I'm Going In... Radio Saga Continued...
three-eight-hotel
Narco radio's:
http://groups.google.com/group/rec.aviation.owning/browse_frm/thread/981307ec4df68cc6
I've decided that I'm going to pull the radio and the connector tray
and run new coax from the radio to the antenna, after cleaning every
contact point I can find with contact/connector cleaner. I figure the
worst case scenario is that I will have spent $20 - $30 for cable,
which is far less than taking it into an avionics shop for more
troubleshooting! Been there, done that!
I've pulled the radio out several times during troubleshooting, but
never paid attention to what would be entailed in pulling the connector
tray. For those who have done this before, is it going to be blatently
obvious when I get in, what needs to be done? Is it pretty
straight-forward, or am I going to be squeezing my head between the
rudder pedals and scraping my arm and knuckles on all of those hidden
dangers, lurking behind the panel?
Any tips or recommendations on how to pull the connector tray?
My thought on running coax is to do it as if I were pulling electrical
wire... Tape a new coax end, to the old coax end at the tray, and pull
from the antenna end to feed the new coax through. This way, I
shouldn't have to pull any plastic.
Any suggestions or lessons learned will be greatly appreciated!
Thanks and Best Regards,
Todd
RST Engineering
"three-eight-hotel" <to...@thepetersonranch.com> wrote in message
news:1128549847.7...@z14g2000cwz.googlegroups.com...
> I've posted twice before on the problems I have been having with my
> Narco radio's:
> http://groups.google.com/group/rec.aviation.owning/browse_frm/thread/981307ec4df68cc6
>
> I've decided that I'm going to pull the radio and the connector tray
> and run new coax from the radio to the antenna, after cleaning every
> contact point I can find with contact/connector cleaner. I figure the
> worst case scenario is that I will have spent $20 - $30 for cable,
> which is far less than taking it into an avionics shop for more
> troubleshooting! Been there, done that!
It may work. At the very least you will have new cable.
>
> I've pulled the radio out several times during troubleshooting, but
> never paid attention to what would be entailed in pulling the connector
> tray. For those who have done this before, is it going to be blatently
> obvious when I get in, what needs to be done? Is it pretty
> straight-forward, or am I going to be squeezing my head between the
> rudder pedals and scraping my arm and knuckles on all of those hidden
> dangers, lurking behind the panel?
The tray is generally held to the rack by four pan head or flathead screws.
If the installer was nice, he put rivnuts in the rack so all you have to do
is back the screws out. If he was not so nice, you wind up squeezing,
scraping, and bloodying getting a wrench into a LITTLE TINY gap in the rack
to hold the nut while you back the screw out.
DOn't even ASK about holding that nut when putting the tray back in. Come
to think of it, you won't have to worry about it because that nut will drop
right out of the wrench and become a permanent part of the weight and
balance ... not to be found until you pull negative g's and it relocates
itself between the master switch bus and ground.
>
> Any tips or recommendations on how to pull the connector tray?
>
> My thought on running coax is to do it as if I were pulling electrical
> wire... Tape a new coax end, to the old coax end at the tray, and pull
> from the antenna end to feed the new coax through. This way, I
> shouldn't have to pull any plastic.
Cut the new coax with a 45 degree angle on the coax and put the point of the
cut down so that it has a fighting chance to wedge itself rather than
butting up against a grommet of some sort. I myself prefer safety wire
instead of tape ... and I pull the safety wire through with the old coax
THEN the new coax. That way you aren't trying to pull double thicknesses of
coax through a single thickness space.
Jim
three-eight-hotel
That's what I was thinking...
>> The tray is generally held to the rack by four pan head or flathead screws.
>> If the installer was nice, he put rivnuts in the rack so all you have to do
>> is back the screws out. If he was not so nice, you wind up squeezing,
>> scraping, and bloodying getting a wrench into a LITTLE TINY gap in the rack
>> to hold the nut while you back the screw out.
I'll keep my fingers crossed and hope for the best
>> DOn't even ASK about holding that nut when putting the tray back in. Come
>> to think of it, you won't have to worry about it because that nut will drop
>> right out of the wrench and become a permanent part of the weight and
>> balance ... not to be found until you pull negative g's and it relocates
>> itself between the master switch bus and ground.
Now that's funny!!! LOL!
>> Cut the new coax with a 45 degree angle on the coax and put the point of the
>> cut down so that it has a fighting chance to wedge itself rather than
>> butting up against a grommet of some sort.
Will do... Thanks for that tip!
>> I myself prefer safety wire
>> instead of tape ... and I pull the safety wire through with the old coax
>> THEN the new coax. That way you aren't trying to pull double thicknesses of
>> coax through a single thickness space.
I was thinking something similar, it just seemed easier to explain it
that way...
Thanks for the feedback! I'm going to try and get to it Saturday and
thought I would probably get all of it done, except pulling the new
coax (don't have any yet). I could order the exact length I would
need, after I pull the old one.
Is there a reg on using RG-400 coax or can it be RG-58? I didn't see
coax on your site, but saw the connectors... Is that something that
can be ordered through RST, if I provided you with a length?
Thanks again!
Todd
TaxSrv
> I've decided that I'm going to pull the radio and the connector
> tray and run new coax from the radio to the antenna,
I've read your symptoms per your orig post, and you have one odd
collection of seemingly mutually-exclusive symptoms. If you can
xmit, but not receive, it's not the coax. Scratchiness, followed
by silence, isn't likely the connector, nor coax. Is that what it
still does? It sounds like a thermal fault in the squelch
circuitry. Narco uses a large fancy squelch circuit, squelching in
2 different ways and works on a hair trigger. Bad thermal behavior
of a component could cause grief. My Narco comm 120 does similar
and obviously a thermal, w/o the annunciating scratchiness.
Similar circuit; no time to pull and fix in such nice weather yet.
You can't pull the tray without dealing with the wires at the
connector. If you can do that, you can just visually inspect the
stuff for integrity. May take just an inspection mirror. I'd use
my $400 flexible, illuminated, magnifying boroscope. Next colon
cancer check, I'm using that to then check that doctor!
An avionics tech can visually check your connector from the front,
knowing what looks normal. He can maybe feel for integrity of the
wire connections from the back, having fondled hundreds. That's
why it's easy for him; hard for us.
For thermal, did you try flying w/o any box above and below the bad
one? That's how I know my 120's a thermal glitch.
Per other post, RG-400 will cure anything, nor do much
performance-wise at VHF.
Good luck!
Fred F.
George Patterson
> DOn't even ASK about holding that nut when putting the tray back in.
And since it's you doing the work, *you* will drill the holes out, borrow a
pop-rivet tool, and insert aviation quality rivnuts (like the original installer
should've done).
George Patterson
Drink is the curse of the land. It makes you quarrel with your neighbor.
It makes you shoot at your landlord. And it makes you miss him.
three-eight-hotel
>> collection of seemingly mutually-exclusive symptoms. If you can
>> xmit, but not receive, it's not the coax.
The weird symptom that goes along with the not receiving is the loss of
sidetone, when I attempt to xmit. That's the part that confuses me,
and leads me to question whether I can receive or not... Maybe I am
receiving, but just can't hear it??? I don't completely understand how
the radio, intercom and audio panel all tie together, so I'm confused
at the various symptoms I am encountering. i.e. a) clear side-tone
when talking over the intercom (no depression of the PTT) and able to
talk and listen to passengers. b) obviously clear transmission
(pressing PTT) but no sidetone and passenger doesn't hear me either.
(I say obviously clear because ATC acknowledged my transmission, which
I was able to confirm over a hand-held) c) Not hearing radio calls
(confirmed by listening and hearing them on a hand-held).
Sidetone is a function of the intercom, is it not? Meaning, if I were
to bypass the intercom and plug directly into the aircraft jacks (which
I have tried) I would not hear sidetone, when I attempted to transmit.
Either way, I was unable to hear known ATC coms while plugged directly
into the aircraft jacks.
>> Scratchiness, followed
>> by silence, isn't likely the connector, nor coax. Is that what it
>> still does?
It seems the first time it fails, it tends to fade out with
scratchiness. The last time I flew, I was able to turn the radio off
for a few seconds and turn it back on, to find it working for a minute
or two. This worked a few times, but failed to work, at all, the last
two times I tried it. The real pisser is that once I get it on the
ground, it seems to work fine!
>> It sounds like a thermal fault in the squelch
>> circuitry. Narco uses a large fancy squelch circuit, squelching in
>> 2 different ways and works on a hair trigger. Bad thermal behavior
>> of a component could cause grief. My Narco comm 120 does similar
>> and obviously a thermal, w/o the annunciating scratchiness.
>> Similar circuit; no time to pull and fix in such nice weather yet.
I just had the radio in for some questionable repairs at an avionics
shop that is a certified Narco dealer. They ran it up on the bench for
4 or 5 hours, and said that everything was within specifications... Is
this something a normal bench runup would be able to detect?
>> You can't pull the tray without dealing with the wires at the
>> connector. If you can do that, you can just visually inspect the
>> stuff for integrity.
At some point, before my last two flights, I crawled into that
wonderful position with my head between the rudder pedals and reached
my arm up behind the radio to see if I could feel anything out of the
ordinary (like I would know what ordinary felt like!). I grabbed at
the cables and wires and performed a wiggle-and-seat manuver for
everything I could blindly grab... My following two flights, each
nearly two hours, resulted in no radio failures. I was convinced the
problem was gone (okay, I was praying that the problem was gone).
However, the last two times I flew, it was back... This is when I
decided that I might have temporarily fixed something, but that
vibration had caught back up with me and undid what I fixed. My hope
was that removing and cleaning all connection points and making sure
everything is seated snugly when reinstalled, would fix my problem once
and for all. The worst case scenario is $20 of coax cable and pulling
back bloody stumps when I try to retrieve my arms from behind the
panel. If I take it to an avionics shop at this point, I will be
looking at a minimum of $300 to troubleshoot, and I have already dumped
nearly $600 for a questionable radio repair and a new antenna, while
shotgun troubleshooting.
>> For thermal, did you try flying w/o any box above and below the bad
>> one? That's how I know my 120's a thermal glitch.
I haven't tried that, but I did fly with a TKM slide-out loaner and
encountered a similar failure. I also put my radio in another plane
and the pilot reported that it did not fail during a nearly 3 hour
flight.
Above my radio is the audio panel, and below it is an ADF. The ADF is
inop, so I could remove it... Does the radio require the audio panel
to be useable in the airplane? Could I pull out the audio panel and
ADF, leave the radio in and plug my headsets into the aircraft (non
intercom) jacks and be able to xmit/receive? I'm willing to try
anything I can, to avoid throwing good money after bad! It would be
one thing if I could explain a set of symptoms to an avionics shop and
get an estimate to put this issue to bed, but I can't reproduce the
issue at will, unless a tech is willing to go flying with me! :-(
>> Per other post, RG-400 will cure anything, nor do much
>> performance-wise at VHF.
I don't completely follow this one??? RG-400 is or isn't necessary, as
opposed to RG-58?
Thanks for taking the time to respond!
Todd
Harvey
Hello. I have just arrived, so may be sticking my nose in, but this seems to
have narrowed it down quite a bit. If the radio was fine in another plane,
and another radio failed in yours, the radio is ok. It is your wiring in
your airplane. I agree it is not the antenna or coax. as this should affect
both tx and recieve. Jiggling yhe cables helped for a time. This is where I
would focus my time and money, I think.
Harvey
papenfus...@juneaudotmedotvt.edu
: The weird symptom that goes along with the not receiving is the loss of
: sidetone, when I attempt to xmit. That's the part that confuses me,
: and leads me to question whether I can receive or not... Maybe I am
: receiving, but just can't hear it???
Sidetone is, by definition, NOT the audio you hear when you receive. That's
the "received audio." Sidetone is you getting to hear yourself when you transmit.
I don't completely understand how
: the radio, intercom and audio panel all tie together, so I'm confused
: at the various symptoms I am encountering. i.e. a) clear side-tone
: when talking over the intercom (no depression of the PTT) and able to
: talk and listen to passengers.
The "sidetone" there is actually just the intercom functioning normally.
b) obviously clear transmission
: (pressing PTT) but no sidetone and passenger doesn't hear me either.
: (I say obviously clear because ATC acknowledged my transmission, which
: I was able to confirm over a hand-held)
So it has always transmitted properly?
c) Not hearing radio calls
: (confirmed by listening and hearing them on a hand-held).
: Sidetone is a function of the intercom, is it not? Meaning, if I were
: to bypass the intercom and plug directly into the aircraft jacks (which
: I have tried) I would not hear sidetone, when I attempted to transmit.
: Either way, I was unable to hear known ATC coms while plugged directly
: into the aircraft jacks.
Sidetone can be done in the intercom, the radio, or both. All it's doing is
looping back your mic signal into your own headset when the transmit button is down.
It just depends on how far up the chain you go before it loops back. When I installed
my intercom and coms, the intercom was initially wired to produce the sidetone.
I reconfigured the setup so that each radio provided its own sidetone. That way I
could ensure that all the signals were going all the way to the radios (and back to
me).
Here's something to think about based on my experience. Before we finished
the interior, we had a couple of intercom jacks in the back seats just zip-tied up,
but with bare 0.250/0.208 jacks wired in. Every once in awhile, they would move so
that in-flight the jacks would touch something aluminum. That would cause a really
ugly static, intermittent signal on the intercom if it hit a MIC wire. Between that
and the possibility of the intercom sharing multiple mics together, see if that adds
something to your debug equation.
: It seems the first time it fails, it tends to fade out with
: scratchiness. The last time I flew, I was able to turn the radio off
: for a few seconds and turn it back on, to find it working for a minute
: or two. This worked a few times, but failed to work, at all, the last
: two times I tried it. The real pisser is that once I get it on the
: ground, it seems to work fine!
"Fade out with scratchiness" sounds like it could be internal to the radio.
: >> It sounds like a thermal fault in the squelch
: >> circuitry. Narco uses a large fancy squelch circuit, squelching in
: >> 2 different ways and works on a hair trigger. Bad thermal behavior
: >> of a component could cause grief. My Narco comm 120 does similar
: >> and obviously a thermal, w/o the annunciating scratchiness.
: >> Similar circuit; no time to pull and fix in such nice weather yet.
: I just had the radio in for some questionable repairs at an avionics
: shop that is a certified Narco dealer. They ran it up on the bench for
: 4 or 5 hours, and said that everything was within specifications... Is
: this something a normal bench runup would be able to detect?
Neither the thermal stresses nor the vibration are adequately simulated by
letting the thing warm on the bench for 5 hours. Do you have active cooling and is it
in good shape? i.e. a fan or ram-air blowing on it?
Just a thought... not too likely.
: At some point, before my last two flights, I crawled into that
: wonderful position with my head between the rudder pedals and reached
: my arm up behind the radio to see if I could feel anything out of the
: ordinary (like I would know what ordinary felt like!). I grabbed at
: the cables and wires and performed a wiggle-and-seat manuver for
: everything I could blindly grab... My following two flights, each
: nearly two hours, resulted in no radio failures. I was convinced the
: problem was gone (okay, I was praying that the problem was gone).
: However, the last two times I flew, it was back... This is when I
: decided that I might have temporarily fixed something, but that
: vibration had caught back up with me and undid what I fixed. My hope
: was that removing and cleaning all connection points and making sure
: everything is seated snugly when reinstalled, would fix my problem once
: and for all. The worst case scenario is $20 of coax cable and pulling
: back bloody stumps when I try to retrieve my arms from behind the
: panel. If I take it to an avionics shop at this point, I will be
: looking at a minimum of $300 to troubleshoot, and I have already dumped
: nearly $600 for a questionable radio repair and a new antenna, while
: shotgun troubleshooting.
I hear you. Troubleshooting intermittent problems sucks. Another possibility
is wrong spacers on one or more trays. My mechanic had troubles with his transponder
and intermittent connections on an encoder line or two. After a bunch of rewires,
checking, etc, we discovered that some small nuts/washers were installed on the wrong
side of the connector on the back of the tray. It was preventing the connector from
seating an additional 1/8" and causing intermittent failures on a few pins.
: I haven't tried that, but I did fly with a TKM slide-out loaner and
: encountered a similar failure. I also put my radio in another plane
: and the pilot reported that it did not fail during a nearly 3 hour
: flight.
From that right there, it sounds like you can rule out your radio. Don't
discount multiple *different* failures in the debug equation. Maybe it's your audio
panel or intercom?
: Above my radio is the audio panel, and below it is an ADF. The ADF is
: inop, so I could remove it... Does the radio require the audio panel
: to be useable in the airplane?
Doesn't *need* it, but it's probably wired to use it. If you've got a set of
direct-to-radio heaset plugs, those should still work with the ADF and audio panel
out. It also likely doesn't change anything whether they're in or not, though.
Could I pull out the audio panel and
: ADF, leave the radio in and plug my headsets into the aircraft (non
: intercom) jacks and be able to xmit/receive? I'm willing to try
: anything I can, to avoid throwing good money after bad! It would be
: one thing if I could explain a set of symptoms to an avionics shop and
: get an estimate to put this issue to bed, but I can't reproduce the
: issue at will, unless a tech is willing to go flying with me! :-(
: >> Per other post, RG-400 will cure anything, nor do much
: >> performance-wise at VHF.
: I don't completely follow this one??? RG-400 is or isn't necessary, as
: opposed to RG-58?
: Thanks for taking the time to respond!
: Todd
RG-400 shouldn't really be necessary at VHF frequencies. The materials are
better, and it has better high-frequency characteristics (e.g. transponder or DME).
At VHF it primarily serves to be more of a PITA to work with (much more rigid). It
also screwed with my compass once because it had a copper/tin-clad steel center
conductor.
-Cory
--
*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
papenfus...@juneaudotmedotvt.edu
: "three-eight-hotel" wrote:
: > I've decided that I'm going to pull the radio and the connector
: > tray and run new coax from the radio to the antenna,
: I've read your symptoms per your orig post, and you have one odd
: collection of seemingly mutually-exclusive symptoms. If you can
: xmit, but not receive, it's not the coax.
Oh, and I forgot on my other post that I concur it's most likely NOT the coax.
That doesn't really cause scratchiness.... you either have signal or you don't.
Scratchiness is caused by the signal to from your mics or to your headset (or from
within the audio panel, intercom, or radio, which is pretty much ruled out at this
point, too).
three-eight-hotel
>> the "received audio." Sidetone is you getting to hear yourself when you transmit.
>>
That all pretty much makes sense to me...
>> So it has always transmitted properly?
I'm pretty sure it has... I recall one of my first failures, while
shooting ILS approaches at SAC. After minutes of trying to figure out
why ATC wasn't responding to me, I grabbed my handheld to find out that
they had been hearing me all along. However, at that time, I was
hearing sidetone while xmitting, just not hearing audio back.
>> Here's something to think about based on my experience. Before we finished
>> the interior, we had a couple of intercom jacks in the back seats just zip-tied up,
>> but with bare 0.250/0.208 jacks wired in. Every once in awhile, they would move so
>> that in-flight the jacks would touch something aluminum. That would cause a really
>> ugly static, intermittent signal on the intercom if it hit a MIC wire. Between that
>> and the possibility of the intercom sharing multiple mics together, see if that adds
>> something to your debug equation.
I'm considering opening all of the intercom jacks (two in front and two
in back) and visually inspecting the connectors and wires there too,
just for grins. I'll pull new wire for them, if I have to as well...
>> "Fade out with scratchiness" sounds like it could be internal to the radio.
That's a tough one, because I don't even know if I'm describing this
symptom well... It's very quick and is simply an indication that the
failure is occurring. It's not a long drawn out fade, and the
scratchiness is really more of a quick (but barely audible) static that
I hear, when the radio fails.
>> Neither the thermal stresses nor the vibration are adequately simulated by
>> letting the thing warm on the bench for 5 hours. Do you have active cooling and is it
>> in good shape? i.e. a fan or ram-air blowing on it?
Not that I am aware of???
>> I hear you. Troubleshooting intermittent problems sucks. Another possibility
>> is wrong spacers on one or more trays. My mechanic had troubles with his transponder
>> and intermittent connections on an encoder line or two. After a bunch of rewires,
>> checking, etc, we discovered that some small nuts/washers were installed on the wrong
>> side of the connector on the back of the tray. It was preventing the connector from
>> seating an additional 1/8" and causing intermittent failures on a few pins.
That 1/8" issue is one of the top things in my mind... I'm thinking
the whole exercise of pulling, cleaning and reinstalling may enable me
to get a proper seating, that may not be occurring now???
>> From that right there, it sounds like you can rule out your radio. Don't
>> discount multiple *different* failures in the debug equation. Maybe it's your audio
>> panel or intercom?
Possibly???
>> RG-400 shouldn't really be necessary at VHF frequencies. The materials are
>> better, and it has better high-frequency characteristics (e.g. transponder or DME).
>> At VHF it primarily serves to be more of a PITA to work with (much more rigid). It
>> also screwed with my compass once because it had a copper/tin-clad steel center
>> conductor.
That's good to know... The RG-58 is much cheaper!
Thanks to you, and to all for your input! I feel like Chevy Chase, in
Fletch, when I'm looking at this stuff! I'm pretty darn sure the whole
problem is in the Fetzer Valve... Now if I can just round up some
gauze and some ball-bearings, I think I might be able to get this
problem licked! ;-) Ohhh, and I'll have to clean the windows too,
because they've got "filth muck" all over them!
Todd
RST Engineering
Everybody here is trying to tell you the same thing in different words. You
have a "I'll just pull wire and everything will be all right" fetish. Get
over it. "Bad wires" have about as much chance for failure as "bad bolts".
My advice is to tune in a constant signal ... like an atis or awos and start
moving things around briskly. When the signal fails or comes back after
failure repeat the jiggle. Narrow down the jiggle area.
Jim
> I'm considering opening all of the intercom jacks (two in front and two
> in back) and visually inspecting the connectors and wires there too,
> just for grins. I'll pull new wire for them, if I have to as well...
>
three-eight-hotel
>> have a "I'll just pull wire and everything will be all right" fetish. Get
>> over it. "Bad wires" have about as much chance for failure as "bad bolts".
Okay, so I hear you... but I think where my fetish lies is not with
pulling new wires, but in making sure there is proper seating, in
anything and everything I can get to. If what I'm hearing is that Coax
and wires will have nothing to do with it, I will move on from that
thought. I was thinking corrosion, rust, ??? on a coax connector, or
connector anywhere (especially connector tray -> radio), for that
matter. Even you agreed that replacing the coax "may work" and that I
would only be out a couple of bucks, worst case. Your description of
cutting the coax at a 45 degree angle led me to think that you might be
questioning the coax "connector" to radio or antenna or at least be
keeping it on a list of suspects.
>> My advice is to tune in a constant signal ... like an atis or awos and start
>> moving things around briskly. When the signal fails or comes back after
>> failure repeat the jiggle. Narrow down the jiggle area.
I've been using the ATIS at SAC as my constant signal, and have been
forcefully pressing the radio in and shaking it from side to side to
see if I can get it to come in, so much so that the LED's dim on the
radio as I'm pushing it in. That's never got reception to come back.
As far as other things, which I assume you are talking about wires
behind the panel, I can certainly give that a try, once I can figure
out how to do that without putting my self into an unintentional
unusual attitude. I'm 6'2" and about 2 bucks, so I can barely get
behind the panel when the plane is parked safely on the ground, let
alone 5000 feet and 100 kts.
I REALLY do appreciate all of the input, and am not TRYING to be a
knuckle-head about all of this! I'm just trying to interplote the
input I am receiving and do things that are within my capabilities.
And in this case, my capabilities don't seem to cover a very broad
spectrum!
Thanks,
Todd
papenfus...@juneaudotmedotvt.edu
: Okay, so I hear you... but I think where my fetish lies is not with
: pulling new wires, but in making sure there is proper seating, in
: anything and everything I can get to. If what I'm hearing is that Coax
: and wires will have nothing to do with it, I will move on from that
: thought. I was thinking corrosion, rust, ??? on a coax connector, or
: connector anywhere (especially connector tray -> radio), for that
: matter. Even you agreed that replacing the coax "may work" and that I
: would only be out a couple of bucks, worst case. Your description of
: cutting the coax at a 45 degree angle led me to think that you might be
: questioning the coax "connector" to radio or antenna or at least be
: keeping it on a list of suspects.
Coax isn't all that hard to replace, necessarily... BUT it can be a big pain
to route. It goes all the way to the antenna... likely a fairly long way. Soldering
the ends on (well) requires a pretty good knowledge of a soldering iron... not just
"which end to grab." :) Given that it's very unlikely to be that particular one, I'd
start with something else.
: >> My advice is to tune in a constant signal ... like an atis or awos and start
: >> moving things around briskly. When the signal fails or comes back after
: >> failure repeat the jiggle. Narrow down the jiggle area.
: I've been using the ATIS at SAC as my constant signal, and have been
: forcefully pressing the radio in and shaking it from side to side to
: see if I can get it to come in, so much so that the LED's dim on the
: radio as I'm pushing it in. That's never got reception to come back.
: As far as other things, which I assume you are talking about wires
: behind the panel, I can certainly give that a try, once I can figure
: out how to do that without putting my self into an unintentional
: unusual attitude. I'm 6'2" and about 2 bucks, so I can barely get
: behind the panel when the plane is parked safely on the ground, let
: alone 5000 feet and 100 kts.
The problem my mechanic's transponder had couldn't be induced by forcing the
radio around in the tray. It was a mechanical stop near the connector. Couldn't
really make it come and go. Of course it was further complicated by the fact that the
only way to check it was to test-fly it and ask local ATC if they could read ModeC (I
don't have a transponder interroagtor). For your COM, it should be easier.
Just as a thought... have you tried pulling out the squelch when you're unable
to receive? If you don't hear static when you can't receive, it's likely in the
wiring/connector from the radio/intercom/audiopanel/jacks. If you hear static but you
still cannot receive, then it's much more likely the radio.
: I REALLY do appreciate all of the input, and am not TRYING to be a
: knuckle-head about all of this! I'm just trying to interplote the
: input I am receiving and do things that are within my capabilities.
: And in this case, my capabilities don't seem to cover a very broad
: spectrum!
The biggest thing would be to try and make it happen on the ground so that you
can troubleshoot it. I'm not familiar with Narco's trays, but on the King ones, the
connector can be disconnected from the tray. Then you could play with that without
being stuck with the geometry of the tray. Basically, stop at the top and work
down...
RST Engineering
I was thinking corrosion, rust, ???
Rust is iron oxide and will only form on iron or steel. Corrosion is a
different matter, but you can rub or spray corrosion off. The only way coax
deteriorates is in sunlight or with water inside the shield. Age is a
second order factor.
on a coax connector, or
> connector anywhere (especially connector tray -> radio), for that
> matter. Even you agreed that replacing the coax "may work" and that I
> would only be out a couple of bucks, worst case.
Yeah, as well as throwing salt over my left shoulder has kept me from being
trampled by hippopotami all my life, but I don't think replacing the salt
shaker is going to have any effect.
Your description of
> cutting the coax at a 45 degree angle led me to think that you might be
> questioning the coax "connector" to radio or antenna or at least be
> keeping it on a list of suspects.
No, I was telling you to do that so the square-cut coax wouldn't hang up on
the grommets as you pulled it.
>
>>> My advice is to tune in a constant signal ... like an atis or awos and
>>> start
>>> moving things around briskly. When the signal fails or comes back after
>>> failure repeat the jiggle. Narrow down the jiggle area.
>
> I've been using the ATIS at SAC as my constant signal, and have been
> forcefully pressing the radio in and shaking it from side to side to
> see if I can get it to come in, so much so that the LED's dim on the
> radio as I'm pushing it in.
Do you intend to destroy your radio in the fixit process?
That's never got reception to come back.
> As far as other things, which I assume you are talking about wires
> behind the panel, I can certainly give that a try, once I can figure
> out how to do that without putting my self into an unintentional
> unusual attitude. I'm 6'2" and about 2 bucks, so I can barely get
> behind the panel when the plane is parked safely on the ground, let
> alone 5000 feet and 100 kts.
You CANNOT do troubleshooting at 5K and speed. You HAVE to do it on the
ground. THe easy way is to pull the front seats out and lay on the floor.
I'm 6-3 and two and a quarter, and this is the only way I can troubleshoot
any airplane except a heavy with a radio rack in the belly.
>
> I REALLY do appreciate all of the input, and am not TRYING to be a
> knuckle-head about all of this! I'm just trying to interplote the
> input I am receiving and do things that are within my capabilities.
> And in this case, my capabilities don't seem to cover a very broad
> spectrum!
You need to get the airplane to a place where you can get at the radio with
a constant signal. You also need access to tools and such when you DO find
the problem. I think I've got an old com test set around here somewhere
that radiates a constant low level signal on 122.8, powered by a 9 volt
battery. If you'd like to come up to Grass Valley and borrow it, I'd be
glad to loan it to you ... if I can find it.
Jim
TaxSrv
loss of
> : sidetone, when I attempt to xmit.
I'm gettting a bit lost in facts and symptoms here. Anyway, we
must bypass intercom to isolate to which box. If the Narco, it
does not know receive audio from sidetone in the circuit area of
interest, if both those signals are absent.
There's audio leveling circuitry in there to which both mic audio
and receive audio are fed. The nature of that circuit is such that
component drift through heat upsets a delicate balance, and there's
many analog swith ICs in there to turn things on and off. The fact
that you can xmit w/o hearing mic audio I believe may isolate the
fault to a certain area of that circuit.
If true that it works for a while and then stops, that's gotta be
thermal. A wire or coax connection can theoretically behave like
that, but airplanes vibrate. The thermal expansion of metal is
like what in comparison? The only wire connection for your
symptoms should be phone audio out from the comm.
The reason I'm leaning in this direction is that there are simpler
circuits in comm boxes where all your symptoms could not happen.
In the Narco design it can; it's an electronic Rube Goldberg
machine. And the only company on earth who still write code for
the MK3870 CPU chip.
Fred F.
N93332
for the coax cable connection? Can you try a piece of short coax connected
to a 'portable' antenna attached to some type of ground plane? If this setup
works, then you'll know it's somewhere in the original coax connections, if
the radio still doesn't receive, then it would be a different connection
problem.
Are you sure the radio itself is good?
If you have already tried this, disregard...
three-eight-hotel
Last night, I went up to the airport and pulled out the radio, and
pulled the connector tray as far out/forward as I could. I performed a
close visual inspection and noticed something that I hadn't noticed
before... The radio and connector union seems to be made through two
24 pin connectors and two BNC connectors. The BNC connectors are an
opposing male and female (one each on the tray, and one each opposing
on the radio). What I noticed (forgive any improper terminology) is,
that the male connector on the tray seemed to be missing one tooth (for
lack of a better word) on the outer ring of the connector and the
radio, seemed to be lacking two teeth, on the outer ring of it's male
BNC connector (that's almost half!)
Aside from not being a good thing, is this a likely suspect for some of
the symptoms I have been experiencing? Replacing those two male BNC
connectors would seem like good common sense, but is this just an
unfortunate coincidence of something else being found while
troubleshooting another problem?
Look... I'm admittedly a couple of bricks short of a fireplace, when
it comes to talking circuitry and componentry, so no piling on! ;-)
I've been paying attention to all of the posts, but alot of it seems to
be going over my head. It's not like I'm not listening... I promise,
I'm not going to go pulling any wire!
I may, however, take you up, Jim, on a trip to Grass Valley to borrow
your constant signal device or bird watt meter you mentioned in a
previous post. One step at a time, though, I guess...
Thanks,
Todd
TaxSrv
> ... the male connector on the tray seemed to be missing one
> tooth (for lack of a better word) on the outer ring of the
> connector and the radio, seemed to be lacking two teeth, on
> the outer ring of it's male BNC connector (that's almost half!)
>
> Aside from not being a good thing, is this a likely suspect for
> some of the symptoms I have been experiencing?
Whatever's goin' on there will not cause a loss of sidetone.
Fred F.
three-eight-hotel
I pulled everything from the stack this weekend and visually inspected
everything I could see... As mentioned in a previous response, every
single screw, holding in every tray, had a nut on the back of it, and
half of them became part of the permanent W/B! I took an air
compressor with me, along with the component/connector cleaner and
cleaned every connection I could. I'm going to hold off on putting the
trays back in and borrow the tools from my mechanic to do it right,
rather than figure out how I'm going to hold nuts on the back of trays
for each screw.
While I was working on this, I ran into someone up at the Ghost-town
(err, I mean Georgetown) airport that I haven't seen in a while. He
offered to let me swap out and try his audio panel, to see if that
might be the culprit! As soon as I get the trays back in place and can
reseat all of the avionics devices, I'll give it a quick check flight
to see if I can get it to fail again, then try the replacement audio
panel.
Thanks for all of the responses, and I'll provide an update when I can.
Best Regards,
Todd
Ross Richardson
went back to the factory. It is fixed and working fine. The side tone is
a product of the radio not the audio panel. How I isolated it was
swapping the two MK12Ds I had and the problem followed the radio.
Therefore not in the trays, coax, audio panel, etc.
-------------
Regards, Ross
C-172F 180HP
KSWI
TaxSrv
> I'm going to hold off on putting the
> trays back in and borrow the tools from my mechanic to do
> it right, rather than figure out how I'm going to hold nuts on
> the back of trays for each screw.
You mean to borrow his trained mouse, or his JB Weld to epoxy the
nut in place? Sight unseen, that's what I'd do if workable. What
are the screws affixing, the tray or the connector?
Fred F.
George Patterson
> You mean to borrow his trained mouse, or his JB Weld to epoxy the
> nut in place?
I'd put in rivnuts (as Jim suggested). There's entirely too much danger of
epoxying the bolt into the nut.
If you do go the epoxy route, buy a bunch of nylon bolts and use those to hold
the nuts in place while the epoxy cures. If any of the bolts gets glued in, they
can be removed with a drill and tap pretty easily.
three-eight-hotel
With all of the symptoms I have been having and troubleshooting reports
I have provided, I'm surprised anyone can follow these posts, because
I'm having a hard enough time myself! ;-)
In a previous post, I reported that I had swapped out my radio with a
known working TKM replacement radio, and encountered a failure with
that radio as well. I also let my instructor throw my radio in another
plane, for a lesson she was giving, and she reported back that my radio
worked the whole time. I also took the radio in to a Narco dealer and
they ran it up on the bench for several hours and said that everything
was within specifications. This, however, after they made a
questionable repair only weeks earlier!
Based on the TKM's failing in my plane, and my radio working in another
plane, it seems unlikely that it is in the radio, but not impossible.
I could easily be experiencing one set of coincidences after another!
"The side tone is a product of the radio not the audio panel",
perplexes me though... Reception loss and sidetone loss at the same
time is the current prevolent symptom. At the occurence of failure, I
have reception loss and sidetone loss, I do have sidetone going
through the intercom though, as I can communicate with the passengers
fine. It is only on xmit where I lose sidetone... Plugging into the
aircraft jacks directly doesn't help because if I understand correctly,
you wouldn't get sidetone there anyways. Sidetone in that respect is a
product of the intercom, is it not? So... there are three components
(radio, intercom, audio panel) that are all interconnected somehow, and
that's where my eye's glaze over and I start to drool... I just don't
get it???
Are there any recommended readings out there, that anyone could
recommend to at least bring my up to a third grade level on this stuff?
A search for "avionics for dummies", came up goose eggs!
Thanks again for your responses!
Todd
three-eight-hotel
>> epoxying the bolt into the nut.
That's what I'm hoping for... I'll have to see what he has available
and make due with what I can.
To answer Fred's question, the screws are affixing the trays... I'd
use his mouse, but the poor thing was helping hand prop an old Piper
Cub, a couple of months ago, and wasn't following proper procedures...
If you've ever seen a rodent penetrate a sheet metal hanger door, you
wouldn't be surprised if I told you it was quite a mess!
Tauno Voipio
The intercom and sidetone go different ways:
- the intercom connects the amplified mic signal directly to the
all the headphones,
- the sidetone is created inside the COM radio by receiving
the transmitted signal with a simple detector and feeding
the signal to the headphone line.
If the sidetone is missing, either the audio path is broken or
the radio does not transmit properly. There is a slight possibility
that the sidetone receiving circuit is the culprit, but it's so
simple that the probability is tiny.
Assuming that the radio behaves in another plane, I see the
possible causes:
- the power supply to the radio is flaky,
- the microphone signal path to the radio is flaky,
- the audio output path from the radio is flaky, or
- the antenna connection is broken / shorted.
The simultaneous loss of reception and sidetone kind of
drop the microphone from the cause list above, the others
are still relevant.
HTH
--
Tauno Voipio (OH-PYM)
tauno voipio (at) iki fi
three-eight-hotel
>> The intercom and sidetone go different ways:
>>
>> - the intercom connects the amplified mic signal directly to the
>> all the headphones,
>>
>>
>> - the sidetone is created inside the COM radio by receiving
>> the transmitted signal with a simple detector and feeding
>> the signal to the headphone line.
So, feeding the signal to the headphone line would automatically send
the signal to all headphones on the intercom unless the intercom was in
Pilot ISO mode, if I understand correctly? I'm assuming this, since
the passengers can typically hear the radio calls I make. When I lose
sidetone (and reception), the passengers can't hear my xmissions
either, indicating, based on your response, that the signal is never
being fed out of the COM radio (or possibly the signal isn't even
getting to the COM radio). Am I catching on?
>> Assuming that the radio behaves in another plane, I see the
>> possible causes:
>>
>> - the power supply to the radio is flaky,
>> - the microphone signal path to the radio is flaky,
>> - the audio output path from the radio is flaky, or
>> - the antenna connection is broken / shorted.
>>
>> The simultaneous loss of reception and sidetone kind of
>> drop the microphone from the cause list above, the others
>> are still relevant.
If the power supply to the radio was an issue, would that be evident in
the radio itself, such as led's dimming or loss of power? I never seem
to notice a visible issue with power, and if it's relevant, the NAV
side of the radio never seems to fail at all. I always have constant
indication of a tuned in VOR, regardless of issues I am having on the
COM side.
This loss of reception and sidetone is ALWAYS simultaneous, so I'll
skip the microphone issue.
"The audio output path from the radio"... Would this be a coax cable
from the radio to the intercom? I recall seeing a box (2"x4" or so),
separate from the intercom, with coax from the radio to it... I tried
to trace where the coax went from there, but it seemed to be buried
deep inside a nest of other wires, so I gave up on trying to follow it.
If the radio behaves in another plane, I am assuming you are talking
about an audio output path that is not a part of the radio. So...
somewhere between the radio and the intercom then???
"The antenna connection is broken/shorted" - I'm a little confused at
the likelyhood of this, because what I seem to be hearing in this and
previous posts is that the loss of sidetone likely rules out a
connection between the radio and the antenna. Maybe I'm not catching
on? ;-)
Slowly but surely, I think I'm getting it, but I still think one of you
guys could make a lot of money on an Avionics for Dummies book! I'd
buy it! ;-)
Thanks for your feedback!
Todd
papenfus...@juneaudotmedotvt.edu
: went back to the factory. It is fixed and working fine. The side tone is
The sidetone can usually be set up either way (radio or intercom).
papenfus...@juneaudotmedotvt.edu
: plane, it seems unlikely that it is in the radio, but not impossible.
: I could easily be experiencing one set of coincidences after another!
Sounds like you've pretty much removed the radio from the equation.
: "The side tone is a product of the radio not the audio panel",
: perplexes me though... Reception loss and sidetone loss at the same
: time is the current prevolent symptom. At the occurence of failure, I
: have reception loss and sidetone loss, I do have sidetone going
: through the intercom though, as I can communicate with the passengers
: fine.
"Sidetone" generally refers to hearing what you are transmitting on the radio,
not what you are saying on the intercom. One could argue it's a pedantic difference,
but for what you are troublshooting, the difference is important.
It is only on xmit where I lose sidetone...
Correction: It's only when you transmit that you should *HAVE* sidetone.
Any other time your "sidetone" is simply the intercom intercom'ing.
Plugging into the
: aircraft jacks directly doesn't help because if I understand correctly,
: you wouldn't get sidetone there anyways. Sidetone in that respect is a
: product of the intercom, is it not?
It could be on the intercom, on the radio, or *both*, depending on how
whomever installed it decided to wire it up.
So... there are three components
: (radio, intercom, audio panel) that are all interconnected somehow, and
: that's where my eye's glaze over and I start to drool... I just don't
: get it???
: Are there any recommended readings out there, that anyone could
: recommend to at least bring my up to a third grade level on this stuff?
: A search for "avionics for dummies", came up goose eggs!
Trouble is that there is no "one true way" to install the stuff. There are
generally enough connections included in all of the devices that there are different
ways to accomplish the same thing.
Judging by your statement here:
:Reception loss and sidetone loss at the same
: time is the current prevolent symptom. At the occurence of failure, I
: have reception loss and sidetone loss, I do have sidetone going
: through the intercom though, as I can communicate with the passengers
: fine.
I'd say you've got a bad connection between the "audio out" of the radio and
the COM[12] on the audio panel, or between the audio panel and the intercom. I would
also speculate that the intercom is not producing sidetone, but the radio is... thus
the loss of sidetone upon transmit, but the intercom remains functional.
I don't specifically remember other details that may contradict this idea, but
I'm sure they'll be pointed out to me by someone... :)
-Cory
papenfus...@juneaudotmedotvt.edu
: the signal to all headphones on the intercom unless the intercom was in
: Pilot ISO mode, if I understand correctly? I'm assuming this, since
: the passengers can typically hear the radio calls I make. When I lose
: sidetone (and reception), the passengers can't hear my xmissions
: either, indicating, based on your response, that the signal is never
: being fed out of the COM radio (or possibly the signal isn't even
: getting to the COM radio). Am I catching on?
Ah... you gotta be careful when you talk about intercoms. Sometimes they do
some funky relay switching when the XMIT is hit. What it's probably doing (even when
not in pilot ISO mode) is that it's disabling the intercom circuit. At the same time,
it's routing the pilot MIC to the radio, but routing the sidetone (that is generated
by the RADIO, not the intercom) out to all the pax's headsets. ... or at least that's
what's supposed to be happening.
As if that wasn't complicated enough, a flaky relay inside the intercom could
cause all sorts of spastic and seamingly unrelated failures between XMIT and non-XMIT.
: If the power supply to the radio was an issue, would that be evident in
: the radio itself, such as led's dimming or loss of power? I never seem
: to notice a visible issue with power, and if it's relevant, the NAV
: side of the radio never seems to fail at all. I always have constant
: indication of a tuned in VOR, regardless of issues I am having on the
: COM side.
Not likely given the swap-out... radio is likely blameless.
: "The audio output path from the radio"... Would this be a coax cable
: from the radio to the intercom? I recall seeing a box (2"x4" or so),
: separate from the intercom, with coax from the radio to it... I tried
: to trace where the coax went from there, but it seemed to be buried
: deep inside a nest of other wires, so I gave up on trying to follow it.
: If the radio behaves in another plane, I am assuming you are talking
: about an audio output path that is not a part of the radio. So...
: somewhere between the radio and the intercom then???
The audio output path from the radio is usually a "coax"... actually, a small
shielded aircraft wire... definately NOT an antenna-looking RG-58-type wire.
: "The antenna connection is broken/shorted" - I'm a little confused at
: the likelyhood of this, because what I seem to be hearing in this and
: previous posts is that the loss of sidetone likely rules out a
: connection between the radio and the antenna. Maybe I'm not catching
: on? ;-)
Antenna likely vidicated before.
: Slowly but surely, I think I'm getting it, but I still think one of you
: guys could make a lot of money on an Avionics for Dummies book! I'd
: buy it! ;-)
The bitch of the avionics installs is getting the damn information you need.
With install manuals for everything, it's usually pretty straight-forward. Without
them, you're flying blind most of the time and things get mis-installed.
TaxSrv
> I'd put in rivnuts (as Jim suggested). There's entirely too much
danger of
> epoxying the bolt into the nut.
>
That's indeed Murphy's Law, but I'm assuming a 6 or 8-32 screw, not
a bolt. But if you put a little auto wax on the screw, she'll come
out if the goo oozed onto the threads. The screw doesn't have to
be real tight during cure, and a regular nut + toothed lockwasher,
not a self-locking nut, is preferred. After cure and removal of
the screw, install the tray.
Reg,
Fred F.
TaxSrv
> ...
> If the sidetone is missing, either the audio path is
> broken or the radio does not transmit properly. There
> is a slight possibility that the sidetone receiving circuit is
> the culprit, but it's so simple that the probability is tiny.
In the current Narco digital stuff, it isn't so simple at all. Can
be cantankerous.
> Assuming that the radio behaves in another plane,
I wish I were clear on this, as I thought it works for a while then
doesn't. If heat is causing that, then no assumption can be made
that the stack gets as hot in the other plane. The probable
circuit fault if such the case draws zip, so it doesn't heat up.
It would be other heat, from within and/or external to the box.
Reg,
Fred F.
nrp
It is a long shot but consider the possibility that spilled defroster
heat is cooking your radio stack. We had a Narco Com that went south
everytime after a few minutues in flight. We finally found it by using
a shop vac to blow air in the defroster duct & looked for an air leak
under the panel. Sure enough it blew air directly on the radio. Duct
tape etc fixed it.
RST Engineering
"Tauno Voipio" <tauno....@iki.fi.NOSPAM.invalid> wrote in message
news:Asz2f.359$cy3...@read3.inet.fi...
> The intercom and sidetone go different ways:
>
> - the intercom connects the amplified mic signal directly to the
> all the headphones,
>
> - the sidetone is created inside the COM radio by receiving
> the transmitted signal with a simple detector and feeding
> the signal to the headphone line.
That is not true. THe sidetone is generated by taking a sample of the
modulator's output. It is not an RF sniffer.
>
> If the sidetone is missing, either the audio path is broken or
> the radio does not transmit properly. There is a slight possibility
> that the sidetone receiving circuit is the culprit, but it's so
> simple that the probability is tiny.
>
> Assuming that the radio behaves in another plane, I see the
> possible causes:
>
> - the power supply to the radio is flaky,
Possible, but if the radio worked fine in another aircraft, it would have
been flaky there also.
> - the microphone signal path to the radio is flaky,
Would not explain loss of received signal.
> - the audio output path from the radio is flaky,
Most probable.
or
> - the antenna connection is broken / shorted.
Would not delete sidetone. I seem to recall in another post that a handheld
at a distance got carrier and not audio. If an antenna transmits, it
listens as well.
Jim