I have the H/K avr210 and had a very hard time with it
as well. I did finally manage to get the codes you are
looking for(with a combination of other remotes and
hours of work)that work great for my avr210. I will try
to upload my ncf to this site. It may be worth a try to
see if it will work for your avr510. 'cause I know you
will have very few options, I looked for months!

My ncf also has some other very difficult learned
codes and discretes for this reciever and: Tv Toshiba 42H81, Sat/HD Reciever Toshiba Dst300, DVD Pan. rp56

Good Luck!!
Russ