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New Receiving Valves

Wireless World, June, 1947.
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First details of Mazda and Mullard ranges.

Most of the new types announced by Mazda will be on the BVA type B8A base described in our issue of last November. The AC/DC series, already in production, has a standard heater current rating of 100 mA and includes the following types. Unless otherwise stated the bulb diameter is 20 mm

Mazda 10C1, 10F9, 10LD11, 10P13, 10P14 & U404.


Triode-heptode frequency changer. Performance equivalent to that of the Mazda TH233 that is IO based.


Pentode RF amplifier primarily designed to work in the IF stage of a receiver: working mutual conductance, 2.4 mA/V. Similar to the VP133, but is designed to work with the same operating potentials on input grid and screen grid as the 10C1. This enables the number of resistors and capacitors in the receiver to be reduced.


Double-diode-triode, the triode section of which has a voltage amplification factor of 30.


Beam power output pentode intended primarily for use in receivers where the saving of space is of the first importance. The 10PI3 has been especially designed to enable resistance smoothing to be employed in anode and screen circuits. With 180 Volts on the anode and 165 Volts on the screen it has a power output of 2.5 Watts.


Beam power output pentode with greater power-handling capacity than the 10P13. It is fitted with an international octal base and has a bulb 28.5 mm in diameter. Typical operating voltages are 165 Volts on the anode and 175 Volts on the screen, under which conditions the power-handling capacity is 3.3 Watts.


Half-wave rectifier designed for input voltages up to 250 Volts RMS DC output 90 mA.

In the forthcoming AC range, 6.3 Volt heaters with reduced current consumption will be standardized, and small-bulb construction will be used wherever possible. The types which will be available are as follows:-

Mazda 6C9, 6F15, 6LD20, 6P25, 6F13 & 6L18.


Triode-hexode frequency changer similar to the TH41.


Variable-μ RF pentode designed for operation in conjunction with the 6C9 using common AVC bias and coupled screens.


Double diode triode; amplification factor of triode section 30.


Beam power output pentode; with 250 Volts on the anode and screen, gives a power output of 5.8 Watts. It is fitted with an international octal base and has a bulb diameter of 45 mm.


High-gain screened RF pentode for wide-band reception, e.g., in television.


Triode designed primarily for use as the local oscillator in superhet television receivers. It is an efficient oscillator up to 150 MHz.

The spigotless type B8A base has been adopted for the new 'U40' range of Mullard valves.

The new range of Mullard valves to be released later in the year will be fitted with the spigot-less version of the BVA type B8A base and will be made by a new low temperature sealing process in which a special cement is used to join the bulb to the glass base. Advantages claimed for the method are that softening and distortion of the base are avoided and hard connecting pins can be used. There is also less risk of 'poisoning' the cathode.

The new valves will have a diameter of 22 mm and lengths ranging from 66 to 84 mm. The heater current will be 100 mA and the following details of representative types have been received.

Mullard UAF41, UCH41, UL41 & UY41.


Single-diode-pentode: only one diode is included in order to avoid interaction between the diodes in a circuit where two diodes are required. By using two UAF41 valves in a receiver, the diode section of the IF valve can be used for detection and the diode section of the AF amplifier for AVC In this way the delay voltage of the AVC valve will not be affected by the control of the IF amplifier. The slope of the UAF41 is 1.8 mA/V and the anode-grid capacitance is less than 0.002 pF.


Triode-hexode: The third hexode grid is connected internally to the triode grid and the valve can therefore be used only as a frequency changer. The heater consumption is only 1.4 Watts and the characteristics of the UCH4I are approximately the same as those of the earlier CCH35.


Output pentode: This valve has a mutual conductance of 9.5 mA/V, and is capable of delivering 4.2 Watts of AF power into a 3,000 Ω load when operated at anode and screen voltages of 165 Volts, and with a signal input of 6.2 Volts. The valve is so designed that, with the obvious exception of the resistance in the heater circuit, the circuit constants, i.e., cathode and screen resistances and anode load are substantially independent of the supply voltage.


Half wave rectifier: This valve is designed for input voltages up to 250 Volts RMS and gives a rectified output current up to 90 mA.

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