Wireless World
Explanation of the Tables
THE INFORMATION GIVEN refers to the main electrical characteristics of
valves together with their base connections. Physical dimensions are not
included since there is a limit to the amount of information which it is
practicable to give, and size is only occasionally an important factor in
the choice of a valve.
The valves are classified under main headings according to their type. In
each section they arc divided according to their make and then
sub-divided into obsolete, replacement and current types. The tables are
largely self-explanatory, but the following notes should be read
carefully if the tables are to be fully understood.
Limitations of space necessarily restrict the amount of information which
can be included in these tables, so designers requiring more detailed
information should consult the valve manufacturers' published literature.
Also to economise on space a valve listed by a particular manufacturer as
"obsolete" may not appear under that manufacturer's name, but will appear
under another manufacturer's heading.
FREQUENCY-CHANGERS
Valves in this section are intended primarily for use as frequency-
changers in superheterodynes and the figures-given are the normal
operating conditions for this application. Some of the valves included
are occasionally used for other purposes. however, and the voltages and
currents may then be very different. Even in their normal application
differences may be found in individual receivers, since not all designers
adopt the "normal" conditions: this is particularly so on short-wave
bands. It is to be noted that some valves which do not include an
oscillator section, and which thus apparently require a separate
oscillator can actually be used as complete frequency-changers by using
an oscillator circuit coupled between cathode and another electrode.
SCREENED TETRODES AND PENTODES
The main application of valves in this section is to r.f. and i.f.
amplification and the operating conditions are normal ratings for this
condition. No distinction is made between tetrodes and pentodes because
in most cases the type of valve is immaterial as long as its
characteristics are otherwise suitable. It s only important in special
applications, where separate use is made of the suppressor grid, and then
the normal characteristics are in any case insufficient to enable a
choice of valve to be made. Except where the suppressor grid (g3) is
internally connected, it is possible to determine whether a valve is a
tetrode or a pentode by reference to the valve-base connections.
Some of the valves in this section are also listed under Amplifier
Triodes. The characteristics given there are obtained with the screen-
grid connected to the anode.
Many of the valves are suitable for use in R-C-coupled a.f. amplifier
stages. When so used the voltages applied to the electrodes and the
currents obtained are very different from the r.f, amplifier condition.
They cannot readily be given, however, since they are as much a property
of the circuit values as of the valve.
OUTPUT VALVES 1
Triodes, beam tetrodes and pentodes are all included here with normal
maximum operating conditions as output valves for single-valve Class-A
operation for a.f. application. They are distinguished by the letters
(T), (BT) and (P) following the type number and those containing other
systems have additional letters (SD), (DD) and (T) for single or double
diode and triode, respectively.
A few contain the elements of an h.t. rectifier in addition and these are
distinguished by the letter (R).
In some cases the conditions for a tetrode or pentode operating as a
triode with the screen-grid joined to the anode are also given. This
condition can be distinguished by the absence of a figure for screen
voltage, but in addition the letter (T) placed after the type number
indicates that the conditions are those of a triode. The fact that the
electrode structure is that of a tetrode or a pentode is obvious as the
valve appears in another row followed by letters (BT) or (P).
Even under Class-A conditions the anode and screen currents rise with the
signal input to a small extent. The anode current with full drive is
about 2 per cent greater than the quiescent value. With some valves the
screen current increases much more and may become as high as three or
four times the quiescent value. This increase is usually greatest when
the valve is of a type drawing a very low quiescent current.
Since there is no standard method of rating valves, the figures quoted in
the tables are sometimes for the no-signal condition and sometimes for
full drive. It is believed that most of the figures for British valves
are for no-signal. whereas most of those for American types are for
maximum applied signal.
The matter is mentioned chiefly to explain small differences which may
exist between the figures given here and those which may be found in
other lists. The differences are, in practice, unimportant for they are
less than the normal variations between individual specimens. of the same
type.
Because of the rising current with drive there is a slight difference in
the output powers obtainable with fixed grid bias on the one hand and
cathode bias by a resistor on the other. Figures for battery-type valves
are invariably for the fixed-bias condition. For other valves there may
be some discrepancies since again there seems to be no standard procedure
for indicating output. The difference is not large, however, and can be
ignored for most purposes. In general the output with cathode bias is up
to 10 per cent less than with fixed bias.
The maximum resistance which may safely be included in the triode-to-
cathode external circuit depends on the method of obtaining grid bias.
With valves taking more than about 20 mA cathode current it is a safe
rule to limit the grid resistor to 0.5 M for cathode-bias and 0.1 M
for fixed bias.
In individual cases and under particular operating conditions it may be
safe to exceed these figures, but this should not be done without close
investigation.
OUTPUT VALVES 2
The conditions included here are those for push-pull operation of a.f.
output stages. Five modes of push-pull are recognised and distinguished
in the "Class" column; they are A, AB1, AB2, B1 and B2. In Class A both
valves are conductive over the whole input cycle and the anode current
with full drive is substantially the same is that with no drive. In Class
AB the valves are worked individually under non-linear conditions and may
be individually cut-off over a small part of the input cycle and the
anode current for full output is appreciably higher than that with no
input. In Class B each valve is cut off for about one-half of the input
cycle and the anode current at full output is much greater than that with
no input signal. The subscripts 1 and 2 show that operation is
respectively without and with grid current. The anode and screen
currents quoted for Class-A and -AB operation are with the maximum input
signal voltage the currents for Class-AB2, -B1 and -B2 operation,
however, are subject to considerable variation with input, so it is more
useful here to give figures for the quiescent conditions. With Class-AB
and -B operation the manufacturer's literature should, in any case, be
consulted.
For Classes AB2 and B2, the minimum grid-to-grid input resistance is
given. The figure, together with that of the input voltage, is necessary
for the design of the driver stage.
The valves included in this section fall into two groups. One consists of
double triodes and double pentodes intended mainly for Class-B1 and
Class-B2 operation. They are chiefly battery types which used to be
designated as q.p.p. and Class-B stages. There are also a few indirectly-
heated-cathode types (for example 6A6) which have other applications -
these last will also be found in the appropriate section (usually
Amplifier Triodes) with the figures appropriate to one section of the
valve as an amplifier.
Figures for anode and screen currents are quoted per-valve (or per unit
in the case of double valves) and in some cases several sets of different
figures are given for the same valve under different conditions. Apart
from double valves, most of the valves in the section appear also in
Output Valves I, and to distinguish between pairs of valves and double
valves, which may not be listed elsewhere, the heater current figures are
given only for double valves (unless otherwise stated). The figures for
the others are obtainable from Output Valves 1.
Very few Class-A conditions are given because they are usually obtainable
directly from Output Valves 1. For push-pull Class A the currents and
anode-to-anode load are normally twice the figures for single-valve
operation. The power output for the same odd-order distortion is usually
a little more than double.
The differences between fixed-bias and cathode-bias are considerable
under Class-AB and Class-B conditions. Where no value is quoted for a
bias resistor it is to be understood that operation with a fixed bias
is required where a bias-resistor value is given, the other figures refer
to cathode-bias operation. With fixed bias, it is usually necessary for
the bias source to be of low impedance; with positive drive it is
essential.
The value of bias resistor quoted (RK) is that required per valve, or per
unit in the case of double valves.
OUTPUT VALVES 3
The valves in -this section are designed to withstand short-duration
high-voltage peaks and the figures given are for television line-scan
output-stage working.
The amount of information provided in this section is necessarily
limited, and operating conditions vary so widely with circuit application
that in all cases of doubt the manufacturer's literature should be
consulted.
THERMIONIC DIODES
The main characteristics required to be known about a diode are given
here. Some of the double types have a common cathode. whereas others have
separate cathodes. These can be distinguished by reference to the valve
base connections. Some guidance to the internal resistance of a diode is
given by the column giving the maximum rectified current: high-current
types are invariably of lower resistance than those for low current.
Multiple valves which include diodes are not listed here but will be
found under the section appropriate to the main assembly of the valve
that is, Screened Tetrodes and Pentodes, Amplifier Triodes and Output
Valves 1.
SEMICONDUCTOR DIODES
This section includes copper-oxide, selenium, germanium and silicon
diodes with ratings not exceeding 300 PIV and 100mA maximum rectified
current, i.e. the devices listed here are intended mainly for signal
operation rather than power rectification (although many can be used as
low-power rectifiers). Other diodes are listed in the Semiconductor
Rectifiers (silicon and germanium) and Metal Rectifiers (copper oxide and
selenium) sections, except when the inclusion of a particular device
there would obviously be wrong - the G.E.C. Type SCVI, for instance, is
designed for use as a voltage-dependent capacitor. Maximum ratings are
given and in one column typical applications are listed.
JUNCTION TRANSISTORS
Unless otherwise stated, parameters are given for a temperature of 25 C.
Comparisons between various types should be made only at the same
temperature: in cases of doubt fuller data should be consulted but, in
general, the major effects of elevated temperature are to reduce the
permissible dissipation and increase the collector leakage current Ico
(This approximately doubles for each rise of 10 C and can affect bias
conditions with unsuitable circuit arrangements. Other characteristic
changes which take place with temperature are of a relatively minor
magnitude and in many cases may be ignored.
The figure for Vc max should never be exceeded in normal use. In many
circuits the maximum allowable h.t. rail voltage will be half this
figure.
The small-signal parameters chosen for tabulation are the conventional
equivalent-T network ones for the common-emitter configuration. This is
by far the most common circuit arrangement in use with junction
transistors. Corresponding figures for common-base and common-collector
arrangements are easily derived.
The collector voltage and current at which the small signal parameters
are given is defined. This is important since some of the parameters vary
considerably with the bias point. In particular there is a large
increase in re with decreasing Ie.
The figure for alpha cut-off is for the common base configuration and is
lower by a factor of approximately a' for the common-emitter arrangement.
No attempt is made to specify large signal behaviour. In general the
most important departures from the figures quoted for small-signal
conditions are likely to be decreased re and decreased a'. The table on
Page 2 explains the symbols used.
AMPLIFIER TRIODES
The conditions given are those pertaining to operation as transformer-
coupled a.f. amplifiers at maximum rating, which is the most suitable
condition for comparing valve characteristics. Conditions for R-C
coupling depend too much upon the circuit constants to be useful. At the
reduced voltages normally applied to the electrodes with R-C coupling,
the a.c. resistance and mutual conductance are usually 20 to 50 percent
higher and lower respectively than the figures listed.
SMALL TRANSMITTING VALVES
All categories are included in this section (triodes pentodes, beam
tetrodes, etc.) having up to 50 watts anode dissipation. The figures
given are for Class-C r.f. amplification on telegraphy. It should be
noted that in the case of double valves (identified by letters (DT),
(DBT), etc., in the "Type" column) the figures for anode, screen and
grid currents, dissipation and output refer to the pair.
Regarding the operating frequency column, the figures under "Reduced
Rating" can generally be taken to be the maximum frequencies at which the
valves will give a useful power output. As the efficiency of a valve
decreases at these higher frequencies, it is necessary to make some
reduction to the ratings (or power input) in order to ensure that the
power dissipated in the valve does not exceed the safe limit. The
percentage reduction varies from valve to valve, however, so it is
advisable to consult the manufacturer's literature if the reduced ratings
are required.
VALVE RECTIFIERS
Included in this section are types which have simultaneous ratings up to
10kV peak inverse and 500mA maximum rectified current. Valves designed
for the production of e.h.t. supplies (i.e., over 1kV at less than 3OmA
or so) will be found in the E.h.t. Rectifier section.
The ratings given are maximum ones and assume a supply frequency of 50
c/s. In some cases a higher current output is permissible if the input
voltage is reduced and in nearly all cases the input voltage can be
considerably increased and the output current slightly increased if the
rectifier is followed by a choke-input filter instead of the usual
reservoir capacitor.
The figure for minimum resistance can be reduced if a smaller reservoir
capacitor is used. When an input transformer is used, this resistance is
usually provided by the resistance and leakage reactance of its windings,
but in transformerless circuits sufficient resistance must be provided to
limit the peak current.
Figures for the mean unsmoothed output voltage are not given, since they
depend on the current and reservoir capacitance as well as the valve.
With no current drain the voltage reaches 1.414 times the r.m.s. input
voltage and this figure should be taken for the Voltage rating of the
reservoir capacitor. At maximum current the output voltage is
approximately equal to the r.m.s. input voltage in the case of rectifiers
of 60 mA and upwards current rating.
METAL RECTIFIERS
Copper oxide and selenium rectifiers are both made in basic units of low
voltage rating and in various sizes for different currents. Different
voltages are catered for by stacking together various numbers of the
basic units and there are also different stacking methods for units for
use as half-wave, full-wave, voltage-doubler and bridge rectifiers. The
total number of rectifier assemblies possible with only a few basic,
units is thus very large. In order to reduce the numbers, therefore, a
few examples are listed as guides and from these the other possible
ratings can be deduced.
SEMICONDUCTOR, RECTIFIERS
The devices listed here have ratings which exceed 300 PIV and l00 mA
maximum rectified current and they are thus more suited to power
rectification. However, this is not their only use - many are suitable
for use in magnetic amplifier circuits etc. Some details of rectifier
stacks are included.
E.H.T. RECTIFIERS
Used mainly for the production of the high-tension supplies for cathode-
ray tubes, thermionic diodes and metal rectifiers listed here are capable
of producing supplies of over 1kV at currents of less than 30mA.
Rectifiers capable of producing high-voltage high-current supplies (i.e.
for transmitter h.t.) are listed in the Valve Rectifiers section. Three
methods of e.h.t.-supply production are recognised in the data. First,
the "rectification" of the high-voltage pulse appearing at line-flyback
time in a television receiver: here the ratings assume a pulse duration
of about l0usec. Secondly, the rectification of the output of an r.f.
oscillator (100 kc/s and upwards) and, thirdly, by rectification of a
low-frequency supply (possibly derived from the mains-via-a step-up
transformer). Characteristics for this last case are marked by relatively
large values for the reservoir capacitor.
TELEVISION CATHODE-RAY TUBES
All the tubes in this section are designed for magnetic deflection. It
should be noted that the figure given for deflection angle is the number
of degrees subtended by the picture diagonal. Although the diagonal of
the screen is given as a round number of inches, this should not be taken
literally as there are slight variations, between tubes.
OSCILLOSCOPE CATHODE-RAY TUBES
Data given under this heading in previous issues of the hook have covered
a very wide range of c.r.ts, including radar, instrument, and
e.s.-deflection television tubes. Due to this diversity, inadequacies in
the presentation occurred. Thus, in this edition, the data given
previously have been replaced by a directory of manufacturers of
"special" cathode-ray tubes.
EFFICIENCY DIODES
The purpose of these diodes, applied to television line-scan circuits, is
to provide a section of the line-scan sawtooth waveform from the energy
stored in the deflector coils during the flyback, thereby reducing the
amount of anode current required in the line-scan output stage. The
thermionic diodes here may also be found under Valve Rectifiers, and from
the latter section it will be apparent whether they are single or double
diodes.
Where only one unit of a double diode can be used as a damping diode,
this is made clear by a note.
AMERICAN TYPES
Valves listed as "American" require some explanation. The type number of
many American valves consists of two figure groups separated by a letter
group (for example 6L6). Many of these have a following letter group
also to distinguish different physical forms of electrically similar
valves. These following letter groups do not appear in the tables; only
the basic number is listed.
Among the octal-based types the last letters usually have meanings as
follows:-
No letter; metal valve; for example, 6L6.
MG; metal-glass; for example, 6L6MG.
G; glass; for example, 6L6G.
GT; glass tubular; for example, 6L6GT.
The majority of American-type valves in use and available or manufactured
in this country are the G and GT types and should be ordered by appending
the appropriate letters to the type number as listed in the tables. For
replacement purposes it is important to distinguish between the G and GT
types, since the former is much larger physically. Electrically all are
usually interchangeable but there are small differences of inter-
electrode capacitance which may necessitate re-trimming when types are
substituted in r.f and i.f. circuits.
Many newer types are only available in one form and never have following
letters.
Many American-type valves are made in this country and are available
under the American Type numbers. These are listed under the names of the
British firms concerned -
It may be mentioned also that the American 7- and 14-series valves are
listed as having 6.3V and 12.6V heaters respectively as these are, common
operating conditions. These valves also have maximum ratings of 7V and
14V, and can be used for car radio where the high maximum rating is
adopted to suit the voltage of a battery on charge.
"SPECIAL QUALITY" VALVES
These valves are generally improved versions of existing types, designed
for operation under more severe conditions than found in ordinary
domestic receivers. The description covers several classes of
improvement, such as long life, resistance to mechanical shock,
electrical stability and various combinations of these. It also includes
the improved valves hitherto known as "reliable" valves. No distinction
is made in the tables between these various classes, however. The valves
are bracketed with their ordinary equivalents and are indicated by the
abbreviation "SQ" alongside.
GROUPING
The valves are grouped within their sections as Obsolete, Replacement and
Current Types and this has been done in accordance with the
recommendations the manufacturers concerned.
These terms are used in the following senses:-
Obsolete : Valves which are no longer manufactured and which are normally
unobtainable. The list is obviously incomplete, since it is impracticable
to include all valves back to the first ones ever made! The object has
been to include only those types which may still be in use in old sets to
assist, by giving their characteristics, in the choice of the most
suitable replacement. Isolated specimens may, of course still be
obtainable.
Replacement : Valves which are no longer manufactured in large
quantities, but of which so many are in use that small hatches are still
made for replacement purposes. They are normally still obtainable but may
have to be specially ordered and may be subject to temporary delay. They
are valves no normally to be recommended for use in new equipment which
is to be manufactured in any large quantity.
Current : These valves include the latest types and older ones which are
still being produced in quantity. The latter are usually more readily
available but may be expected to become replacement types soon.
It should be realised that all the groups really merge into one another
from the user's point of view. Particular obsolete valves may be easily
obtainable for a time; individual replacement valves and even some
current types may he quite hard to.
INDEX, BASES AND EQUIVALENTS
On account of the large number of devices included - roughly 4,000
British and 1,000 American type - an index is provided to assist in
finding them quickly. All items are listed in alphabetic and numerical
order of their type numbers in the index (figures precede letters) and
against each entry is the page number (or numbers) where it can be found.
Also against each valve are base connections and a list of its
"plug-in" equivalents.
Occasionally a valve may be listed, for example "10ABC see XY99" : in
these cases, the valves are usually identical and the first number
represents an alternative listing. Sometimes a valve listed by a
manufacturer as "obsolete" may not be found under that manufacturer's
name, provided that it appears elsewhere.
The information. which appears under manufacturers names has been
supplied by the individual valve manufacturers and collected into its
present form by the staff of Wireless World. The data on American types
has been collected from many sources, but notably from data lists
provided by the Radio Corporation of America.
Blanks in the columns indicate that the figures missing have been found
to be unobtainable. Every effort has been made to secure accuracy, and
proofs for the "named" sections have been passed by the manufacturers
concerned. There are over 50,000 sets of figures in the tables, apart
from the base connections, of which there are some 600 distributed among
33 bases. It hoped that there are no errors ; should any be found
Wireless World would be pleased to receive details.
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