Today's Message Index:
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1. 09:45 AM - Re: Garmin transponder power problems (Jeff Luckey)
2. 10:33 AM - Re: Garmin transponder power problems (Coastflyer)
3. 12:04 PM - Re: Re: Garmin transponder power problems (Jeff Luckey)
4. 02:44 PM - Re: Re: Garmin transponder power problems (Robert L. Nuckolls, III)
5. 11:39 PM - RF Interference (B Tomm)
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Subject: | Re: Garmin transponder power problems |
CoastFlyer,
Is there a possibility of a thermal event? I don't have any experience w/ t
he GTX 327 but I wonder if it has some kind of thermal shutdown feature.=C2
- The symptoms you describe might fit that profile:=C2- it gets hot, ha
s a thermal shutdown event, and then when it cools, it re-starts.
Is it:1. mounted in a closed-in box?
2. located next to some other piece of equipment that gets hot?3. does the
event happen more often on warmer days?
Other things (off the top of my head):4. the dreaded loose connection in th
e power wiring
5. flakey circuit breaker or avionics master switch
I had a situation a year back, where my whole avionics stack would shut dow
n intermittently & rarely - long story short, it was a loose connection on
the avionics master.
-Jeff
On Sunday, April 10, 2016 8:22 AM, Coastflyer <jessejenks72@gmail.com>
wrote:
com>
I've had a garmin transponder in my plane for the last 5 years. I bought it
new. I think it's a GTX 327. For the past couple years it will randomly po
wer off and back on. When it does this it is usually just momentary, someti
mes staying off for up to 30sec.
I checked the ground and power, and re racked it. I asked several avionics
shops about it with no results. At this point I guess I'm just going to shi
ne it until I'm required to buy an ads-b transponder unless anyone here has
a suggestion.
Thanks
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=454787#454787
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
-
S -
-
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
Message 2
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Subject: | Re: Garmin transponder power problems |
Jeff,
Thanks for the reply. I had wondered about overheating and asked the avionics shop
that question. The guy said it shouldn't be an issue with that transponder.
I have put my hand under the panel many times to see if it's getting hot, and
haven't felt anything alarming. I don't have a cooling fan though, and it is
stacked below my com radio, but that's it.
I guess I should go through the wiring again, because it sure does seem like a
bad connection somewhere. Also maybe worth calling garmin to see if they have
any input. I would be hesitant to send it in though because I could see getting
a big repair bill with a diagnosis of "tests ok on the bench.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=454840#454840
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Subject: | Re: Garmin transponder power problems |
"I would be hesitant to send it in though because I could see getting a big
repair bill with a diagnosis of "tests ok on the bench."
Agree.=C2- I have heard others complain about Garmin's flat-fee of $800 f
or GNS-430 test/repair. (Although I have no personal knowledge).=C2- Migh
t be different for your xponder.
On Monday, April 11, 2016 10:53 AM, Coastflyer <jessejenks72@gmail.com>
wrote:
com>
Jeff,
Thanks for the reply. I had wondered about overheating and asked the avioni
cs shop that question. The guy said it shouldn't be an issue with that tran
sponder. I have put my hand under the panel many times to see if it's getti
ng hot, and haven't felt anything alarming. I don't have a cooling fan thou
gh, and it is stacked below my com radio, but that's it.
I guess I should go through the wiring again, because it sure does seem lik
e a bad connection somewhere. Also maybe worth calling garmin to see if the
y have any input. I would be hesitant to send it in though because I could
see getting a big repair bill with a diagnosis of "tests ok on the bench.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=454840#454840
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
-
S -
-
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
Message 4
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Subject: | Re: Garmin transponder power problems |
>I guess I should go through the wiring again, because it sure does
>seem like a bad connection somewhere.
A test I've used on occasion is to supply the
victim device with a new power source. In the case
of a transponder, it can be a 20AWG wire with a
source-end 7A fuse tied to any handy hot-spot
on the power distribution system.
Cut into the victim's power wire(s) in a
handy location, strip the radio end and splice
the flying power lead to this exposed conductor.
This is a flight-worthy 'modification' that
can remain in place until you're sure that
the intermittent condition has or has not
repeated.
Bob . . .
Message 5
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Here's a challenge for the brains.
Suddenly my fuel pressure indication has become the victim of RF
interference. I've had the airplane off-line for some mods and upgrades and
during this time has come down with a severe case of RF-itis.
Symptoms:
When I push the PTT, the fuel pressure indication steadily climbs as a rate
of about 5 psi/second as long as it's maintained all the way to 60 PSI
(engine and fuel pump off). This occurs with either comm radio (each has
it's own antenna, feed line and routing), although one radio only gets the
error up to about 30-40 PSI. A handheld has a similar effect but to a
lesser degree presumably because it has less transmit power.
Note; ATC has no problem hearing my transmissions with either radio.
Things that I have changed since taking the airplane off-line when
everything had been working fine:
A) Replaced one comm antenna (bent whip on fuselage bottom) with a new
straight antenna installed on the rear turtle deck. This required extending
the coax with BNC and RG400 cable. This is the radio/antenna combination
that has the lesser effect on the fuel pressure reading. The other
radio/antenna system was not modified in any way. This radio has the larger
effect on the fuel pressure reading.
B) Added a VHF tracker radio which transmits a "bread-crumb" every 120
seconds.
C) The engine monitor was sent to the factory for a software upgrade that
wasn't needed after all and therefore nothing was done and re-installed.
Equipment:
A) The fuel pressure sender is GRT's HPS-SS-01 which has three wires and a
4th (shield) not to be connected. Details here...
http://www.grtavionics.com/documents/EIS/100%20psi%20SS%2012V%20Pressure%20S
ensor.pdf
I suspect this transducer has some electronics inside that are possibly
affected by RF in turn sending an erroneous reading out to the engine
monitor.
B) Engine monitor is GRT's EIS 4000.
What I have done so far...
A) Installed ferrite cores (6 so far) around all the wires coming out of the
sender, at the sender. This has caused the RF interference to be
dramatically reduced to a 4-6 PSI change (depending on which radio) while in
the hangar, but in the air, the interference still steadily climbs with
application of PTT. The output voltage on the signal wire (disconnected
from the engine monitor) sits idle at 1 volt but climbs steadily to over 4
volts with PTT/RF. The ferrite cores hold the voltage rise to about 200 mV.
B) I spoke to tech support at GRT today. They said if anything, put the
ferrite core around just the sender's signal wire where it goes into the
engine monitor. I installed one ferrite core there today (leaving all the
others in place) and this had no noticeable effect in the hangar. I think
the RF is affecting the sender, not the monitor.
C) The problem occurs whether the VHF tracker is turned on or not. I even
took the fuse out so this system has nothing connected to the power bus. I
have not removed the antenna however to see if it is somehow coupling the
comm's RF into the airframe via the ground wire. Is this possible? The
radio that has the largest effect has it's antenna closest to the tracker
antenna on the fuse bottom. The VHF tracker works as advertised.
Questions:
What is going on here?
Is it likely to be a sender has suddenly gone bad?
What about that shield wire that comes out of the sender that is not to be
connected to anything? What good is it if not connected to anything? The
wiring is not shielded between the sender and the engine monitor. The
sender's wiring was not modified in anyway during the aircraft's upgrades.
Is the Tracker's antenna feeding RF back into the airframe?
Any other ideas?
Bevan
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