mathcal letters

[Angela Partain]

Hello! 
I have a question about using mathcal letters.  In all the years I've been using tex, I've never been able to get it to work properly.  I was able to fix the problem, but now I have a situation that's not working.

When I use {\cal A}, \cal{A}, {\mathcal A}, or \mathcal{A}, I get an A in Courier type. 

My fix has always been to put this command in the preamble:   \font\mcal=MTMS
and then type  \text{\mcal A} (in math) or just {\mcal A} in the text. 

This works fine unless the mcal letter needs to be sub- or superscript.  In that case, it appears the same size as a normal letter, rather than superscript size.   I tried this:
\text{\scriptsize {\mcal A}}, to no avail.  

Any suggestions for me?  Thanks so much for your assistance!
Best regards,
Angela