Western electric 264 c schematic

Page 1

Western Electric Company

No.264-C VACUUM TUBES

Classification-Small. low noise, filamentary triode

The 264C tube tepla s the 2643. it includes :1 new mcchziniczil design and an imprmed
filament. The electrical clmrzxcte s are identical with those of the 264B tube except for a lower
average microphonic level, and :1 slight change in the interclectrode ctlpacitzlnces.

ApplicatiOn-Audioifrequency amplifier particularly where exceptionally low tube noise or
exceptionally high-input resistance are required.

Dimensions-Dimensions, outline diagrams of the tube and base, and the arrangement of the
electrode connections to the base terminals are given in Figures 1 and 2.

Base-Small, four-pin thrust type, with pins silver-plated.

Socket-Standard, founcontact type> preferably with contacts silver-plated, such as the Western
Electric 143B socket

Mounting Positions-This tube may be mounted in any position.

Copyright 1937 Western Electric Company, Incorporated

7294,

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Wesrem Electric Company

No.264-C VACUUM TUBES

Average Direct Intereleetrode Capacitances

Gridtoplate.... . .. ..... 4.9;.tnf.
Grid to filament. . .. .. .. . . . . .. .. . . 3.2 apt,
Plate to filament .......... .... . .,. VVVVV . ... . 2.2 Hit.

Filament Rating

Filament current. .. . .. . . . . ... .,, 0.300 ampere, d.c.

Nominal filament voltage. . ., . .... . . . .. ., 1.5 volts

The filament of this tube is designed to operate on a current basis and should be operated at as near
the rated current as is practicable.

Characteristics-Gil(Lplate characteristics of a typical 264C tube are shown in Figure 3 for
several values of plate voltage. Corresponding amplification factor, plate resistance, and trans
conductance characteristics are given in Figures 4, 5 and 6, respectively, Plate characteristics for
several Values of grid bias are shown in Figure 7. in each case, the grid and plate voltages are
measured from the negative end of the filament.

Operating Conditions and Output-Permissible grid and plate voltages are included within
the area, ABCD, in Figure 3. Values of amplification factor, plate resistance, and transconductance,
and typical performance data are given in the table {or recommcnded and maximum operating
conditions represented by selected points within this area. Recommended conditions or others of
no greater severity should he selected in preference to maximum conditions wherever possible. The
life ofthe tube at maximum operating conditions may he shorter than at the recommended conditions.

The performance data include the fundamental power or voltage output and the second and
third harmonic levels for the indicated values of load resistance The fundamental output is given
in terms of the power, Pm, in milliwatts, for values of load resistance, R, equal to and double the
value of the plate resistance, rp, and in terms of the voltage, Epm, in peak volts, for xalues of load
resistance five times the plate resistance. The second and third harmonic levels, 172, and Fgm, are
given in decibels below the fundamental in each case, '1 he peak value of the sinusoidal input voltage,
Egm, is numerically equal to the grid bias For each operating condition. Fora smaller input voltage,
Eg, the fundamental power and voltage output and the harmonic levels are given approximately
by the following relations:

P:Pm 13 >
aw

i:

r, :E m i

P p Egm

F2=F2m + 20 logic f-m

'B

F3=F3m + 40 logmf