Need more data to solve the problem. What does (all immediately after starting the engine) how do they change with time and revs. Does cycling the alternator side of the master switch make any difference to the lights. The alternator warning light normally means the alternator is of line as with the alternator switched off. When you say a positive charge, how many amps. There should be a large charge that reduces as the battery recovers from engine start. The avionics should be off at engine start. Even starting with the alternator off is a good idea reduces load on battery. Would not expect alternator warning light on and a positive charge or the diode pack to be bad.
So a bit more info would help.