7jp4
Encyclopedia
The 7JP4 is an early black and white cathode ray tube
used in late 1940s televisions. It has a 7" diameter round screen which was often partially masked. Unlike later electromagnet
ically deflected TV tubes, the 7JP4 is electrostatically deflected like an oscilloscope tube.
Because it is electrostatically deflected and was obsolete by the mid 1950s, most CRT testers will not test the 7JP4 and thus it is best tested in a working TV set. One notable exception is the Jackson 707 Cathode Ray Tube Analyzer which is capable of testing the 7JP4 along with the 3KP4 and other electrostatically deflected CRTs.
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Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
used in late 1940s televisions. It has a 7" diameter round screen which was often partially masked. Unlike later electromagnet
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...
ically deflected TV tubes, the 7JP4 is electrostatically deflected like an oscilloscope tube.
Because it is electrostatically deflected and was obsolete by the mid 1950s, most CRT testers will not test the 7JP4 and thus it is best tested in a working TV set. One notable exception is the Jackson 707 Cathode Ray Tube Analyzer which is capable of testing the 7JP4 along with the 3KP4 and other electrostatically deflected CRTs.
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| The 7JP4 was used in the following sets (incomplete list): |
|---|
| Motorola VT-71 |
| Motorola VT-73 |
| Hallicrafters 505 |
| Sentinel TV-400 |
| Sentinel TV-405 |
| National TV-7W |
| Philco 50-T701 & 50-T702 |
| Tele-Tone TV-149 |