I solved the problem.
On the other decoder I did "opkg info samba-base" to see the package files and copied them from the working decoder to the other.
Afterwards I had to add some others missings links and files with evocative names and finally it worked!
Isn't perfect because the decoder menu said that Samba is not installed but the shares exist and work fines.
Indeed there was perhaps simpler because by doing "opkg info samba-base", you can see the line source: http://samba.org/samba/ftp/stable/samba-3.6.25. tar.gz
This link and file still exists, I download it . The problem is that it contains a lot of things for many systems and I don't know how to transform it into ipk or how to use it for install.
Thanks to master G who suggested the way to me