A scale should be A B C# D E F# G# A. (The "G" needs to be a half step below the last A.)

By "I play the viola as a fiddle" do you mean that you tune the strings G D A E and not like a "normal" viola C G D A?

You could start with an open A string, and proceed up on that string, but with normal viola strings and tuning there isn't an E string.

If your strings are "tuned like a fiddle" then the A scale fingering is exactly like the D scale except you shift up "one string," starting with the open A instead of with the open D.

John