A very compact molecular beam epitaxy (MBE) source is presented. It contains three Knudsen-type crucibles, two resistively and one electron bombardment heated. An efficient water cooling is implemented to allow MBE deposition under ultrahigh-vacuum conditions. Due to its small size, the evaporator fits inside a DN 36 CF T-piece which makes a separate bakeout possible. Refills of the crucibles as well as changes of the source materials and even repairs of the source can be carried out within a few hours without breaking the vacuum of the main chamber. The design and the usage of the MBE source are described in detail and its functionality is demonstrated exemplarily with data of silver deposition on the silicon (111) surface.