First of All Greeting from the UK Could some one please explain what is going on with the following: I have built and run several Dcc++ systems and JMRI using the Arduino Uno with no issues and all seems to work fine. I used an Arduino Clone and a Deek-Robot Motor shield 15v 2A power supply, again everything works. I appear to have sorted out my 308 error problems with this setup and seem to get good and consistant programming so I was keen to see if I could add wi-fi etc. I decided to experiment and build one with an Arduino Mega using either the Dcc++ ex software or the original Dcc++. So following the original instructions I used the same Deek-Robot Motor shield and Mega 2560 (Clone) and using one jumper from Pin4 to Pin 13, i loaded up the original basestation Dcc++ software. Before attempting to program anything I decided to test the voltage on the Main Track and Program Track Outputs: Main Track 15v (ac) Program Track 30v (ac) or 14v(dc). Using a multimeter on the ac setting gets 15v on the Main Track.On the Program Track either 0 or 30v depending which probe goes to which terminal or on the dc setting 14-15v dc. They should both be 15v ac. I notice that only 3 of 4 leds light on the Motor shield, both are lit on ther Main, Only one is lit on the Prog side. The result is the same on 3 different Mega from 2 separate sources, purchased at least 12 months apart and 3 different Motor shields and I have checked all of my measuring equipment and downloaded the source code and tried that, same result. If I then remove the jumper from Pin4 to Pin 13 and load the Dcc++ ex software and repeat the measurements i get: Main Track 15v (ac) Program Track 15v (ac) which is what I expect.It works but I am struggling to get consistant programming with the 308 error back again. I have tried the suggested fixes on the dcc++ex threads but none seem to work. Does anyone have any idea what I am doing wrong here? It should be simple since it works ok with the Uno but I am at a loss to know what I have done?Probably something dumb! Any comments would be gratefully received.