No GPS if laptop is charging. strange

[sailouterbanks]

Strange issue with new setup. I've been using opencpn for several years with a usb GPS puck on my laptop. I just installed a standard Horizon GX2200 with GPS and AIS. I set up a serial to USB cable to input the gps and AIS signal to the laptop. I did a temporary setup and it worked great. After I ran the permanent wiring i couldn't get any GPS on opencpn. After several hours of checking all connections, i pluged my old puck GPS in and it didn't work either. I decided to give up for the day and try a different laptop later. When I unplugged my 12 V laptop power supply, the GPS indicator on opencpn immediately lite up! Plug it back in and it stops.

So running on battery I get GPS and AIS working. Hook up the charger and signal is lost. NEMA debug window is blank when plugged in. Any Ideas?

Richard Hess
S/V Island Thyme
OBX, NC