Hi John and welcome to the club. Some recent successful suggestions discussed are to thoroughly excecise all switches and potentiometers. Re-seat any internal cabling, tubes, etc...
Here is the FAQ section dedicated to the F-2B:
I'm sure others that have actual experience with the unit will chime in as well. I hope that this helps. Good luck with the solution and if necessary give Alembic a call and they will gladly assist.
Art