In the early days of television, both the transmission and the television sets performed poorly. A broadcast frequently announced “Please do not adjust your receiver/set” to explain a transmission problem.
 
“Please do not adjust your receiver” has been cited in print since at least 1952 and “Please do not adjust your set” from 1954. A children’s television series from London (1967-69) was called Do Not Adjust Your Set. “Please do not adjust your set” quickly became a standard joke to explain any bizarre behavior on television.
 
 
Wikipedia: Do Not Adjust Your Set
Do Not Adjust Your Set (DNAYS) was a children’s television series produced originally by Rediffusion, London, then by the fledgling Thames Television for British commercial television channel ITV from 26 December 1967 to 14 May 1969.
 
The show took its name from the message (frequently seen on the TV screen in those days) which was displayed when there was a problem with transmission. Although originally conceived as a children’s programme, it quickly acquired a cult crossover following amongst many adults, including John Cleese and Graham Chapman (as mentioned by Cleese himself in the “Paying my ex wife” stage performance tour, October 2010).
     
29 September 1952, Oneonta (NY) Star, “About Town” by The Staff, pg. 4, col. 4:
Flash on screen: Please do NOT adjust your receiver.
 
15 February 1953, Canton (OH) Repository, “Magic Lantern” by Frank Tripp, pg. 16, col. 7:
Television Has Its Problems Too
Starting off at what once was movie time, after the evening paper has been read and the dishes washed, Mom moves in, plunks herself into her favorite chair and asks, “What’s on tonight”: You turn the knob on your new magic lantern.
 
The first scene is, “Don’t adjust your receiver.”
 
19 January 1954, Rockford (IL) Morning Star, “Robot Waiter A Cold Fellow” by Frank Tripp, pg. 4A, col. 3:
Don’t adjust your receiver. You have listened to a true story. Names and addresses have been omitted to protect the innocent. Be with us again next week; same time, same papyrus.
 
22 October 1954, Winnipeg (Manitoba) Free Press, “There’s No One Who’s Anti-DURANTE; Jimmy’s TV Program May Come To Winnipeg,” pg. 10, col. 1:
IF you should happen to be watching TV this fall and suddenly an odd-shaped phenomenon comes weaving across the screen, please do not adjust your set.
 
Google News Archive
27 June 1958, Montreal (Quebec) Gazette, editorial cartoon by John Collins, pg. 8, vol. 3:
Do Not Adjust Your Set
 
Google News Archive
4 September 1960, St. Petersburg (FL) Evening Independent, TV Week Magazine, pg. 6, col. 1:
Please do not adjust your set
Here’s what is happening behind the scenes
   
10 June 1961, Rockford (IL) Register-Republic, “TV Tee-Hees” (comic), pg. A9, col. 7:
(A person is watching a black screen—ed.)
“This program takes place in total darkness…do not adjust your set!”
 
19 October 1962, Dallas (TX) Morning News, sec. 1, pg. 4:
This paragraph is deleted. Do not adjust your sets, the difficulty is at the point of origin.—WICK FOWLER.
 
OCLC WorldCat record
Do Not Adjust Your Mindset
Author: C Rajendra
Edition/Format:  Article
Publication: CONTOURS -BANGKOK- 7, no. 2, (1995): 25
Database: British Library Serials
 
OCLC WorldCat record
Do not adjust your set : the early days of live television
Author: Kate Dunn
Publisher: London : John Murray, 2003.
Edition/Format:  Book : English
 
OCLC WorldCat record
DO NOT ADJUST YOUR SET The whistling wilderness of old AM radio bands is set for a high-tech makeover
Publisher: [London : New Science Publications
Edition/Format:  Article : English
Publication: New scientist. no. 2512, (August 13, 2005): 44-47
Database: ArticleFirst