Transponder Issues

[Ksaunders]

Have a King KT 76C transponder that the tower told me on arrival Friday was sending out an "Intermittent" signal.  Upon departure later that evening, was told by control they were not receiving my transponder code when I hit "Ident" after takeoff.  I turned it off then on again and it seems it fixed the problem for the remainder of my IFR flight.  (Was handed off several times along my route and nobody else mentioned my transponder was sending an intermittent signal).

Question #1.  How do I have the transponder checked to make sure it is operating properly?

Question #2.  What shop does one recommend if the transponder needs to be removed for service?

Question #3.  I have a Master Switch and a Radio Master switch.  Radio Master is used for the on/off for all electronics.  I just don't feel right leaving the transponder "On" and turning all on/off with Radio Master Switch.  Should one use the transponder on/off switch and not leave in the "on" position?  Think this makes a difference on avionics?  

Any similiar experiences or advice is appreciated.  

 

[Jerry 5TJ]

Quote: Ksaunders

Have a King KT 76C transponder....

Question #1.  How do I have the transponder checked to make sure it is operating properly?

Question #2.  What shop does one recommend if the transponder needs to be removed for service?

Question #3.  I have a Master Switch and a Radio Master switch.  Radio Master is used for the on/off for all electronics.  I just don't feel right leaving the transponder "On" and turning all on/off with Radio Master Switch.  Should one use the transponder on/off switch and not leave in the "on" position?  Think this makes a difference on avionics? 

[Ksaunders]

Jerry, that is great information and much appreciated.  Thank you very much for your reply.  Be safe out there.  

[M016576]

Quote: Ksaunders

Have a King KT 76C transponder that the tower told me on arrival Friday was sending out an "Intermittent" signal.  Upon departure later that evening, was told by control they were not receiving my transponder code when I hit "Ident" after takeoff.  I turned it off then on again and it seems it fixed the problem for the remainder of my IFR flight.  (Was handed off several times along my route and nobody else mentioned my transponder was sending an intermittent signal).

Question #1.  How do I have the transponder checked to make sure it is operating properly?

Question #2.  What shop does one recommend if the transponder needs to be removed for service?

Question #3.  I have a Master Switch and a Radio Master switch.  Radio Master is used for the on/off for all electronics.  I just don't feel right leaving the transponder "On" and turning all on/off with Radio Master Switch.  Should one use the transponder on/off switch and not leave in the "on" position?  Think this makes a difference on avionics?  

Any similiar experiences or advice is appreciated.  

 

[OR75]

the tube in the kt-76a is the weakest part in an otherwise robust equipment. other than an electric contact issue, I can only think about the tube needing replacement. 

for those with a gns 430, 530 , a good way to check what the altitude the transponder / encoder is sending is to display the pressure altitude ( look at the manual to find on which page it is). but this would be more to troubleshoot the encoder.

[jnisley]

Several month ago our KT 76A started giving us problems, our avionics shop told us that that model is still worth repairing and recommended I have Bevan-Rabell from Wichita, Kansas take a look at it. The switchdeck was going bad so they replaced it with a used one that had a good photocell. They also replaced some other parts, ran hot/cold tests etc. total invoice was $525. I wouldn't want to spend much more than that on an older transponder but all things considered I'm happy.

[kerry]

Have you had it calibration check recently.  I was having the same issues and I let it go longer than 2 years.  My local avionics shop charged $150 for a VFR check and solved all my problems.  The sticker states removed transponder and aligned preselector and receiver local oscillator.

[jamesm]

Question #1.  How do I have the transponder checked to make sure it is operating properly?

            The method I use depends your surrounding airspace, but (Hopefully ATC isn't listening :-O)

             I will transition through a  class D aka ATA which has radar capabilities they will let you know if your                       altimeter is not in agreement  there altitude reading. I believe most  Altitude encoders use Grey code method  to transmit your altitude back down to the ground. What this means is should one of  the data lines becomes open or shorted your Altitude is going to magnitude off . So hypothetically speaking if you were to transition an airspace at say 2000 ft and your encoder has a shorted data line ATC would see something like 6800ft. So it like  having a form of error checking.  other wise how would really know what your Altitude is reporting.  To do a complete check out Altimeter / encoder system  you  would need  lot$ of  money for exp$ive test equipment which has to be calibrated frequently.

Question #2.  What shop does one recommend if the transponder needs to be removed for service?

I have use Avionics Unlimited in Texas So far really happy with there service but I waiting for the finial check once the plane gets back together. I heard great things about Avionics Unlimited from other Mooney people.

Question #3.  I have a Master Switch and a Radio Master switch.

Different points of view (POV) on this.   POV 1.) by adding or by having   avionics master switch there is a now a single point of failure in your  avionics bus circuit so should the avionics master fail so now all your avionics are INOP. Yes someone could add backup method to help alleviate this problem but you are more than likely going to add weight and complexities to the Avionics  circuit.

POV. 2.) you can turn on/off your avionics from switch. I am not sure why this good Idea but someone thought it was good. However  by doing this and leaving the avionics turned on you now have large on rush current which can be sometimes detrimental to the avionics. May be it looks cool by having one switch I don't know what the real reason is.

This is my 2 cents.

James

'67M20C

 

[jetdriven]

Quote: M016576

a shop that performs an "IFR cert" on your transponder should be able to test it for you, and you'll get the two year certification out of it as well.  They typically run about $200 bucks and include a test of your pitot/static system...  That will kill two birds with one stone (potentially)

[KSMooniac]

Bevan-Rabell in Wichita is a great shop.  I had an original KT-76 (not A, C, etc.) that rolled over a couple years ago and they gave a valiant attempt to repair it, but couldn't do so economically.  They have a lot of spares for parts harvesting, and the know-how to diagnose and repair as necessary for the least cost if it is repairable.

At the end of the day, mine was not salvageable and they gave me an old Cessna unit as a loaner until we could get a GTX-330ES in to replace it.  I'm happy with the choice... ADS-B ready, and TIS traffic displayed on my 530W.

I'd start with the easy stuff first...check your antenna and coax connections.  Usually the cable and connectors are the first culprit for intermittent operations.  If nothing is obviously wrong there, then proceed to a shop to test the unit itself.

[MARZ]

Mine had a bad solder joint on the antenna coax.