I have a C2200 and have changed tubes many times - finally settling on NOS Amperex - a tremendous improvement over the stock Chinese tubes.
In addition to the screws on the sides there are two on the back. After all are removed you do have to carefully pry it backwards (and upwards ad Bigjoe suggests); there are no other (hidden) screws. After the top has been removed the first time, it comes off easily in subsequent removals.
In addition to the screws on the sides there are two on the back. After all are removed you do have to carefully pry it backwards (and upwards ad Bigjoe suggests); there are no other (hidden) screws. After the top has been removed the first time, it comes off easily in subsequent removals.