HP 30b Mode Settings

[Joe Horn]

That's strange; those modes are supposed to persist. If they don't, I'd suspect it's either operator error (e.g. not changing the modes correctly) or a hardware problem (I'd guess either a low battery or a flaky connection somewhere, such as the battery contacts).

Let's rule out operator error: After pressing MODE, then pressing either arrow key 5 times to get to the RPN option, then pressing INPUT to rotate RPN into view, you should press the ON key to exit that menu and carve your RPN choice into stone. If you're doing that, and you still lose RPN mode, try changing the battery and/or cleaning the battery terminals.

Needless to say, resetting memory clears RPN mode. But I won't mention that, because it's needless to say.

EDIT: Oh! It just struck me! Do you have a program in memory which changes the modes? <Sorry, I should have thought of that first.>