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Some Important British Valves

This selection is taken from: The History of the British Radio Valve to 1940 by Keith R Thrower. 1004

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C. Marconi 1913
R. 1916
Q. Marconi 1916
FE1. M-OV 1920
DER. M-OV 1922
AR.06. Ediswan 1923
"Wuncell' W series. Cossor 1924
PM4. Mullard 1925
KL1. M-OV 1927
AC/R & AC/G. Cosmos 1927
S625. M-OV 1927
PM22 & PM24. Mullard 1928
PX4. M-OV 1929
SV4. Mullard 1929
AC/Pen. Mazda 1930
MS/PenA. Cossor 1930
VMS4. M-OV 1931
AC/DD. Mazda 1932
MHD4. M-OV 1933
PM2B. Mullard 1933
VHT4. Ferranti 1933
"Catkin' MPT4. M-OV 1933
QP21. M-OV 1934
FC4. Mullard 1934
ACFC & FC2. Lissen 1934
AC/TP & TP22. Mazda 1934
H11 & L11. M-OV 1934
HA1. M-OV 1936
TSP4. Mullard 1936
TV4. Mullard 1936
D1. Mazda 1937
KT66. M-OV 1937
EE50. Mullard 1938
EF50. Mullard 1939

C - Marconi 1913

C. This was a soft triode valve with a lime-coated platinum filament, designed by H J Round of the Marconi Company and manufactured by Edison Swan. Other valves of similar construction were the CA, LT, N, T and TN.

R - 1916

R type. British version of the 'French' hard vacuum triode, having a pure tungsten, bright emitter filament. This valve and many of its variants, some gas filled, were produced by most British manufacturers. Later valves with similar characteristics, were the Cossor P1 and P2 (which had arched filaments, fan shaped grids and helmet-shaped anodes), the Ediswan AR and Mullard ORA. Higher power variants of the R valve were produced for driving loudspeakers, such as the LS series of M-OV (LS5, LS5A, LS5B, LS6A & LS9B) and the PA series of Mullard.

Q - Marconi 1916

Q. A bright emitter triode of small dimensions having widely shaped lead-outs to minimise inter-electrode capacitance. It was a high impedance valve, used primarily as a detector. Like all early Marconi valves, it was made originally by Edison Swan (Q), but after 1919 by M-OV. Amongst the first valves produced by Marconi-Osram in 1919 was the V24 which resembled the Q except that it had a lower impedance for use as an RF or low power AF amplifier. The later DEQ was a high impedance detector.

FE1 - M-OV 1920

FE1. A bright emitter, four-electrode valve of similar appearance to the Q, although larger. Marconi-Osram also produced the FE2 which was a smaller version of the FE3, and the FE3 which had a four-pin base with a side screw terminal for the space-charge grid.

DER - M-OV 1922

DER. First thoriated tungsten, dull emitter triode to go into volume production in Britain. An earlier version of this, the LT1, went into small-scale production in 1921. Valves of similar type were the Ediswan ARDE and Mullard D.3. A year or two later various dull emitter output valves appeared, such as the Ediswan PV series, the Marconi-Osram type LS5 and the Mullard DF series, eg DFA3 & DFA8.

AR.06 - Ediswan 1923

AR.06. A dull emitter valve having a filament of the so-called 60 mA class for operation from two dry cell batteries. Similar types were the Marconi-Osram type DE3 and the Mullard type DF.ORA and BTH B5.

"Wuncell' W series - Cossor 1924

"Wuncell'. First oxide-coated filament valves of British design. Valves in this series included the W1, W2, W3, WR1 and WR2. The oxide coating proved to be unreliable.

PM4 - Mullard 1925

PM4. First successful oxide-coated filament valves of British manufacture (but based on Philips patents and design). Within a year the PM range was extended to about eight types. Later in 1926, Cossor replaced the "Wuncell' range with their successful "point one' and "Stentor' series of valves.

KL1 - M-OV 1927

KL1. First indirectly heated triode valve for AC mains operation. The KL1 was an output valve; but also introduced by Marconi-Osram about the same time was the general purpose type KH1. Owing to poor heater-cathode construction, the valves required seven Watts of heater power and were soon replaced by more efficient types.

AC/R & AC/G - Cosmos 1927

AC/R & AC/G. Indirectly heated output and general purpose valves using the patented slip-coating process invented by E Y Robinson of Metrovick. The construction provided a long thin cathode with good thermal conduction to the internal heater, as well as good electrical insulation between the two. The heater requirements were 4 V and 1 A, which set a standard used by all British manufacturers for many years to come.

S625 - M-OV 1927

S625. Designed by H J Round (of the Marconi Company), this was the first British screened grid valve. It had a 6 V thoriated tungsten filament. Within a short time screened grid valves became available from all the leading British manufacturers, the most popular had 2 V oxide-coated filaments.

PM22 & PM24 - Mullard 1928

PM22 & PM24. First British Pentode valves, both for use in the output stage of audio amplifiers. The valves were first produced by the parent company, Philips, in Holland.

PX4 - M-OV 1929

PX4. Directly heated output triode for AC mains operation. Also Cossor 600T, Mazda P650, Marconi-Osram LS6A and Mullard AC044. Before this class of valve was introduced, battery types such as the M-OV P625 and Mullard PM256 were used in AC mains receivers.

SV4 - Mullard 1929

SV4. Indirectly heated screened-grid valve. Also Cossor MSG41, Marconi-Osram MS4 and Mazda AC/SG.

AC/Pen - Mazda 1930

AC/Pen. Indirectly heated output pentode. Success of the valve resulted from the use of the slip-coated cathode which enabled a high mutual conductance to be achieved without serious grid emission.

MS/PenA - Cossor 1930

MS/PenA. First RF pentode. The valve had a low anode impedance and was little used. The main wave of RF pentodes did not appear until 1933. These included: Cossor MS/Pen, Mazda MSP4 and the Mullard SP4.

VMS4 - M-OV 1931

VMS4. Variable-mu screened tetrode. Also Mullard VS4, appeared in 1933.

AC/DD - Mazda 1932

AC/DD. Double diode for detector and AGC applications in superheterodyne receivers.

MHD4 - M-OV 1933

MHD4. Double diode triode. Also Ferranti HD4 and Mullard TDD4.

PM2B - Mullard 1933

PM2B. Class B output valve which combined two matched triodes in a common envelope. Also Cossor 240B, Mazda PD220 and Marconi-Osram B21.

VHT4 - Ferranti 1933

VHT4. Heptode frequency changer based on the Sylvania type 6A7.

"Catkin' MPT4 - M-OV 1933

MPT4. Also MS4B, VMS4 and MH4. A range of valves with an external anode which formed the upper part of the sealed envelope. The lower part was of glass with the pins sealed into the foot.

QP21 - M-OV 1934

QP21. Quiescent push-pull output valve. Two matched pentodes in a common envelope. Also Mazda QP230 & QP240.

FC4 - Mullard 1934

FC4. Octode frequency changer.

ACFC & FC2 - Lissen 1934

ACFC & FC2. Triode hexode frequency changers of continental manufacture. British made types did not appear until 1935-6: these included Cossor 41STH, Mazda AC/TH1, Marconi-Osram X31 & X41, and Mullard TH4, TH13 and TH13C.

AC/TP & TP22 - Mazda 1934

AC/TP & TP22. Triode pentode frequency changers. Also Mullard TP4.

H11 & L11 - M-OV 1934

H11 & L11. Two miniature triode valves for use in deaf aid amplifiers.

HA1 - M-OV 1936

HA1. Acorn triode based on RCA design. Also Mullard AT4 (triode) and AP4 (pentode).

TSP4 - Mullard 1936

TSP4. RF pentode, having a high mutual conductance, designed for use in television receivers.

TV4 - Mullard 1936

TV4. "Magic-Eye' tuning indicator.

D1 - Mazda 1937

D1. Miniature, low capacitance diode for use as a vision detector in television receivers.

KT66 - M-OV 1937

KT66. Beam output tetrode. Of similar characteristics to the RCA 6L6 which first appeared in 1936. The KT66 previously had the type reference N66. Also introduced by Marconi-Osram about the same time was the N63, whose reference was changed to KT63.

EE50 - Mullard 1938

EE50. Secondary emission pentode. A valve of high mutual conductance for use in television RF amplifiers. The valve was of "all-glass' construction with the pins sealed directly through the foot.

EF50 - Mullard 1939

EF50. RF pentode of high mutual conductance for use in television RF amplifiers. It had "all-glass' construction.

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