This TV was manufactured by the National Company, Inc. of Malden, MA in 1948.
National also made many very nicely designed radios, many of which are in the
museum’s collection. The TV-7 was available with a metal case, in the same style as
the National radios, for $189.50. Our example, in a mahogany wooden case, retailed
for $199.5. The TV-7 was also available in a very rare Videometer model that had a signal
strength meter replacing the left speaker. This TV is just new enough that it doesn’t
include TV channel 1.
This TV uses a 7JP4 7″ picture tube that was developed in the mid 1940s for RADAR
displays. The 7JP4 uses electrostatic deflection for the electron beam instead of the
more modern magnetic deflection. Electrostatic deflection requires high voltages in
the beam deflection circuits. The high voltage capacitors are expensive to replace
during restoration. Picture tube manufacturers developed a royalty-free magnetic
deflection circuit in the 1940s that allowed them to make much larger picture tubes
without needing very high deflection voltages. The P4 in the picture tube part number
means that it has a phosphor that glows white and has medium persistence. The
viewable TV picture was 4-3/16″ x 5-3/4″. There are plugs in the case above the picture tube that could be removed to mount an optional magnifier.
Cost in 1948: $199.50 (about $2,661.09 in 2025 value)
Vacuum Tube Count: 21
This TV was restored by the donor and is operational.
The vacuum tubes used in this TV are:
| Tube | Type | Function |
| V1 | 6AU6 | R.F. Amplifier |
| V2 | 6AG5 | Mixer |
| V3 | 6C4 | Local Oscillator |
| V4 | 6AU6 | First Video I.F. Amplifier |
| V5 | 6AU6 | Second Video I.F. Amplifier |
| V6 | 6AU6 | Third Video I.F. Amplifier |
| V7 | 6AL5 | Video Detector – Automatic Gain Control Diode |
| V8 | 6AU6 | Video Amplifier |
| V9 | 6AU6 | Ratio Detector Driver |
| V10 | 6T8 | Ratio Detector – Audio Amplifier |
| V11 | 6AU6 | Sync Clipper – D.C. Restorer |
| V12 | 6SN7GT | Vertical Sweep Output |
| V13 | 6SN7GT | Vertical Sweep Oscillator |
| V14 | 6SN7GT | Horizontal Sweep Output |
| V15 | 6SN7GT | Horizontal Sweep Oscillator |
| V16 | 5V4G | Low Voltage Rectifier / Voltage Doubler |
| V17 | 6X5GT | B Minus Rectifier |
| V18 | 6V6GT | Audio Output |
| V19 | 12AU7 | R.F. High Voltage Oscillator |
| V20 | 1B3GT | High Voltage Rectifier |
| V21 | 7JP4 | 7″ Picture Tube |
References:
Antique Trader Radio and Television Price Guide, Kyle Husfloen, Editor, 2005