picture tube vs television tube

picture tube and television tube both are nouns.

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

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

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

Other synonyms of picture tube include kinescope.

picture tube (noun)	television 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