Hey guys I had an overhauled KT76 installed last February. Today, the transponder wasn’t lighting up and would only squawk 0400. I would rotate the dials to show my squawk code, but ATC would only get 0400. Any ideas? The light would work if I switched it to test mode.
KT76 transponder issues
- Thread starter Nick P
- Start date
Stewartb
Final Approach
It’s broken.
sourdough44
En-Route
There should be plenty on shelves collecting dust. Maybe buy a spare, swap it out?
If this happened between flights, make sure the unit is fully seated in its rack.
Ill remove it and hit the contacts with some contact cleaner and re seat it. Hopefully that solves the issue.
Capt. Geoffrey Thorpe
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Of course, once you remove it from the rack, to be in strict compliance with regulations, you need to get it checked by your avionics guy.
Just a reminder.
Not that anyone is going to check.
https://www.ecfr.gov/current/title-...x A to Part 43#p-Appendix-A-to-Part-43(c)(31)
Just a reminder.
Not that anyone is going to check.
https://www.ecfr.gov/current/title-...x A to Part 43#p-Appendix-A-to-Part-43(c)(31)
Except as noted above will technically require at a minimum a functional test which you probably cant perform. Just push on the unit and see if it reseats in the rack and your problem goes away. If the unit is tight and doesn't move then definitely have other issue.
Note well if we're talking a KT76 vs. 76A vs.78. The former has a different pinout than the latter two.
Its a KT76 not 76A. I saw the 78 and 76 are direct swaps?
I found a shop https://www.transponderrepair.com/ seems like it may be worth a shot to send my transponder to them before spending a lot more on a replacement
I don't think so. The 76A and the 78 are compatible.
FWIW: if you brought your aircraft to me to fix it, the 1st thing I would do is get a shop involved that could ramp check the system. With those results in hand you could then better determine which is the best route to take. Without any troubleshooting you may not find the result you are looking for. Regardless, any work performed on the xspndr system will require function checks or recertification, so you may be money ahead to get a local shop involved now.
Curious. Is there no warranty on this overhauled 76 you have now? Any reason why you don't want to inquire with the shop that installed it for this problem?
I bought the plane and it came with an overhauled transponder. I didn’t deal with the shop and the seller said the transponder had a 90 day warranty.
I found a shop that will overhaul it between $135-289 depending on parts. If it doesn’t make sense to overhaul due to cost they will charge a 75 service fee or you can give them the transponder for parts to avoid the fee.
Also, have a guy from the 150152 forum that will sell me a KT-78 for $150, but now I’m not sure if that will work with my tray
I’ll get everything tested by a shop near me to be covered
I found a shop that will overhaul it between $135-289 depending on parts. If it doesn’t make sense to overhaul due to cost they will charge a 75 service fee or you can give them the transponder for parts to avoid the fee.
Also, have a guy from the 150152 forum that will sell me a KT-78 for $150, but now I’m not sure if that will work with my tray
I’ll get everything tested by a shop near me to be covered
Last edited:
unsafervguy
En-Route
the best thing to do is throw that old POS in the trash and pony up for a new solid state transponder. those things were outdated 30 years ago. its just going to keep costing you money. they stopped making the cavity tubes in them years ago. as it has been stated, every time it comes out, it legally must be re-tested. sometimes spending a little more now pays off down the road.
@unsafervguy I usually agree and try to upgrade stuff when it breaks. However, I got a quote for $2500 to put a used Garmin GTX 327 in the panel (incld. labor). I'll spend $200 to get this old transponder fixed before I drop that kind of money
unsafervguy
En-Route
at 2500 your getting ripped off. those things go for less than 1 amu and only take a couple of hours at most to install. when my at-50 died and i replaced it with a garmin gtx-335 it took me a couple of hours to install including the GPS antenna.