television tube vs picture tube

television tube and picture tube both are nouns.

Word	Noun	Adjective	Verb	Adverb
television tube	Yes	No	No	No
picture tube	Yes	No	No	No

As nouns, television tube and picture tube are synonyms defined as:

television tube and picture tube: a cathode-ray tube in a television receiver; translates the received signal into a picture on a luminescent screen

Other synonyms of television tube include kinescope.

television tube (noun)	picture tube (noun)
a cathode-ray tube in a television receiver; translates the received signal into a picture on a luminescent screen	a cathode-ray tube in a television receiver; translates the received signal into a picture on a luminescent screen