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The Iconoscope |
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| The
Iconoscope was the the first television camera tube to see widespread
use beginning in the late 1930s. It was the invention of Vladimir
Zworykin (1889-1982), a Russian immigrant who worked for RCA. Another site,
"TV History Through
Visual Images", features the work of Zworykin in great detail, with
many rare photographs, and is highly recommended. RCA manufactured several types of Iconoscopes (types 1846, 1847, 1848, 1849, 1850, 1850A, and 5527). All but the 1847 and 5527 had the unique barrel-shaped bulb with an angled neck. They came in two sizes. The 1846 and 1848 (introduced in 1940) were about 4 1/2 inches in diameter. The 1849 and 1850 (both introduced in 1939) and the 1850A (introduced in 1945) were about 6 1/2 inches in diameter. The odd shape was required because the electron beam which was used to "read" the video information from the photoconductive target needed to operate on the image side of the target. The 1947 (introduced in 1941) was a tapered tube which resembled a 2-inch cathode ray tube, such as the 902 or 2AP1, and was intended for amateur and experimental uses. The 5527 (introduced in 1947) had a 2 inch diameter tubular bulb and was intended for industrial and amateur uses. An alternate technology avoided the "same side" issue that led to the angled neck of the larger iconoscopes. The 1846, 1848, and 1850 were primarily used for live camera applications. The 1849 was used primarily for film-to-video applications. The 1846 was a military-specification unit used during WW-II for airborne television applications. The 1848 (introduced in 1940) was primarily used for portable camera applications. The 1849 and 1850 types were superseded in 1945 by the 1850A, which remained in production throughout the 1950s. Two examples of the 1850A are shown below. The first tube shown here is an RCA type 1849. It was used at W3XE, the Philco-owned experimental television station in Philadelphia. This became WPTZ in September, 1941 when the first commercial television broadcast licenses were issued. |
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| The camera lens focused the image on the target, as seen in this photo. This target, supported by a sheet of mica, was coated with an array of photosensitive dots (pixels). The electron beam was swept across the target, and the current flow from the target was proportional to the amount of light that was falling on each of the dots. |
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| A porcelain 6-pin base was used on the 1849 and 1850 tubes. The 1850A used a black Bakelite 6-pin base. The 1846 and 1848 types had an octal (8-pin) base with a metal shell. The 1847 had a Bakelite octal base. |
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| When I acquired this tube, it still had a foil wrapping in place which was apparently needed for electrostatic shielding when installed in a camera. Television was still very much an experimental medium in the late 30s and early 40s. |
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| This 1942 picture shows an iconoscope and amplifier chassis that were used in a developmental TV camera made by the American Television Corporation. The tube is, most likely, an 1850 iconoscope. Their engineers seem to have taken a different approach to shielding the tube (note the network of wires around the tube). |
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| This is an 1850A from the
early 1950s. This tube cost about $500 when new, which is roughly
equivalent to about $3500 in today's money. The neck of the 1850A
is about 2 1/2 inches shorter than that of the 1849 and 1950.
This tube appears to have been rebuilt at some time in its life. This procedure was commonly done with weak TV picture tubes, and involved cutting off part of the neck (containing the electron gun) and welding a new neck and gun in its place. The tube was then re-evacuated and sealed. The dark line around the neck just above the type number is where the new section was joined to the old tube. |
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| This is a later version of the 1850A. It was more heavily silvered on the inside, either for optical or electrical shielding. This tube was also used at WPTZ. |
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| The carton for the 1850A is a large affair, measuring about 14 inches square and 26 inches high. |