Mark 12D Problem???
three-eight-hotel
having a tough time finding the real "root cause"! (I have a Narco -
Mark 12D)
It started several months back, when I would occaisionally get a "stuck
mike". After several phases of trouble-shooting, it appeared to be a
problem with the audio panel, which was replaced and seemed to solve
the problem.
A month or so ago, I lost contact with ATC while shooting some practice
approaches... Apparently, they could hear me, but I couldn't hear them
(confirmed by using my hand-held). Ever since then, I have been having
strange issues with the radio, but it will occaisionally work fine for
20 minutes or so???
Symptoms:
1. No side-tone when transmitting???
2. Occaisional loss of reception on known frequencies
3. No response (on known frequencies) to transmissions
I took the radio into a Narco dealer and they confirmed a problem with
the transmission switch (replaced a diode) and yellow-tagged the radio.
I put the radio in the plane and it worked like a champ for about 30
minutes and started to exhibit the symptoms again??? I took it back to
the dealer and the bench tested it for a couple of hours and said that
it worked fine and everything was within specs! :-(
I'm worried about throwing good money after bad and don't even know
where to begin in resolving this issue. (I can't afford to throw a lot
of money at new avionics and would like to get what I have working, if
at all possible)
Does anybody have any recommendations at troubleshooting this problem?
My mechanic is at a loss as well. The loss of side-tone, while
transmitting, seems to be an interesting issue...
Any suggestions would be greatly appreciated!
Roy Page
problems by changing of audio panel.
Various radio shops never found a specific fault.
What audio panel do you have ?
Roy
"three-eight-hotel" <todd_p...@dstoutput.com> wrote in message
news:1120577488.4...@o13g2000cwo.googlegroups.com...
RST Engineering
fine for half an hour, then crapped out again". You repositioned the
connector and it worked it's way back by vibration to it's normal
intermittent position.
Eliminate problems one by one. Does your audio panel have a bypass mode or
can you patch-pin around it to hardwire the radio into the aircraft system
and eliminate all the other radios? What other avionics are sharing the
audio panel wiring? Can you shut everything down except this ONE radio to
see if it really is the radio?
As to the Narco dealer replacing an intermittent diode ... hmmm ... never
yet found an "intermittent" diode in the last 50 years of designing and
fixing this stuff. The diode is good or it isn't. There isn't any
in-between. Intermittent solder connections ... thousands. Intermittent
semiconductor parts ... for all intents and purposes never.
Jim
"three-eight-hotel" <todd_p...@dstoutput.com> wrote in message
news:1120577488.4...@o13g2000cwo.googlegroups.com...
three-eight-hotel
Yeah... My mechanic and I both questioned the repair, especially at a
$430 cost!!! :-( The yellow-tag should offer some peace-of-mind, that
at least the radio is airworthy though, shouldn't it???
The audio panel is a (I'm showing my ignorance now) standard Cessna
(ARC???) panel, with marker beacon, like the one shown here:
http://williams.best.vwh.net/172RG_POH/7-40.html#AUDIO%20CONTROL
I've got a four-place intercom, that I was beginning to question, but
to be honest... I don't know what the heck I'm doing! ;-) I want to
jump in and start figuring this out, but I'm afraid of messing things
up. My mechanic is really cool and is working well with me to try and
figure this out, but I think he is over his head a little when it comes
to avionics.
I would like to figure out if I can route the radio directly to the
aircraft system, like you mentioned... I tried using the aircraft mike
and setting the audio panel to speaker, but it's so loud and difficult
to tell what's going on. I tried plugging my headset into the aircraft
plugs under the panel (not the intercom ones) and couldn't get that
figured out either. If I can get radio directly to those ports, I
could isolate the rest of the system... Any suggestions on how to go
about that? Based on the audio panel, provided in the link, there's
likely no bypass... would you agree?
Thanks again to both for your responses! The aviation community
continues to impress me and the web sure helps foster that community!
Best Regards!
Todd
three-eight-hotel
I have:
1) a stand-alone Mark 122 NAV with glideslope (not part of the radio
system)
2) ADF (Inoperable - receives but indicator is off)
3) four place intercom (generic - nothing fancy)
4) standard mode-C transponder (also not part of the radio system)
Pretty basic... Love to throw in a GNS 4 or 5 -30, but that's a
pipe-dream for now... (Single income/two kids :-)
Thanks again!
RST Engineering
you aren't "into" technician level electronics. If I've mischaracterized
you, I'll go at it from another route.
First, get yourself a can of tuner/control cleaner (Radio Shack 64-4315).
Do NOT use generic WD-40 or other petroleum based cleaner. You don't want
to leave a greasy residue AND you don't want to cob up the high frequency
characteristics of the connector(s). Mark 12D ... let me recollect ...
there are three or four versions of connector used on the 12D. Most
probably, since you have some sort of Cessna audio panel you have the
12D/Cessna version with the square block "Winchester" style connector.
It doesn't really matter. Use a very small amount of the cleaner on both
the radio connector and the tray connector. While the cleaner is still wet,
insert, pull, reinsert, pull, reinsert the radio half a dozen times.
Report results.
BTW, what model audio panel and model intercom do you have?
Jim
"three-eight-hotel" <todd_p...@dstoutput.com> wrote in message
news:1120581818.9...@g44g2000cwa.googlegroups.com...
NOS...@easily.co.uk
<j...@rstengineering.com> wrote:
>A classic connector symptom. "I took it out, put it back in and it worked
>fine for half an hour, then crapped out again". You repositioned the
>connector and it worked it's way back by vibration to it's normal
>intermittent position.
>
>Eliminate problems one by one. Does your audio panel have a bypass mode or
>can you patch-pin around it to hardwire the radio into the aircraft system
>and eliminate all the other radios? What other avionics are sharing the
>audio panel wiring? Can you shut everything down except this ONE radio to
>see if it really is the radio?
>
>As to the Narco dealer replacing an intermittent diode ... hmmm ... never
>yet found an "intermittent" diode in the last 50 years of designing and
>fixing this stuff. The diode is good or it isn't. There isn't any
>in-between. Intermittent solder connections ... thousands. Intermittent
>semiconductor parts ... for all intents and purposes never.
>
>Jim
I would tend to agree, they sould either work or die, but...!
We have 2x Narco 12D+ and one had an intermittent transmitt audio (and
sidetone) loss. We decided to leave it until the next service and use
the other set. That too became intermittent a couple of times, but not
at the same time. Just before being sent away they both decided to
fail on me at the same time.
I understand it was a known problem and due to a zener diode. Both
sets were repaired and have been working for 6 months.
It's not likely to be temperature related as it was during the winter
in Scotland.
three-eight-hotel
I beleive you are probably on to something with the connection
diagnosis... Vibration would be a great explanation to the 30 minutes
of working, then failure. I thought heat might have had something to
do with it to, but sometimes it fails at first attempt of using it.
I will try your suggestion and report back... (It may be a day or two)
I will also report back on models of audio panel and intercom I have.
(The second image in the link I sent "Figure 7-11 Used with Three
Transmitters" looks exactly like my audio panel, if it helps) The
intercom doesn't have anything indicative of a model on it, so I'll
have to poke around.
Thanks again and I'll report back soon!
Todd
three-eight-hotel
I bought the tuner/control cleaner yesterday and stopped at the airport
on my way into work this morning and did as you suggested... I sprayed
cleaner on the radio connector and tray connector and slid it in and
out half a dozen times. I then locked the radio into place (It seems
as though I got a better lock this time than I have in the past, as the
locking mechanism didn't seem to fall into place as well in the past)
I made a local "radio check" call and got a quick response of loud and
clear!
I won't be able to get out and fly it until probably Friday morning,
but will post back with the results. I just wanted to send a quick
update and let you know that I've got a good feeling about this!
Thanks for your help!
BTW - I checked out your website... Very nice! Looks like a lot of
cool products! I live in Garden Valley, near the Georgetown airport so
we are practically neighbors...
Back soon with results from the test flight...
Best Regards,
Todd
RST Engineering
and welcome to the sororfraternity.
{;-)
Jim
three-eight-hotel
I took a 45 minute flight to Willows this morning, for breakfast...
The radio worked like a charm all the way there... I took off out of
Willows, and 5 minutes into the flight (while monitoring Oakland
Center), I noticed the reception was getting scratchy, then... No
transmit, no reception, no side-tone while attempting to transmit. I
tried applying pressure to the radio to make sure it was seated
properly and even tried wiggling it a bit while applying pressure,
but... nothing!
However, about 5 miles out from Cameron Park airport the radio worked
for about a minute and enabled me to make a down-wind call. Then...
the same thing, no transmit, no receive, no side-tone while
transmitting! :-(
I think I confirmed (once on the ground at Cameron Park) that I can
plug my headset into the plane jacks and by-pass the intercomm, so
that's what I will try next, as well as throwing in a TKM that my
mechanic says I can try...
It sure seems like a vibration or heat issue??? Once on the ground and
the plane shut-down and secured, I plugged the headsets back in to the
intercomm and the radio worked like a charm. That would confirm the
several hour bench check done by the avionics shop. Something is
happening in flight... Any thoughts?
I couldn't get anything off my intercomm to provide a make/model. I
had my friend take a digital pic of the panel, so I should be getting
that soon, if that will help???
Todd
Ross Richardson
putting out a carrier. I corrected all the obvious problems that have
been mentioned and there were a couple of the finger contacts in the
tray not correct. But, in the end I returned it to Narco. They found
several problems one of which would relate to my problem of no sidetone
and no transmission. I got it back in fine condition for that problem. I
did develop another problem that the audio will not always break squelch
even when the volume knob is pulled out. I can 'solve' the problem by
turning up the volume until I hear the background sound (the audio pops
back as normal) and then turn it down and push it back in. The audio may
work the rest of the flight. I was in the habit of every few minutes of
pulling out the volumn knob to be sure it is still working. I do not
want to miss an ATC call. I contacted Narco and they will fix it under
my repair warranty. Otherwise, both of my MK12Ds have been good. The
other radio is needing a new display and may be sent to them during the
next annual and when I am satisfied that this radio is working.
Oh, to have the money to redo everything with new.
Regards, Ross
C-172F 180HP
KSWI
three-eight-hotel
how I could make some nice improvements). I do like the MK12D
though... It's a nice looking radio and worked very well until this
bout of issues I've been recently having.
I just wish I could isolate the problem directly to the radio! I think
we are going to throw it in one more airplane and put that TKM in mine
and see what plays out...
Thanks for your response!
Best Regards,
Todd
Ross Richardson
trays. The problem I had followed the radio, so I knew it was a radio
problem.
Regards, Ross
C-172F 180HP
KSWI
three-eight-hotel
Narco in it and flew it for just over an hour... It didn't act up at
all...
Next test... A (known to be working) TKM has been put in my plane and
I will go out and give it a shot this weekend. I'll post the results
on Monday...
Best Regards,
Todd
Clyde
money. I had to spend just over $700.00 on repairs to one which was just
out of warrenty. Even after the repairs, it only lasted a little over a
year. This radio had less than a hundred hours on it, I gave it a proper
home in our local dump, just where it belongs.
Clyde Woempner
"three-eight-hotel" <todd_p...@dstoutput.com> wrote in message
news:1120577488.4...@o13g2000cwo.googlegroups.com...
three-eight-hotel
yesterday morning, and it failed within 20 minutes! Same symptoms!
Reception started to get scratchy, then no transmission with a loss of
side-tone...
I'm not sure if it makes sense to isolate the audio panel from the
radio, since we have confirmed that the radio works in another plane
and a working radio does not work in my plane???
Is the audio panel the logical culprit? I failed to mention earlier
that the audio panel had been replaced last year with a used one,
because I was encountering a "stuck-mike"... However, the radio worked
fine for several months as I finished up my IFR work and took my
check-ride in the plane.
I haven't spoken with my mechanic yet this morning, but I'm thinking
that he is leaning towards the audio panel as well... Any next step
suggestions? See if I can swap out the audio panel with a working one
too, I guess???
Thanks for the feedback!
Clyde - I have seen a lot of unhappy Narco owners in the newsgroups,
and probably wouldn't make it one of my top choices if I were to go
down the road of buying a new radio. At this point, I'm trying not to
throw good money after bad and am just trying to get up in the air
again without having to rely on my hand-held! ;-) If the day comes,
where I am faced with the purchase of a new radio, I will probably bite
the bullet and see how I can tweak the finances to put in something
like a Garmin GNS with built in com. As for a second radio, I'll have
to start hitting the research! Best Regards!
RST Engineering
and transmit circuits (no transmission & loss of sidetone) are completely
separated in the audio panel.
What is the ONLY element in the chain common to both transmit and receive?
Do the words antenna/feedline strike a familiar note?
Jim
"three-eight-hotel" <todd_p...@dstoutput.com> wrote in message
news:1121092424.6...@z14g2000cwz.googlegroups.com...
three-eight-hotel
can talk software and web development all day long, but circuit talk
hurts my head... ;-)
If I get scratchy to loss of reception, that's going through one
circuit path in the audio panel. No transmission and side-tone loss is
taking another route in the audio panel. So what I think you are
saying is that it is not likely that both circuits went bad at the same
time?
The antenna was just replaced with a brand new one and my old one is
currently on eBay to minimize my losses! That would leave the
feedline... Is that something I could easily replace on my own? Would
that be a legal thing for me to repair or should I just point my
mechanic in that direction and eat the cost of the feedline and
installation labor?
Sorry for being such a knuckle-head... I guess I should have paid more
attention in those electonics classes? I do remember something like
"Bad Boys Rape Our Young Girls But Violet Gives Willingly"??? ;-)
Greatly appreciate the input!!!
nrp
hot air on one of our radios making it intermittent. We used a shop
vac duct taped to the defroster air inlet under the cowl to diagnose
it.
I also agree that Narco stuff was marginal & that zener diodes and
other solid state stuff doesn't become intermittent except for thermal
issues.
RST Engineering
>
> If I get scratchy to loss of reception, that's going through one
> circuit path in the audio panel. No transmission and side-tone loss is
> taking another route in the audio panel. So what I think you are
> saying is that it is not likely that both circuits went bad at the same
> time?
That is correct. The odds of BOTH circuits failing at the same time comes
somewhere around the odds of winning an argument with an FAA inspector.
Receive audio comes in one pin, goes to an audio processor, and out to a
phones/speaker amplifier. That's one channel. Sidetone also goes through
that channel.
Microphone audio comes in one pin, mic key comes in another pin, both go
pretty much unimpeded (except for a little diode switching) back to the
transmitter.
BTW, how do you KNOW you aren't transmitting? Are you transmitting carrier
but no audio? Or no carrier at all?
Does this happen on the ground? It seems to take about a half hour for the
symptoms to appear. Does it happen with just the radios on and the engine
stopped? You need to keep the battery up to voltage while checking it
static, so get one of those little 5-10 amp battery chargers to keep the
bats batting while you do the test.
>
> The antenna was just replaced with a brand new one and my old one is
> currently on eBay to minimize my losses! That would leave the
> feedline... Is that something I could easily replace on my own? Would
> that be a legal thing for me to repair or should I just point my
> mechanic in that direction and eat the cost of the feedline and
> installation labor?
Always look at the LAST thing you did before a failure to localize the
problem. How do you KNOW the antenna is good? Can you get at the connector
at the base of the antenna to look at the possible corrosion and/or tarnish
of the silver plated body? And is the center pin pushed back into the body
of the connector? The tip of the gold plated center pin ought to be nearly
flush with the bottom plane of the connector. Me? I'd put a bidirectional
("Bird") wattmeter in the line and see what was happening when the transmit
failure mode happens.
Simply replacing the feedline is doing what is called "shotgun analysis".
That is, start replacing parts until it works right. That's lousy practice.
Besides, what makes you think a regular mechanic knows how to put an RF
connector onto coax? Most mechanics have less knowledge of electronics than
you do. Some are great. Others are machinists, engine gurus, sheetmetal
wizards, etc.. We all have our specialties.
As to the legality ... hmmm. Ron Natalie, do you know if the radio coax is
connected to the landing light circuit {;-) THe point being, what is
"easily" replaceable? Most aircraft run the coax along the instrument
panel, up the door post, across the headliner, through the aft bulkhead,
along the fuselage formers until it comes to the antenna. Other than
tearing the airplane completely apart, it is fairly simple to replace. Like
I said, go to all that work just to find that it isn't the problem? Not me.
>
> Sorry for being such a knuckle-head... I guess I should have paid more
> attention in those electonics classes? I do remember something like
> "Bad Boys Rape Our Young Girls But Violet Gives Willingly"??? ;-)
"Better Be Ready Or Your Great Big Venture Goes West".
Jim
Don Tuite
<j...@rstengineering.com> wrote:
> . . .THe point being, what is
>"easily" replaceable? Most aircraft run the coax along the instrument
>panel, up the door post, across the headliner, through the aft bulkhead,
>along the fuselage formers until it comes to the antenna. Other than
>tearing the airplane completely apart, it is fairly simple to replace. Like
>I said, go to all that work just to find that it isn't the problem? Not me.
Looking at the antenna connector is a good idea. But for shotgun
troubleshooting, I wouldn't be averse to temporarily running a length
of coax from the back of the panel through the cabin to the antenna
just to get a data point..
Don
RST Engineering
as antenna) I've sure got enough 50' cables that we could string one on a
temporary basis between radio and antenna just to eliminate that
possibility. While we are at it, we could patch in a Bird bidirectional
wattmeter and the fellow would at least know if he was putting juice into
the antenna. I'd be happy to lend him both, but NOT between now and
Oshkosh.
Jim
"Don Tuite" <don_...@MAILNOTSAUSAGEhotlinks.com> wrote in message
news:37f5d1d0p1atf580k...@4ax.com...
paquett...@gmail.com
I juste looks at the first letter of your email ,it about the Mark 12d first check if you have good electrical connection in your airplane , you can take another mark 12d an put. It instead of your if it work well into the other airplane an has some problem in yours then you know where to start . It's your airplane your your radio this is one way to solve part of it.
Robert