Today I tried different airport since the others where payware.  I set NAV 1 and got a reading on one VOR 36 miles out and I had Autopilot function along with GPS was working, but once I took-off and into 1 minute of flight, all nav turned-off including GPS.  I started all over again, started the 727-200 and everything was working again, but this time I just sat there with engines running and with in 3 minutes all nav turned off again.

 What is causing this?