Super Electromagnetic Machine Voltes V: Volume 10

Included:

S01E19 Cry at Your Father's Chest
October 8, 1977 TV Asahi
Zuuru held Gou in an island and tortured him to pry secrets of Voltes. Daijirou found a huge cave in the island and decided to investigate. He got caught and was thrown into a jail and met his father. When they tried to escape, Gou got caught again by Zuuru, but he managed to throw a piece of cloth with numbers written in blood to Daijirou.

S01E20 The Mystery of the Blood Numbers
October 15, 1977 TV Asahi
Voltes team tried to figure out what the numbers written on the cloth mean. The figure turned out to be a pulsating wave frequency. Dr. Gou transmitted this wave by using a mini transmitter and by tracking the wave, Voltes can trace his whereabouts. Meanwhile Zuuru created Zoru Geru, an amoeba-like robot that can heal itself or even change form. When he failed to defeat Voltes, Zuuru was tortured by Heinell as punishment.

Note: You know the drill, all names and titles are different in the English dubbed version.