If the fuse has metal end caps then they often have the rating stamped (impressed) on one of the metal ends - you may need a strong light and a magnifier to see it.
The user manual is here...
http://filedepot.onkyousa.com/Files/own_manuals/tx_sv515pro.pdf?CFID=2543759&CFTOKEN=25454870&jsessionid=f0304863a119c1fa5925375a3e483d2171a4
Under PRECAUTIONS on page 2 it says...
AC Fuse - The fuse is located inside the chassis and is not user serviceable. etc etc
Which is a bit naughty of them...
Good luck...
Peccavi, May 2013
