Narco Mk12d Issue

hypnofonic

hypnofonic

Filing Flight Plan
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Jul 3, 2019
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20
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Sacramento, Calif.
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hypnofonic
Hello everyone, wonder if someone can help out with a radio issue im having with this (dreaded) mk12d. I realize I should just throw it away, but just trying to limp along until my other airplane is done..

Everything works as it should, fairly loud (could be a smidge louder), sidetone is great, rx and tx is great. Fly it for over an hour flight or so (more prevalent when its hot outside as well) and the volume will start to degrade and finally drop. It's like someone literally turns the volume down. Its barely audible (same through the airplane speaker as well), and if I pull the breaker or hit the PTT, it will get loud and then quickly drop volume back to barely low levels. Transmission during this is still good, as the tower can hear me, all output (including sidetone) is dropped. Seems internal to the radio as I tried another mk12d and did not experience the same issue (although the mic gain seemed so blown out, and VOR wasnt working, but the sound level was great throughout the flight).

Any idea or advice, besides I should just throw the damn thing away.. ? :)

Thanks!
Andy
 
Audio output transistor is overheating. My best guess. No idea who could fix it.
 
I am in Galveston for the week, but when I get back home, I will try to remember to look in my logs. I had a really good Radio guy that does Narco benchwork as long as he can get the parts. The output transistors should be an easy to get part.
 
I’ve had good experience with my old Narco’s, but that is strictly anecdotal. The Mark 12 D Glideslope as the backup in my Mooney serves me well. The old 120’s in the 140 work great, but the mechanical indicators will make them throwaways when they no longer work.

I actually have a backup 12D on the shelf that works fine except it takes fiddling to change frequencies. If you’re handy enough to take the freq switch out of yours and put in this one it could make a solid radio for a reasonable price.
 
Had our 12D repaired/upgraded to a 12D+ back in 2004, still going strong.
 
Installed a MK-12DR in the Sport in 96. Sent it back to Narco several times (so you know it was fixed a few years back), until they finally fixed it. I would loose audio after an hour or so. Shut it off for a few minutes turn back on and it would start to work again. Still works fine, just waiting for to bite the dust before I install something else. Don't quote me but as I recall they replaced a capacitor.

I still think I have the service paperwork, pm me if you want me to dig it out of me files..
 
I had nothing but bad experiences with a pair of 12D+'s. And this was back when Narco was still "claiming" to maintain them.
 
flyingron said:
I had nothing but bad experiences with a pair of 12D+'s. And this was back when Narco was still "claiming" to maintain them.
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I must admit I think I sent my 12D to them 3 times before they fixed it, PITA.. They did replace the display for free after it failed.
 
Knock on wood but mine is still going strong BUT each click of the knobs don’t guarantee a change in the number so it’s days are numbered as soon as Trig comes out with their new one
 
Timbeck2 said:
Knock on wood but mine is still going strong BUT each click of the knobs don’t guarantee a change in the number so it’s days are numbered as soon as Trig comes out with their new one
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I had the old MK-12 it had a pig tale with a 18 pin connector or so out the back of the tray. Does the Trig have a connector at the back of the tray?
 
AKBill said:
I had the old MK-12 it had a pig tale with a 18 pin connector or so out the back of the tray. Does the Trig have a connector at the back of the tray?
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Yes, but if you're asking if the Trig TX56/57 is plug and play, it isn't with the MK-12.
 
AKBill said:
You should introduce yourself. Location, what you fly .....:rolleyes:
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I have an early 1969 American Yankee AA1, and I am in Sacramento, California. First airplane for me, also slowly rebuilding a 1977 Grumman Cheetah, turning into a Tiger but it seems like its taking forever to get it flying!
 
AKBill said:
I must admit I think I sent my 12D to them 3 times before they fixed it, PITA.. They did replace the display for free after it failed.
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Oh, they fixed these things, the problem was two fold: they didn't stay fixed and that there was no loaner nor expeditred turnaround. When you're based at a class B primary airport, not having a radio is a AOG situation.
 
I fly out of a towered airport so not being able to hear is a giant pain!! I’ve used my hand held radio a few times. Currently its the only navcom in the airplane.
 
bradg33 said:
Bevan is one of the few shops that will still service Narco radios. Lots of parts, lots of knowledge. If you need a Narco fixed, they're the folks to talk to.
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Thanks for the info...:)
 
hypnofonic said:
I have an early 1969 American Yankee AA1, and I am in Sacramento, California. First airplane for me, also slowly rebuilding a 1977 Grumman Cheetah, turning into a Tiger but it seems like its taking forever to get it flying!
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I was looking at the AA1 but ended up with the Beech Sport. what does it take to turn the Cheetah into a Tiger? Engine?
 
Captain Ron has a Tiger-engined Cheetah.
 
AKBill said:
I was looking at the AA1 but ended up with the Beech Sport. what does it take to turn the Cheetah into a Tiger? Engine?
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Its funny, I was initially going to get a Musketeer but ended up with an AA1! :)

Basically, the only difference between the two is the engine (150hp vs 180hp) and a heavier duty spar. My cheetah had debonding issues (purple glue used by Grumman) in the wings (long long story) and I happened upon a crashed AG5B which had good wings and a good spar. I swapped the spar and wings and am waiting for an eventual 180hp swap.. for now the 160hp will do. It's been a long arduous process, but will be a nice airplane once its done!
 
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I had an AA1... with a Narco MK12D (as a backup.) Both the plane and the Narco worked very well for me...

I think you'll like the Cheetah!
 
Mk-12Ds are actually a more maintainable legacy radio then the KX-155. Very few of the internal parts are proprietary, and cross to stuff that is still available. The displays are available brand new for about $150, and the radio itself is pretty easy to work on. The service manual is also available online at several places (I got mine free).
 
Hello. All you guys that replaced or removed the old Narco radio, would any of you have a Narco tray your willing to sell? Thanks Frank
 
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