7JP4
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The 7JP4 is an early American television picture tube that was installed in the late 1940s. The screen diameter is 18 cm and the luminous color of the screen is white. Under the designation 7JP1 , an identical tube with a green luminous shade was available, which was primarily used in measuring devices. In contrast to conventional television picture tubes with magnetic deflection , the electron beam is deflected electrostatically . The 7JP4 is actually closer to the oscilloscope picture tubes than the TV picture tubes.
A voltage between 600 and 900 volts is required for the electrostatic deflection; almost no current flows. The anode voltage is 6 kV. The deflection angle is limited to max. 40 ° which is reflected in a correspondingly long tube of almost 40 cm. Picture tubes with magnetic deflection work with deflection angles of 70 °, 90 ° and 110 ° and are therefore much shorter. A television with a 7JP4 gets by with only 100 W due to the low deflection power, while televisions with magnetic deflection in this era achieved up to 300 W.
Although the screen diameter was relatively small at just under 18 cm and many television viewers even used magnifying glasses filled with water , the comparatively inexpensive 7JP4 enabled television in the USA to make its breakthrough as a mass medium in the 1940s . For example, televisions with the 7JP4 could be sold for under $ 200 , and sets with a screen diagonal of just under 8 cm were available for under $ 100. The average monthly wage during this period was around $ 150.
The 7JP4 was used in the following device models, among others:
- Motorola VT-71, VT-73
- Hallicrafters 505
- Sentinel TV-400, TV-405
- National TV-7W
- Philco 50-T701, 50-T702
- Tele-Tone TV-149
Individual evidence
- ↑ 7JP4 data sheet ( Memento from October 6, 2007 in the Internet Archive ) (English; PDF; 168 kB)