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Mark 12D Problem???



 
 
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  #11  
Old July 8th 05, 06:15 PM
three-eight-hotel
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Arrgghhhhhh!!! :-(

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

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  #12  
Old July 8th 05, 07:28 PM
Ross Richardson
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I recently had a problem at not transmitting; no sidetone. however I was
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 wrote:
Arrgghhhhhh!!! :-(

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

  #13  
Old July 8th 05, 07:50 PM
three-eight-hotel
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yeah... I keep thinking (man, if I just had 10 or 15k laying around,
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

  #14  
Old July 8th 05, 08:27 PM
Ross Richardson
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One of the trouble shooting things I did what to swap radios in the two
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 wrote:
yeah... I keep thinking (man, if I just had 10 or 15k laying around,
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

  #15  
Old July 9th 05, 12:03 AM
three-eight-hotel
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Well... My old instructor just took a student up in a 150, with my
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

  #16  
Old July 9th 05, 04:05 AM
Clyde
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Don't waste your time on Narco junk, it will save you time, headache and
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" wrote in message
oups.com...
I have been struggling with a radio problem for some time now and am
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!



  #17  
Old July 11th 05, 03:33 PM
three-eight-hotel
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Okay, so it's not the radio..... ??? I took off with the TKM,
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!

  #18  
Old July 11th 05, 05:01 PM
RST Engineering
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Think about it, grasshopper. The receive circuits ("scratchy reception")
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" wrote in message
oups.com...
Okay, so it's not the radio..... ??? I took off with the TKM,
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???



  #19  
Old July 11th 05, 05:30 PM
three-eight-hotel
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Okay, so bear with me cuz technical electronics is not my forte'. I
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!!!

  #20  
Old July 11th 05, 06:00 PM
nrp
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I know it's summer, but I once found a leaky defroster hose spraying
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.

 




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