The blog of the special collections library at the Universade Complutense Madrid, "Folio Complutense" has an entry on their Hebrew Bible manuscript that served as the model for the Hebrew text in the Complutense Polyglot.
See here. Follow the link from the blog-post to a fully digitized version of the manuscript. Many other manuscripts in the collection, including Hebrew ones, have also been digitized.
Thanks to Marta Torres, head of Special Collections in the Complutense library, for alerting me to this.