Almost All Digital Electronics TUBEPEDIA


Overall view of tube	Business end

View of Accelerating Ring Assembly	Socket

Left: Accelerating Ring Assembly Center: Tube assembly Right: Multiplier section	Internal Construction of an image dissector

The Image Dissector

The image dissector is a camera tube occasionally employed in industrial television systems. It is relatively insensitive, but it is useful where a scene is brilliantly illuminated.

To understand the operation of this tube, refer to internal construction diagram above. The photocathode is similar to that of the image orthicon; it emits electrons where light falls upon it. The combination of the focus coil and the focusing electrodes (accelerating rings) causes these electrons to move away from the cathode
toward the opposite end of the tube. Thus an electron image extends through the space of the tube and is brought to focus in a plane which passes through the aperture. At a given instant electrons from a single small point in the image pass through the aperture to an electron multiplier similar in principle to that of the image orthicon. The first dynode is directly behind the aperture. Eleven dynodes are usual.

Scanning currents, very much like those of other cameras, pass through the external deflection coils. In this case the entire electron image is deflected, rather than a narrow beam of electrons. The portion of the image which is deflected into the aperture produces the video at a given instant.

Electrons emitted from the remaining portion of the tube are wasted, rather than stored on the target as in the image orthicon. The image dissector has no storage characteristic which acounts in part for its low sensitivity. The image dissector is useful only where scene illumination exceeds 200 foot-lamberts. A popular application is viewing the interior of a furnace

The image dissector was invented by Philo Farnsworth in 1927.
My image dissector is a more modern version of his basic invention.


The F4012 is a 1" diameter tube designed to use standard Vidicon deflection and focus coils.	It is used whenever high-resolution, variable scan rate, high dynamic range, and reliable operation (does not have a filiment to burn out).	Closeup of the photomultiplier section.

Typical usage as slide-projector readers, hard-copy readers, electronically scanned spectrometers, and electronic star trackers.

Sold for amateur and experimental use.
(click images to view enlargement)

One unusual thing about the 1847 is that there is no direct connection between the mosaic and it's external signal connection.
Instead there is a ring of conductive material inside the tube, connected to the mosaic, and a ring of conductive material outside the tube with a signal connection. Thus the signal is picked up through this "capacitor" consisting of two plates, internal and external, with the glass as a dielectric.

A camera using the 1847 was described in the amateur radio magazine QST in May of 1940

RCA 1850 Image Iconoscope Camera Tube.
One of the earliest commercially available camera tubes.
circa 1950 (The earlier version, RCA 1850, dates back to 1939)
Selling price in 1948 was $540.00

Later Versions, the 1850A were painted supposedly to reduce stray light from getting in.

This image of Dr. Zworykin, made in 1933, is one of the earlist iconoscope television images.

A similar tube, the 1846, was used in a television guided bomb during the latter part of WW2.
The 1848 can be positively identifed by an extra CAP not on the 1846 as shown above.


The GB-4 Guided Bomb	GB-4 being dropped from a B-17

RCA Engineer showing 1846 iconoscope camera used in bomb.	Army officer piloting GB-4 to it's target

Insides of the camera. 1846 (outlined in red) can be seen at left with deflection yoke and lens.	Front view of camera with sketch of 1846 iconoscope tube it used.

Produced primarily as a low cost camera tube for Amateur and Experimental uses.

The circuit for the 1698 monoscope below could be used with the 5527 with minor modifications as the minimum complexity schematic.

The 5527 has 1/5 the output level and an additional video amplifier stage may be required.

This tube was used to produce printing on television images. (The antique version of a character generator ROM used in computers). It contains a metal mask with characters etched through. The electron beam scans the mask. Where the mask has been etched with characters, the beam passes through to a collector plate. The electron current from the collector plate is a video signal of the character.

CK1414F10C Character generator monoscope

It has an electrostatic deflection electron gun but in place of a screen it has a metal plate with engraved letters and numbers
connected to a pin on the front of the tube. The beam is made to scan the characters on the plate in the same way that
a character generator ROM is scanned to display text. Of course this is analog instead of digital but same function.: I'm told the CK1414 is based on a 3JP1 pinout and has 3WP1 gun characteristics.


Side View	Business End