Farnsworth Image Dissector

[oldradio99]

I recently came across this tube pictured and am having a challenge determining value. I am not a TV collector per se although I do one 1 Predicta, 1 mechanical TV and 1 little cute Emerson.

The only recorded sale seems to have been at the 2010 museum auction where one of these sold for $17,000. I have been told it was because two museums wenthead to head but I dont know which two or who won and lost.

I came here because my normal discussion boards had no information.

Can anyone assist a radio collector who knows little about TV's?

Thanks

Art

[rld-tv01]

I was at that auction from the Farnsworth museum in Indiana. The two high bidders were both internet bidders. One of them may have been the museum which was terminating the space for the Farnsworth museum due to lack of visitors. Since the Capehart Fansworth plant was located in the same area the museum wanted to obtain a few locally maufactured items for a more general manufacturing exhibit versus tv museum. For some reason the museum did not want to bid on site at their own museum. I not sure if they won the image disecror or not. Also the image disector was advertised as late 1920s which meant it may have preceded the RCA zworykin Iconoscope. There was some speculation it was not that old. Farnsworth bother-in-law hand blew the glass for the earliest Image disctors. Image Discectors were usedc to monitor heat from furnaces in the 1930s. The ETF museum has a Image Discetor and camera from one. There were 4-5 other Image discetor at the auction. I got a cracked one for about $100. If yours can be dated etc then it would help determine the value. As shown I would put it in the $400 range since that is what Iconoscopes go for on eBay. I would contact Steve at ETF since he has 3-4 Image Discectors.

[oldradio99]

Originally Posted by rld-tv01

I was at that auction from the Farnsworth museum in Indiana. The two high bidders were both internet bidders. One of them may have been the museum which was terminating the space for the Farnsworth museum due to lack of visitors. Since the Capehart Fansworth plant was located in the same area the museum wanted to obtain a few locally maufactured items for a more general manufacturing exhibit versus tv museum. For some reason the museum did not want to bid on site at their own museum. I not sure if they won the image disecror or not. Also the image disector was advertised as late 1920s which meant it may have preceded the RCA zworykin Iconoscope. There was some speculation it was not that old. Farnsworth bother-in-law hand blew the glass for the earliest Image disctors. Image Discectors were usedc to monitor heat from furnaces in the 1930s. The ETF museum has a Image Discetor and camera from one. There were 4-5 other Image discetor at the auction. I got a cracked one for about $100. If yours can be dated etc then it would help determine the value. As shown I would put it in the $400 range since that is what Iconoscopes go for on eBay. I would contact Steve at ETF since he has 3-4 Image Discectors.

Steve did give me a number. Not sure how to date this one as the only markings are numbers letters and numbers scratched on the inside - DAOSI 82. This one has a paper tag clearly marked Farnsworth experimental so that helps. Would love to know who the interest buyers were and who was the loser.

[rld-tv01]

I would think yours is a 1930s or early 1940s? The cracked one I purchased was somewhat smaller then the ones Steve has on display in his ETF museum. Look at the two image dissectors at http://aade.com/tubepedia/1collection/tubepedia.htm Yours looks similar to the image of his friends tube. Maybe my $400 estimate was a little low? There are a lot of WW-II sniper image dissectors advertized from time to time on eBay. I have picked up three of them over the years. They go from $10 - $150. A lot don't sell at $40. They are only about 5 inches long and an inch and a half in diameter. So I believe if you look at pictures on web sites discussing the properties of the images disectors you can find ones which match yours. I believe Farnsworth was always trying to improve the image dissector so the newer ones had features you won't find on the older ones. A 1933 patent of Farnsworth image dissector http://patentimages.storage.googleap...S2087683-0.png

[rld-tv01]

I took this picture last year at the ETF convention of two image dissectors on display at the museum. The top image dissector looks similar to yours. The ETF museum labeled this one as from the 1940s.

[zenith2134]

Can anyone elaborate on the theory of function for an image dissector? How does it differ from a vidicon/plumbicon type sensor? From what I understand, they use a different phosphor type and perhaps the scanning is by alternate means? The diagram I've seen appear to use some sort of plate electrodes. Never learned about this type of photo tube.

[bandersen]

There's a fun little documentary on YouTube narrated by Jessica Farnsworth - his great granddaughter. It shows the basic theory behind the dissector.

http://youtu.be/HHy04aN0jfI

[peter scott]

Originally Posted by zenith2134

Can anyone elaborate on the theory of function for an image dissector? How does it differ from a vidicon/plumbicon type sensor?

The essential difference between the image dissector and the iconoscope and all more modern designs is that the image dissector signal output is only generated for the instant that the light was hitting the target coincident with the scanning beam. In other words a very brief instant.

In the iconoscope the signal output is the accumulation of photo electric charge from light acting on the target for the full duration of one frame.

This is why Farnsworth's tube was so insensitive relative to the iconoscope.

One attempt to improve it's sensitivity is shown in the tube under discussion here in that it has an electron multipler attached to the target. (The reason for all the connection pins.)

Peter

[oldradio99]

Originally Posted by rld-tv01

I took this picture last year at the ETF convention of two image dissectors on display at the museum. The top image dissector looks similar to yours. The ETF museum labeled this one as from the 1940s.

I believe you are right. The top tube looks exactly like the one I have.

As soon as I can I will post the dimensions.

[oldradio99]

Not sure if it means anything to dating this tube but the diameter is 4 1/2 inches and the length of the large section is 7 1/2 inches.

[rld-tv01]

The Farnsworth Television and Radio Corporation was founded in 1938 according to http://en.wikipedia.org/wiki/Philo_Farnsworth "In 1938, Farnsworth established the Farnsworth Television and Radio Corporation in Fort Wayne, Indiana, with E. A. Nicholas as president and himself as director of research." Also the same Wikipedia web-page states "Farnsworth Television and Radio Corporation was purchased by International Telephone and Telegraph (ITT) in 1951." There is an 1943 magazine advertisement for a similar Image Discector http://www.earlytelevision.org/image...ector_1943.jpg So I would think early 1940s on your tube would be a close date? You can download the Farnsworth book that Wikipedia cites as reference at http://www.earlytelevision.org/pdf/s...00everrich.pdf

[oldradio99]

Originally Posted by rld-tv01

The Farnsworth Television and Radio Corporation was founded in 1938 according to http://en.wikipedia.org/wiki/Philo_Farnsworth "In 1938, Farnsworth established the Farnsworth Television and Radio Corporation in Fort Wayne, Indiana, with E. A. Nicholas as president and himself as director of research." Also the same Wikipedia web-page states "Farnsworth Television and Radio Corporation was purchased by International Telephone and Telegraph (ITT) in 1951." There is an 1943 magazine advertisement for a similar Image Discector http://www.earlytelevision.org/image...ector_1943.jpg So I would think early 1940s on your tube would be a close date? You can download the Farnsworth book that Wikipedia cites as reference at http://www.earlytelevision.org/pdf/s...00everrich.pdf

I think I agree so doubt that this is the $17,000 version.

If I wanted to sell, and I am not sure yet, where would the best place to sell? I have no idea and I am not sure that EBay is the best place to attract the real collectors.

Would love some opinions.

Thanks

[rld-tv01]

The ETF classified adds are free so couldn't hurt. Not sure which category, prewar, broadcast or parts? http://www.earlytelevision.org/classified_page.html

[Steve McVoy]

The likely buyer is a tube collector. Those guys watch Ebay, so I think it is your best bet.

[oldradio99]

For now decided to put into my display case. No rush to sell and if someone finds this thread and makes an offer I will deal with it. Thanks to everyone for their input and information.

Art