the depth-charge throwers were removed in 1936 and more 200-kilogram depth charges were carried in their place. the navy reconsidered its anti-submarine warfare tactics after the war began in september and intended to reinstate the depth-charge throwers, although these were an older model than the one previously installed; "tartu" had not received her as of early 1942. as an interim measure, a pair of rails were installed on the stern for depth charges. each rail could accommodate three depth charges and ten more were stored in the magazine. during the ship's mid-1941 anti-aircraft refit, the mainmast was replaced by a platform for a single 37-millimeter twin-gun mount and two of her single 37-millimeter mounts were transferred to the platform while the other two single mounts were removed. the hotchkiss machineguns were on new platforms between the funnels and a pair of browning 13.2-millimeter aa machineguns were installed in front of the bridge. "tartu" received a british alpha 128 asdic system in october 1941 that had been taken from another ship.