013 CATHODE RAY OSCILLOSCOPE Type R6673 (c 1950)
013 CATHODE RAY OSCILLOSCOPE Type R6673 (c 1950)
Amalgamated Wireless (Australasia) Ltd. Type R6673 Serial Number 4 32*25*21 This early Australian made oscilloscope has a 2 inch Cathode Ray Tube display, with two amplifiers, one Horizontal and one Vertical. The oscilloscope has adjustable focus and intensity controls, and horizontal and vertical shift controls (controlling the dc bias on the plates). The CRO includes a timebase which could also be controlled (1-8 coarse switch plus a fine control) or externally synchronized. An external input can also be applied to the horizontal deflection.The CRO has 6 inputs, 3 for each pair of plates, including inputs to the amplifier or directly to the plates. The oscilloscope used the conventional method for displaying waveforms in the CRT, i.e. Electrons are emitted from a heated filament, accelerated and focused into a narrow beam. This is then passed through a set of orthogonal parallel plates, one vertical and one horizontal. The input voltage signal is placed on the plates causing deflection of the beam. An interesting property in this model is that no calibrations were made. The 2 inch screen is not big enough for any precision measurements to be made, and no calibrations were made on the knobs. Thus the CRO was used for viewing waveforms only, and not for measurements. Bandwidth was quoted as 30c/s to 12 kc/s. This model was constructed completely from tube technology and does not have a PCB. All connections were made through soldered wire, as was typical of that time.
References:
M.C.
043 THERMIONIC VOLTMETER (c1925) The Cambridge
Instrument Company/England/No.L26466
Moullin Patent No 105403 150H ´ 160W ´ 95D
Wooden box with black top and base. Glass window to read non-linear scale from 0.5-1.5. Two pairs of brass terminals above the window marked 'applied potential' and '6 volts'. Zero adjustment and clamping controls are below the window along with on/off and rheostat control dial. The first vacuum tube voltmeter which uses a 6 volt supply and a triode valve. The voltage to be measured is applied to the grid of the valve and when the circuit is balanced the net current is sensitive to this voltage. This current is measured using a Cambridge "UNIPIVOT" galvanometer. This instrument allows measurement of voltages in the range 0.5-1.5 volts only, which are displayed on the scale which is linear between these voltages.
References:
1.K.Lyall, The Whipple Museum of the History of Science Catalogue 8
L.B.
204 LEE DE FOREST DIATHERMY GENERATOR
Lee de Forest Laboratories, Los Angeles, Calif. Serial No. E-1080
41*29*34
A black plastic board with the controls and meters for DC plate current and RF current on it. The electronic circuit is right behind the control board. The case of this device is missing. The circuit has two triode valves, two diode valves, a transformer and some other components. They are mostly connected by copper strips. Cleaned by the Electronic Workshop. This device can generate a frequency of 18 MHz with power up to 250 watts. The filaments must be heated up 30 minutes before switching on the plates in the triode valves. The generator was made by the Lee De Forest Laboratories, L.A. The manufacturing date is unknown. It was used for surgery or therapy. Triode valve was invented by De Forest in 1906. He introduced a third electrode, called the 'control grid', to the two electrode diode. Before 1912, the triode was called Audion.
References:
1. A.L. Albert, Electronics and Electron Devices, Macmillan Company, New York, p.106.
T.C.
067PALEC VALVE TESTER Model VCT-V (c1935)
Paton Electrical Pty. Ltd., Sydney. 30*30*19 The tester is encased in a wooden stained box with various pin sockets for testing tubes and a milliammeter so measurements can be made of the plate current. Furthermore, there are switches for the zeroing of the milliammeter, for biasing of tubes and for the power to the unit. By placing the defective tube in the appropriate socket, selecting the power source input, i.e. AC or DC and throwing the biasing toggle switch to zero, the plate current can be determined via the milliammeter. When the value of plate current has been noted the biasing toggle switch is flipped to its biasing position and the plate current is measured again. Consulting the tube testing table for that particular tube,the condition of the tube can be judged. Valve radios were so popular in the early 1930's that even today, valve testers are still being used. References:
1. "Fred Paton: from screwdriver and pliers to purpose-built test equipment", Electonics Australia, Dec 1993, p42
A.H..
295 ASTROPHONE CRYSTAL RADIO RECEIVER (c 1920)
Amplifiers Ltd., England.
25*25*6
Housed in a wooden box lined with blue fabric in the lid. On the facade, there are dials for the 'tuning' of the circuit to the desired station and two plugs by means of which extra capacitance may be added. The headset consists of two black cylinders suspended in a steel spring frame. Incoming modulated radio waves set up voltages across the antenna which is connected to a tuning circuit which consists of a capacitor and variable inductor 'tuned' to filter out all but the frequency of a desired station. Contact between a metal wire and galena crystal rectifies the output signal to allow the headphones to respond to the audio frequency components of the modulation. The circuit has been designed to accept extra capacitance to extend the range of reception to lower frequencies. In spite of the name of the manufacturer, there is no amplifier involved, and the energy to drive the headphones comes out of the received signal. The simple but effective receiver is the predecessor to the modern Hi-Fi systems of today.
References:
1. J.Hill,Radio! Radio! fig 118 2. P.Lankshear, Electronics Australia, July 1994, p98 A.H.
323 VALVE FABRICATION DISPLAY (c 1950)
Amalgamated Wireless Valve Co. Pty. Ltd. Sydney/Melbourne
50*32*7
White painted frame with glass cover houses board displaying main components and steps in manufacture of thermionic heptode valve 6BE6. Developed extensively in the 1930's, electron valves (commonly referred to as electron tubes) were used in a wide range of applications including the circuitry of radios, transmitter/receivers, televisions and the first computers, before the advent of transistor technology. Our display specimen gives an insight into the 'heart' of early electronics showing the assembly of a thermionic heptode (7 electrodes) Super Radiation 6BE6 valve with seven electrodes, manufactured - as the name indicates - for use as an amplifier in radio technology. The main components of the electron valve displayed on the board are: heater element, cathode, grids 1 to 5, plate, micas, ring getter, base, cage assembly, bulb and a completely assembled valve. Electron valves work by generating electrons at the cathode which move in the direction of the positive anode allowing a current to flow. No current flows, however, if the anode is not positive and it is this characteristic that allows the valve to act as a rectifier of AC current. Grids placed between the cathode and anode impede and repel the flow of electrons, thus altering the characteristics of the valve and hence its applications. Common types of valves include the tetrode and pentode, with two and three grids respectively. Early valves were large and fragile, before the manufacturing of smaller ones. An electron valve will be destroyed if heated to more than 20°C above its maximum operating temperature. In their heyday electron valves were produced all over the world with manufacturing plants also here in Australia in Sydney, Melbourne and Adelaide. Today they are still found in high power systems, televisions and are valued by the military due to their ability to resist voltage pulses, such as that created by an atmospheric nuclear explosion, which in many cases will destroy transistors. An accompanying Phillips brochure to the display provides a thorough explanation of the manufacturing of electron valves.
References:
1. K. Henney, Electron tubes in industry, McGraw-Hill, NY, 1937.
2. G.W.A. Dummer, Electronic Components, Tubes And Transistors, Pergamon Press, Oxford, 1965, p.114-131.
3. J.J. DeFrance, Electron Tubes and Semiconductors, Prentice-Hall, 1958.
MT
VALVE 512 MARCONI TRANSMITTER MOCK-UP
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