Wrong reported altitude

[mlallier]

Set-up: Dynon D-180 and KT-76 with dynon converter.

Last year this set-up was tested succesfully with ATC at 5500 ft.

Yesterday, went out at 7500 ft and controller told reported altitude was 14100, almost double!

Have an idea what is wrong? , the only thing I could think of:
I made a software update in between, ... or a connection becoming loose in the wiring?

Thanks,

 

[Brantel]

Most likely one of your Grey Code wires has a bad connection to the KT76.

You can try pulling the xponder and cleaning the contact surfaces of that edge card that mates with the connector in the back of the tray.

 

[mlallier]

Thanks for the input Brantel, will clean the contacts and check wires.

 

[dynonsupport]

Indeed, even a single bad encoder wire connection can cause the altitude to be off by a signifigant amount because of the encoding scheme used in gray code.