a Nav122 on two occasions, an AT150 and a com111B. In

Not my experience with factory service on the Mark 12D+. The factory
price may have been reasonable, but they were slow, unable to provide
loaners in the interim, and the units had to be shipped back multiple times.
Not good on a working aircraft.

"Jay Honeck" wrote in message
news:Tjy5b.345829$o%2.158911@sccrnsc02...
The third digit on my formerly bullet-proof Narco AT-50 transponder has
suddenly started displaying incorrectly for ATC. Specifically, it seems
to
be showing as a "4" on their screens, regardless of what we dial it to in
the plane. Thus, instead of squawking "1200" when we're VFR, we're
squawking "1240"...

What could cause this? Any recommendations on repair versus replacement?

Thanks!
--

What a coincidence. My AT 150 pulled this stunt at the beginning of a trip
from Texas to Las Vegas about a week ago. In my case, the third digit
flipped back and forth between 5 and 1. The bad news is that it will likely
get worse, to the point where ATC can only see you part of the time. That
caused me to rethink flying into the very busy Las Vegas area, opting
instead to park it at Kingman, AZ. At least we got to see the Hoover Dam
again.

Anyway, the good news is that mine was fixed locally for $65.00. It was
described as being an "adjustment", but I forget what was adjusted. I could
look at the invoice to refresh my memory. While I'd love a pushbutton
Garmin, I'm too cheap to toss a fixable unit.

To save you a phone call, Narco factory service is $95.00 per hour plus
parts. 2 to 3 week turnaround. They have a factory reconditioned exchange
program for $595.00. Also a 2 to 3 week turnaround. I think there are
issues with replacing an AT 50 with a 150. Something about needing a 150R.

Let me know if you want details about where I got mine done.

Dick Meade

Narco also has a 10% off web coupon for service if the radio is sent by the
owner.

In the case of a Nav radio, you could get away with flying without the radio for
a few weeks. A transponder in busy airspace is another thing altogether. Ask
around at the local shops to see if you can find one that will look at it. Here
in the Northeast, I've had good luck with The Radio Shop, which is located at
Worcester Mass, for repairing Narco stuff. Like I said before, the shops will
generally only fix what is wrong; they won't bring the unit up to the latest mod
level, do a complete check on the unit, or warranty the entire unit.

If I was looking at a repair that cost near the value of the transponder, I'd
seriously consider getting a new mode S with plans to eventually connect it to a
MFD for traffic. I don't think I'd spring for a new mode C only at this point,
as I suspect we'll be getting gently nudged to go with mode S in the not to
distant future. Fortunately, yours does not sound like an expensive problem
(the tube is fine, it is the digital encoding that is the problem), just an
inconvenient one. If you are on good terms with a local shop, you might be able
to get a loaner while you send it in to Narco if your local shop can't fix it.

Dick Meade wrote:

"Jay Honeck" wrote in message
news:Tjy5b.345829$o%2.158911@sccrnsc02...
The third digit on my formerly bullet-proof Narco AT-50 transponder has
suddenly started displaying incorrectly for ATC. Specifically, it seems
to
be showing as a "4" on their screens, regardless of what we dial it to in
the plane. Thus, instead of squawking "1200" when we're VFR, we're
squawking "1240"...

What could cause this? Any recommendations on repair versus replacement?

Thanks!
--

What a coincidence. My AT 150 pulled this stunt at the beginning of a trip
from Texas to Las Vegas about a week ago. In my case, the third digit
flipped back and forth between 5 and 1. The bad news is that it will likely
get worse, to the point where ATC can only see you part of the time. That
caused me to rethink flying into the very busy Las Vegas area, opting
instead to park it at Kingman, AZ. At least we got to see the Hoover Dam
again.

Anyway, the good news is that mine was fixed locally for $65.00. It was
described as being an "adjustment", but I forget what was adjusted. I could
look at the invoice to refresh my memory. While I'd love a pushbutton
Garmin, I'm too cheap to toss a fixable unit.

To save you a phone call, Narco factory service is $95.00 per hour plus
parts. 2 to 3 week turnaround. They have a factory reconditioned exchange
program for $595.00. Also a 2 to 3 week turnaround. I think there are
issues with replacing an AT 50 with a 150. Something about needing a 150R.

Let me know if you want details about where I got mine done.

Dick Meade

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

Jay Honeck wrote:

What could cause this? Any recommendations on repair versus replacement?

This happened with my Bendix-King unit. My avionics tech fixed it as part of
my 91.413 check - no additional charge. It was a bench repair and took him
only a few minutes.

George Patterson
A friend will help you move. A really good friend will help you move
the body.