ACSS Transponder with ADS-B Failure

We had a failed ADS-B function of the left transponder system.

This was seen on the control head (bad image, but light indicates ADSB).



An ADS-B fault light was also present on the face of the transponder while performing a self test.



The problem was a failed GPS receiver in the cabin overhead.



This unit is manufactured by CMC Electronics . It provides highly accurate GPS positioning information to the transponders. The FMS's (Flight Management Systems) can also use positioning information from these receivers for GPS approaches and landings.

The internal troubleshooting ability of these modern electronics is amazing...atleast when it works the way its supposed to! And theres a reason there is redundancy built in! It appears there are 2 units ,is ADS-B a redundant system in all aspects?

Two of everything..... to ATC units each being fed data from it's own GPS receiver.