Westerrr Electric 88A User manual

Westerrr Electric
AMPLIFIER
No. 88A
Weight--Approximately 760 Pounds
INDEX Page
GENERAL DESCRIPTION 1
DESCRIPTION OF CIRCUITS 3
INSTALLATION 6
TUNING PROCEDURE 11
MAINTENANCE 14
LOCATION OF TROUBLE 15
APPARATUS LIST 17
ILLUSTRATIONS;
Front View with Doors Open Figure 1
Schematic Figure 2
Wiring Diagram. Figure 3
Dimensional Diagram ... Figure 4
Calibration of Second Harmonic Shunt .. Figure 5
Instructions for Use
GENERAL DESCRIPTION
The Western Electric No. 88A Amplifier is a single-stage power amplifier
capable of raising the modulated output of a 50-watt ultra high frequency
radio telephone transmitter to 500 watts of carrier power. It may be adjusted
to operate on any frequency in the range from 30 to 42 MC. Provision is made
for operating it into a single open wire, a double open wire or a coaxial trans-
mission line. The amplifier is equipped with a mercury vapor rectifier and the
necessary transformers for plate and filament supplies. Approximately 4.6
KW of power is required from a 3 -phase 220-volt 50 or 60-cycle supply.
The components of this amplifier are assembled in a steel cabinet having
a welded structural steel frame. The meters are located on a panel at the top
Instruction Bulletin No. 746

of the cabinet behind a glass window. Directly below are two glass paneled
doors permitting observation of the amplifier tubes and providing access to the
radio frequency equipment. Centrally located on the front of the cabinet is a
control panel on which are mounted three screw-driver operated controls for
adjusting the grid input circuit, the neutralizing condenser and the plate
circuit. Two tumbler switches are also provided for controlling the power
supply circuits. Below this panel are two hinged metal doors providing access
to the lower portion of the cabinet where the rectifier and power equipment
are located. Safety switches are provided on all doors for the protection of
the operator. A horizontally mounted fan, located between the power and
radio equipment, provides ventilation by sucking air in through an opening
near the bottom and forcing it up through the set and out through perforations
at the top of the cabinet. The air entering the set is cleaned by a spun glass
filter covering the opening at the base of the cabinet.
Figure 1-Front View with Doors Open
[21

DESCRIPTION OF CIRCUITS
For purposes of discussion, the circuits of this amplifier shown on sche-
matic diagram Figure 2 and wiring diagram Figure 3, are divided into three
groups: radio-frequency, power-supply and control.
Radio-Frequency Circuits
Two Western Electric No. 251A Vacuum Tubes are used in a single neu-
tralized stage of push-pull amplification. The RF input terminals connect to
a coupling coil (L1) which is inductively coupled to a variable inductance (L2).
This variable inductance with the fixed condensers C2, C12, C13, and C14,
comprise the grid input tuned circuit. Grid bias voltage supplied from the
50-watt transmitter is applied to the grids of the tubes through a grid current
meter (M1) and two RF choke coils (L3 and IA). A filament transformer
(T3) supplies the filament power and condensers C5 and C6 by-pass each side
of the filament to ground.
Neutralization is accomplished by means of the balanced variable con-
denser C4 connected between the grids and plates of the opposite tubes.
The plates of both tubes are connected to a center tapped inductance
(L5) and a balanced variable condenser (C3). Plate voltage is fed into the
center of the inductance (L5) through an RF choke coil (L7) and a plate current
meter (M5).
The output circuit is conductively coupled to the antenna transmission
line by means of taps on the plate circuitinductance (L5). Blocking condensers
(C9 and C10) remove the DC potential from the transmission line and meters
M2 and M4 provide an indication of the RF current in the two transmission
lines. When a balanced two wire transmission line is used for connecting the
output to the radiator, it is connected to terminals 17 and 18, and a second
harmonic shunt similar to HS1 must be provided and connected to terminal
17. When the amplifier is used with a single open wire or a coaxial transmission
line transmission line meter (M4), blocking condenser (C10) and the corres-
ponding output coil tap are not used. Output terminal 18 which is located
on the same side of the transmitter as the connected coil tap, should be used
for a single open wire line and the transmission line running to the base in the
bottom of the set should be connected and used for terminating a coaxial
transmission line.
The harmonic shunt (HS1) connected between ground and output terminal
18 reduces the second harmonic to a negligible value. This suppressor consists
of a section of coaxial transmission line one quarter wavelength at the operating
frequency or one-half wavelength long at the second harmonic frequency and
is short-circuited at the far end. When correctly adjusted as described under
"Installation" it produces a short circuit across the. output terminal of the
amplifier to the second harmonic frequency and has negligible effect on the
fundamental frequency.
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Power Supply Circuits
Filament voltage for the amplifier tubes (V1 and V2) and the rectifier
tubes (V3, V4 and V5) is supplied from filament transformers T3 and T2
respectively. The 220-volt primary voltage for these transformers and the
200-volt grid bias voltage are obtained from the associated transmitter, where
they are adjusted to the proper value.
The plate supply consists of a 3-phase mercury vapor rectifier and a
single section filter. The primary windings of the three-phase high-voltage
transformer (T1) are tapped to provide adjustment of the high-voltage supply.
The center tap of the secondary of this transformer (T1) is connected to ground
through the coil circuit of an overload relay (S3). The high-voltage direct
current is indicated by a voltmeter (M3) and the current drawn by the amplifier
is indicated by an ammeter (M5).
Control Circuits
The control circuits of this amplifier operate in conjunction with some of
the circuits of the associated transmitter to provide the necessary sequence of
switching operations.
The power supply switch (D1) is a three-circuit main line switch for the
high-voltage rectifier. It supplies power to the contacts of relay S1 which
completes the primary circuit of the high voltage transformer (T1). The plate
supply switch (D2) is connected in series with the coil circuit of relay Si, which
is energized with power supplied from the associated transmitter when it is
operating. The contacts of the overload relay (S3) are connected in series with
the overload relay of the associated transmitter so that if either relay mo-
mentarily opens when the transmitter is operating, both equipments will be
turned off and cannot be started again until the plate control switch of the
associated radio transmitter is turned off and on.
The door switches (D3.1 to D3.5 inclusive) are connected to circuits in the
associated transmitter so that when any door is opened the high-voltage supply
in both units is removed.
Relays S2 and S4, and resistance R1 constitute a protective circuit for
reducing the initial charging current of the filter condenser (C1). Resistor
Rl is automatically connected in series with the filter condenser (Cl) while
it is being charged, thus protecting the rectifier tubes from a heavy surge of
current when the equipment is turned on. The relays operate as follows:
When the plate supply of the amplifier is turned on, the condenser charging
current operates relay S4 through resistor Rl. When condenser Cl is fully
charged, the charging current stops, relay S4 releases and relay S2 operates
and connects the negative terminal of the condenser (C1) to ground.
INSTALLATION
Dimensions of the amplifier and the location of terminal blocks are shown
on Figure 4. Sufficient space should be allowed around the amplifier, partic-

ularly in the rear, to provide free entrance of the incoming air, to facilitate the
installation of the power transformer (T1) and power supply wires, and to
enable the operator to remove the rear panel for cleaning the air filter.
The amplifier may be placed alongside the 50-watt transmitter and the
conduits placed underneath the floor. If the latter is impractical the equipment
may be raised up from the floor by wood spacers to provide room for the inter-
connecting wires. When this is done it is necessary to close all of the space
between the base of the amplifier and the floor so that air cannot be drawn into
the unit at this point.
R. F. Input Circuit
The input circuit of the amplifier should be connected to the output of the
transmitter by means of a length of Western Electric No. D-96800 Trans-
mission Line. A section of this line is connected to input terminals 19 and 20
and extends to the bottom of the amplifier as shown on Figure 4. The line
from the transmitter should be spliced at this point.
R. F. Output Tuned Circuit Inductance
There are four sizes of output tuned circuit inductances (L5) to cover the
complete frequency range from 30 to 42 megacycles. The correct one should
be specified when ordering (see apparatus list). When installing the coil the
lugs should be bolted to the terminals of the variable condenser (C3) and a
short length of No. 14 wire should be connected between the center tap of the
coil and the terminal on the stand-off insulator which supports the front end
of the RF choke coil (L7) located directly above the tuning inductance.
Transmission Line Current Meters
Since the output circuit is arranged so that either a high impedance (single
or double open wire) transmission line or a low impedance coaxial transmission
line can be used, two ranges of transmission line current meters are available.
0-3 ampere meters for transmission lines of approximately 500 ohms or 0-5
ampere meters for transmission lines of approximately 70 ohms impedance
should be specified when ordering. To install these meters it is necessary to
remove the meter panel heat shield inside the amplifier and the front glass
meter protecting panel. The heat shield is held in place by six screws around
its periphery and the glass panel by three flat head screws located in the upper
jamb of the glass paneled observation doors. These panels should be replaced
after the meters are installed.
Second Harmonic Shunt
The amplifier as supplied contains one coaxial transmission line type of
second harmonic shunt mounted on the left side wall of the cabinet and con-
nected to output terminal 18. This shunt when cut to the proper length as
described below is all that is required when a single conductor (coaxial or open
type) transmission line is used. When a two wire transmission line is used an
[ 7 1

2' I"
2I- INPUT TRANSMISSION LINE
Ì 6" I! DRILL
4 -HOLES
FRONT
BOTTOM VIEW
ANTENNA TRANSMISSION
LINE BOX
TERMINAL BLOCKS
FRONT
TOP VIEW
TERMINAL BLOCKS
ANTENNA TRANSMISSION
LINE BOX
ROLE FOR =ANTENNA
TRANSMISSION LINE
Figure 4-Dimensional Diagram
[8]
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additional second harmonic suppressor should be specified when ordering
(see Apparatus List). This shunt should be adjusted as described below,
clamped in the other side of the amplifier, and connected to terminal 17.
The suppressor should be adjusted to the operating frequency by cutting
it to the correct length. As supplied it is 86 inches long and the outer con-
ductor is notched every two inches. Remove the suppressor from the amplifier
and cut off the inner end of the spiral so that the remainder has a length as
specified on Figure 5. To do this cut through both conductors with a hack
saw so that the shunt is % inch longer than the required length and then cut
through the outer conductor alone at the prescribed point. This procedure
will enable the inner conductor to extend beyond the outer conductor. Thread
the knurled plug over the center conductor and force it into the end of the
tubing. Solder the center conductor to the plug and replace the suppressor in
the amplifier.
Transmission Line Connections
When a single conductor transmission line of the open wire or coaxial type
is used, only one coil clip in addition to the center tap on the tuning inductance
(L5) is required and the unused clip and lead should be removed from the
amplifier.
When a coaxial transmission line is used it should be run from the antenna
underneath the floor and be terminated at the junction box in the bottom of the
amplifier where the conductors should be securely spliced and soldered.
When an open wire, single or double conductor transmission line is used,
the section of "N -inch coaxial transmission line in the amplifier should be
disconnected from terminal 18. A single open wire transmission line should
be connected to terminal 18 and a two wire line to terminals 17 and 18 on top
of the amplifier.
AntennaThe length and type of the antenna to be used depends upon the radio
frequency employed, the service for which the equipment is to be used, and the
location of the transmitting site. For these reasons no specific constructional
details of the antenna are included in this bulletin.
GroundA copper strip located alongside of the terminal blocks is provided for
grounding the amplifier frame. This strip should be connected by means of a
similar strip to ground. For best results it should be connected to as good an
external ground as possible.
Transformers
The power transformer (T1) and retardation coil (L6) should be installed
after all wiring is completed. These units are shipped separately and should
be mounted as shown on Figure 1. The leads in the amplifier which connect
to these units are tagged and should be connected to the correspondingly
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30
29
2860 62 64 66 68 70 72 74 76 78 80
TRANSMISSION LINE LENGTH IN INCHES 82
Figure 5-Calibration of Second Harmonic Shunt
[ 10 1
84 86 88

numbered terminals on the transformer. Connect the three adjustable leads
of transformer T1 to terminal 6 of each primary winding. These are shown
on Figure 1 connected to terminal 2 of each primary winding.
Inspection
Before power is applied to the amplifier a careful check should be made
of the connections described above and of the interconnections described in the
instruction bulletin for the system. The amplifier should also be thoroughly
inspected and any loose connections that may have developed during shipment
should be tightened.
TUNING PROCEDURE
CAUTION: Remove plate voltage by opening the power supply switches
in both the 50 watt radio transmitter and No. 88A Amplifier
before adjusting or touching anything within the amplifier.
In tuning the amplifier for the first time it should be adjusted to operate
into an artificial antenna in order to check the output power, and obtain ap-
proximate settings for the controls. The antenna transmission line should
then be connected in place of the artificial antenna and the amplifier controls
readjusted.
An artificial antenna suitable for this purpose can be made by connecting
four 120 watt 110 volt lamps, preferably carbon filament lamps, in two parallel
strings of two lamps each. Sockets should not be used. The connections
between the tubes should be as short as possible and made by soldering heavy
wire directly to the lamp bases. If a two wire transmission line is used connect
the lamps between terminals 17 and 18 on top of the amplifier using short
leads. If a single conductor transmission line is used connect the lamps between
terminal 18 and the screw on the top cover which holds the clamp for the
coaxial transmission line. Disconnect the antenna transmission lines and
harmonic shunts from the output terminals.
Figure 1 in conjunction with the apparatus list shows the correct position
for all tubes and fuses. With this equipment in place, the tuning procedure
is as follows:
Operation of Amplifier into an Artificial Antenna
1. Connect the transmission line clip or clips on output inductance L5
midway between the center tap and the coil ends. Use the left clip
(looking from the front) if a single wire transmission line is used or
both clips if a two wire transmission line is used.
2. Close all doors, apply power to the 50 watt transmitter and adjust the
output for 50 watts as described in the instruction bulletin for that unit.

3. Adjust the "Amp. Grid Tuning" control and the "Neutralizing Capa-
citor" for maximum power amplifier grid current or for maximum
brilliancy of the green lamps which are located underneath the power
amplifier tubes.
4. Turn on the "Plate Supply" switch (D2), the "Power Supply" switch
(D1), and turn the "Amp. Plate Tuning" control thru its range.
Notice where maximum power output is obtained and compress or
spread the turns of the output inductance (L5) so that this point
occurs when the plates of the tuning condenser (C3) are between
one-quarter and one-half meshed. If the circuit tends to tune when
the plates of the condenser are completely meshed compress the turns
of the inductance. If the condenser plates are out, spread the turns.
5. Connect the three adjustable leads to the taps (terminal 2-6) on the
primary windings of transformer T1, using the same numbered tap of
each winding, so that the plate voltage is as close as possible to 2500
volts.
6. Adjust the "Amp. Plate Tuning" control and the position of the clip
on inductance L5 so that the following operating conditions are ful-
filled: (a) The artificial antenna lamps should light to full brilliancy
when compared to a similar lamp lighted from a 120 volt supply.
(b) The plate current should be approximately 0.9 amperes for 30 me
operation, 1.0 ampere for 42 me or a proportional value of current for
intermediate frequencies. (c) The output transmission line current of
the amplifier should increase between 18 and 22 per cent when the
associated transmitter is modulated with a tone sufficiently to increase
the transmission line current of that unit 22 per cent. (d) The amplifier
should provide no power output when the crystal of the 50 watt trans-
mitter is removed and both equipments are turned on.
The procedure for obtaining these results takes the following form:
Adjust the "Amp. Plate Tuning" control until the lamps are lighted
to full brilliancy and notice the plate current. If this current is below
the value prescribed in "b" (above), move the clip or clips on inductance
L5 toward the ends of the coil (or vice versa). During these adjust-
ments keep the 50 watt transmitter adjusted for 50 watts output, and
the "Amp. Grid Tuning" control for maximum brilliancy of the green
lamps (R3.1 and R3.2). If the correct power output and plate current
cannot be obtained readjust the neutralizing capacitor a small amount
at a time until the requirements are fulfilled. Modulate the trans-
mitter with a single tone as described in "c". If an audio oscillator is
not available for this test, modulate the transmitter with voice making
sure that the transmission line current of the transmitter and amplifier
increase in approximately the same proportion. Finally check re-
quirement "d" to see that the set is properly neutralized and that the
crystal has control of the carrier frequency.
[12]

Operation of Amplifier into Antenna Transmission Line
Disconnect the artificial antenna and connect the antenna transmission
line. Follow the procedure as described in adjustment 6 except that instead
of requirement "a" the various controls should be adjusted so that a maximum
of antenna transmission line current is obtained which will also fulfill the other
operating conditions.
When a two-wire transmission line is used the two clips on the output
inductance should be adjusted so that the same transmission line current is
obtained in each line.
The transmission line current meters serve only as an indication that the
equipment is functioning properly. The value of current cannot be used to
determine power into the antenna transmission line because the meters are
not accurate at ultra-high frequencies and the current at the meter is of a
different value from that in the transmission line due to a standing wave which
exists on the connecting wire.
The power amplifier grid current meter is used only in the tuning pro-
cedure for initially adjusting the grid input circuit. Under normal operating
conditions the grid current varies with different amplifier tubes and with
their age.
[ 13 ]

MAINTENANCE
Inspection
The air filter practically eliminates the difficulty of cleaning the equipment
inside the amplifier. However, if it is not operated for long periods of time
some dust may settle in the equipment, and should be removed with high
pressure dry air. The air filter should be cleaned regularly with a warm solution
of soap and water. To remove the filter it is necessary to remove the rear
panel which is held in place by two knurled screws.
As far as possible anticipate tube failures and make the required tube
replacements. Tube failures may be guarded against to some extent by keeping
a record of the length of time the tubes have been in use and of the various
meter readings.
Occasionally check and tighten all connections, nuts, screws and bolts.
Cases of trouble can often be prevented by such tests.
The fan motor should be oiled once a month with not more than two to
four drops of high quality machine oil such as Western Electric KS-2245 oil,
Gulf Security Oil A, Sinclair Commodore Oil, Texaco Regal Oil B; or an equiv-
alent. Too much oil may cause failure of the starting mechanism with sub-
sequent burn-out of the motor.
Relays
The relays in this amplifier have been carefully adjusted before the equip-
ment was shipped. They are of rugged construction and should need little
attention other than the occasional inspection and cleaning of the contacts
with C. P. carbon tetrachloride.
Should one of the relay springs become accidentally bent the defect may
be remedied by the careful use of a pair of long nose pliers. Visual inspection,
coupled with a thorough knowledge of the functions of the relays, should be
sufficient to enable a skilled maintenance man to readjust them after minor
damages.
Relay S1 is a heavy duty plate supply contactor. It has no adjustments
and should require no servicing.
Relay S2 completes the circuit of the filter condenser Cl. This relay is
adjusted by bending the contact arms so that the contacts make at the same
instant and also make before the armature has traveled its full distance. This
distance traveled by the armature after the contacts have just made measured
between the end of the armature and the pole face should be between 142 inch
and %6 inch.
Relay S3 is an overload relay. Its purpose is to turn off the equipment
when the plate current exceeds a safe value. The two contact arms should be
bent so that the contacts break at the same instant. The knurled screw at the
bottom of the relay should be adjusted so that the relay will just not operate
under normal operating conditions when the set is started. This adjustment
[ 14

can be checked by turning the screw clockwise until the amplifier cannot be
turned on, and then turned counter-clockwise two turns. When making this
test it is important that the amplifier be properly tuned as described under
"Tuning Procedure".
Relay S4 is part of the protection circuit. Its function is to operate relay
S2 when condenser Cl is fully charged. There are no adjustments on this
relay and the only service it should ever require is the occasional cleaning of
the contacts with CP carbon tetrachloride.
LOCATION OF TROUBLE
CAUTION: Be sure that high voltage is off before measuring any voltages
or touching anything within the amplifier.
Every effort has been made in the design of this equipment to simplify
the circuits so that possibilities of trouble are reduced to a minimum. The
most important factor in the successful location of trouble is a thorough under-
standing of the functions of the various pieces of apparatus in the amplifier
and in the associated transmitter. When difficulties arise which cannot be
solved by the suggestions mentioned in this chapter the circuits should be
tested with an ohmmeter and references should be made to the schematic and
wiring diagrams in this bulletin and those in the bulletin for the associated
radio transmitter.
Failure to Start
If the 50-watt radio transmitter does not operate when the necessary
switches of that unit are turned on, check the doors of both equipments to see
that they are securely closed. If the 50-watt transmitter operates normally
but the amplifier does not operate when the control switches (D1 and D2) are
closed, test the fuses (F1.1, F1.2 and F1.3) for continuity and notice if the
power supply relay (S1) operates when both equipments are turned on. If
this relay does not operate the difficulty probably is in the control circuits of
the 50-watt radio transmitter or amplifier. If this relay operates, measure the
voltage of each phase of the 220-volt supply and check the circuits to the various
pieces of apparatus associated to this circuit until the defective part is found.
If the amplifier turns on but both units immediately turn off due to ex-
cessive plate current operating the overload relay (S3), check the adjustment of
the grid tuning, neutralizing and amplifier-plate tuning controls as described
under "Tuning Procedure". Check to see that relays S2 and S4 in the protec-
tion circuit operate as described under "Description of Circuits".
Low Plate Voltage
If the plate voltage is low, notice the color of the rectifier tubes (V3, V4
and V5) by observing them through the glass window in the rear panel. If one
tube does not glow or has a whitish color, replace it with a new one. Remove
[15]

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and check the fuses (F1.1, F1.2 and F1.3) with an ohmmeter. If the trouble
persists, turn off the plate supply and measure the filament voltage of the
rectifier tubes. This voltage should be between the limits 2.4 and 2.6 volts a-c.
Low RF Power Output
If the output power is low and the 50-watt transmitter is operating nor-
mally as indicated by the meter readings, check the tuning of the amplifier and
replace each of the amplifier tubes (V1 and V2) with a new one. Measure the
filamentvoltage and the grid bias voltage applied to these tubes. The filament
voltage should be between the limits 10 to 10.6 volts a-c. and the grid bias
voltage measured between each grid terminal (bottom terminal of tube) and
ground should be -200 volts d-c. If the difficulty continues, check the opera-
tion of the transmitter into an artificial antenna as described under "Tuning
Procedure".
Failure to Modulate Properly
If the 50-watt transmitter modulates up as shown by an increase in the
transmission line current of that unit but the antenna transmission line current
does not increase in the same proportion, check the adjustment of the radio-
frequency circuits, replace the amplifier tubes with new ones, measure the
filament and grid bias voltage of the output tubes (V1 and V2) (described in
the previous paragraph), and inspect relay S2 of the protection circuit to make
sure that it operates as described under "Description of Circuits".
Poor quality with normal meter readings of the amplifier and equal per-
centage increases of the transmitter transmission line current and amplifier
antenna transmission line current, probably indicates a difficulty in the 50-watt
transmitter (see instruction bulletin for that unit).
[16]

Circuit
Symbol
APPARATUS LIST
Circuit Use
Cl Plate Voltage Filter
Condensers
C2 Grid Coupling Condenser
C3 Plate Tuning Condenser
C4 Neutralizing Condenser
C5 Filament By-Pass Condenser
C6 Filament By-Pass Condenser
C7 Grid By-Pass Condenser
C8 Plate By-Pass Condenser
C9 Transmission Line Blocking
Condenser
C10 Transmission Line Blocking
Condenser
C11 Load Resistor By-Pass
Condenser
C12 Grid Coupling Condenser
C13 Grid Coupling Condenser
C14 Grid Coupling Condenser
C15 Voltmeter By-Pass Condenser
D1 3 Phase Power Supply Switch
D2 Plate Supply Switch
D3.2
D3.1
D3.3 Door Switches
D3.4
D3.5
F1.1
Fi.2}
F1.3 Power Supply Fuses
Ordering Information
3 Western Electric No. 279A Con-
densers 2 mf. each, 3000 volts.
Western Electric No. D-96889 Con-
denser 50 mmf.
Cardwell No. S-3862 Variable Air
Condenser.
Cardwell No. S-3853 Variable Air
Condenser
Duhilier Type 9 No. 12050 Con-
denser, 0.005 mf.
Dubilier Type 9 No. 12050 Con-
denser, 0.005 mf.
Dubilier Type 9 No. 12010 Con-
denser, 0.001 mf.
Dubilier No. PL-246-6 Condenser,
0.001 mf.
Duhilier No. PL-246-6 Condenser,
0.001 mf.
Dubilier No. PL-246-6 Condenser,
0.001 mf.
Dubilier Type 9 No. 12010 Con-
denser 0.001 mf.
Western Electric No. D-96889 Con-
denser, 50 mmf.
Western Electric No. D-96889 Con-
denser, 50 mmf.
Western Electric No. D-96889 Con-
denser, 50 mmf.
Dubilier No. 3W-12060 Condenser,
0.006 mf.
H & H Switch, Cat. No. 80104
H & H Switch, Cat. No. 3989
H & H Door Switches No. 3592
*25 Amp. 250 Volt Cartridge Fuses
*Not furnished as part of Amplifier, must be ordered separately.
[17]

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APPARATUS LIST (Cont'd.)
Circuit
Symbol Circuit Use Ordering Information
Ll Grid Coupling Coil Coil Assembly per Detail 9A, ESO-
605470, Issue 4
L2 Grid Tuning Inductance Same as Ll
L3 Grid RF Choke Coil Coil Assembly per Detail 23A, ESO-
604301, Issue 6
L4 Grid RF Choke Coil Same as L3
L5 Plate Tuning Inductance**
L6 Plate Voltage Filter Coil
L7 Plate RF Choke Coil
M1 Grid Current Meter
30 31.5 MC 6 turns, coil per
drawing ESO-606573, det. 4-A
31.5 35 MC 5 turns, coil per
drawing ESO-606573, det. 3-A
35- 38.8 MC 4 turns, coil per
drawing ESO-606573, det. 2-A
38.8--42 MC 3 turns, coil per
drawing ESO-606573, det. 1-A
Western Electric No. D-96783 Re-
tardation Coil
Coil per detail 9A, ESO-606573,
Issue 3
Weston Model 301 D.C. Milliam-
meter, Zero Center- -flush type
bakelite case -100-0-100 ma. for
60 degrees C. ambient temperature
M2 Transmission Line Current *Weston Model 425 RF Ammeter,
Ammeter flush type, bakelite case, 0-3 amps.
or 0-5A* for operation at 60 de-
grees C. ambient temperature
M3 Plate Voltage Voltmeter Weston Model 301 DC Voltmeter,
flush type, bakelite case, 0-3000
volts, for operation at 60 degrees
C. ambient temperature
M4 Transmission Line Current *Weston Model 425 RF Ammeter,
Ammeter flush type, bakelite case, 0-3 amps.
or 0-5A for operation at 60 degrees
C. ambient temperature
M5 Plate Current Ammeter Weston Model 301 DC Ammeter,
flush type, bakelite case, 0-2 amps.
for 60 degrees C. ambient tem-
perature
R1 Condenser Charging Current 2-Ward-Leonard Type D 81A inch
Limiting Resistors Resistors, each 10,000 ohms+10
per cent with No. 754 Mounting,
connected in series
*When ordering specify type of transmission line used
0-3 amp. meter for open wire transmission lines
0-5 amp. meter for coaxial transmission lines
**When ordering specify frequency at which amplifier is to operate.
[ 18 1

APPARATUS LIST (Cont'd.)
Circuit
Symbol Circuit Use Ordering Information
R2 Voltmeter Multiplier Type 4, No. 1 Multiplier supplied
with Meter M3
R3.1í
R3.2J Grid Circuit Load Resistors **25 Watt 250 Volt Mazda Lamps,
Green Glass
R4 Power Amplifier Filament Ward-Leonard 2 inch Type O Re-
Resistor sistor, 2.75 ohms
S1 Plate Voltage Supply Relay Ward-Leonard Magnetic Switch,
Cat. No. 10-A3 per K-40509
S2 Rectifier Protection Relay Ward-Leonard Type B, 1 Pole nor-
mally open relay. Cat. No. 81104
with insulating bar
S3 Overload Relay Signal Engineering Co. Relay No.
B2-Z1
S4 Rectifier Protection Relay Ward-Leonard Midget Type Relay.
Cat. No. 106-521
T1 3 Phase Plate Supply Western Electric No. D-96781
Transformer Transformer
T2 Rectifier Filament Western Electric No. D-96782 Trans-
Transformer former
T3 Amplifier Filament Western Electric No. D-96172 Trans-
Transformer former
Vil Amplifier Tubes **Western Electric No. 251A Vacuum
V21 Tubes
V3V4 Rectifier Tubes **Western Electric No. 249B Vacuum
V5 Tubes
M 0 Air Blower "Propellair" exhaust fan, multi-
propeller, horizontal Mounting,
Cat. No. 701, 200 V. AC, 60 cycles
HS1 2nd Harmonic Shunt *Shunt per detail 1A, drawing E SO-
607076
Air Filter Filter per detail 2A, ESO-604704,
Issue 2
*For 2 wire transmission lines an additional 2nd harmonic suppressor should be or-
dered.
**Not furnished as part of Amplifier, must be ordered separately.
1-K-35-wECo-T1266
The apparatus described in this Bulletin
was designed and developed for the
Western Electric Company
by
BELL TELEPHONE LABORATORIES
Printed in U.S.A.
[ 19 1
Instruction Bulletin No. 746
'

1. _A.l. _J - __i.
Akron
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Providence
Reading
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Rochester
St. Louis
A NATIONAL ELECTRIC SERVICE
NEW
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DISTRIItt`T//I{ FI/R C I)ANADA AN F1I'N1LA\U
St. Paul
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Tacoma
Tampa
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Washington
Wichita
Winston Salem
Worcester
Youngstown
Northern Electric Company
LIMITED
General Offices and Plant: 1261 Shearer Street, Montreal, P. Q.
Halifax
Saint John, N. B.
Quebec
Montreal
Ottawa
Toronto
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London
Branch IlouaeaWindsor
New I.iskeard
Sudbury
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FOREIGN DISTRIBUTORS
Regina
Calgary
Edmonton
Vancouver
Victoria
lrrtemal`lofra1StandardElectric Corpotatlon
67 J3road Street New York. U. S. A.
Associated. Allied or Affiliated
ARGENTINA
Cia Standard Electric Argentina,
Casilla de Correo 49 (Street Address,
Defensa 143), Buenos Aires
AUSTRALIA
Standard Telephones and Cables
(Australasia) Ltd., 71 York Street
(P. 0. Box 525-B),Sydney, N. S. W.
AUSTRIA
United Telephone and Telegraph
Works, Ltd., DresdnerStrasse No.75,
Vienna, XX/2
BELGIIIM
Bell Telephone Manufacturing Co.,
4 Rue Boudewyns. P. 0. Box 526,
Antwerp
BRAZIL
International Standard Electric
Corp., Caixa Postal 430 (Street
Address, Aveniebe Rio Rranro,
997101), Rio de Janeiro
CHINA
China Electric Co., I.td., 960
Fokien Road, (P. 0. Box 289),
Shanghai
CZECHOSLOVAKIA
Standard Electric Doms a Spolecnost,
Samova, U 1, 664, Prague
DENMARK
Standard Electric A/S., Gylden-
lovesgade 1, Copenhagen, V.
EGYPT
Standard Telephones and Cables,
Ltd., (7ozzika Buildings, Sharia
Soliman Pasha, Cairo
GERMANY
Standard Elektrizität, Gesellschaft
A/G., Genest Strasse 5,
Itcrlln-Schoneberg
GREAT BRITAIN
Standard Telephones and t'ables,
Ltd., Connaught House, 63 Aldwych,
London, W. C. 2
IIOLLANI)
Bell Telephone Manufacturing Co.,
Scheldestraat 160-162, The Hague
HUNGARY
Standard Electric Co., Ltd.,
l'Jpest 4, n. Budapest
INDIA
Standard Telephones and t'ables,
Ltd., 4, Esplande East (P. 0.
Box 413), Calcutta
ITALY
Standard Elettrica Italiana, Via
Vittoria Colonna No. 9, Milan, 125
JAPAN
Nippon Electric Co., Ltd., 2 Mita
Shikokumachi, Shiba-Ku, Tokyo
JAVABell Telephone Manufacturing Co.,
Bureau in Nederlandsch Oost Indie
Riouwstraat, 85, Itandoeng
DISTRIBUTOR FOR FRANCE AND FRENCH
CompaniesNEW ZEALAND
Standard Telephones & Cables
(Australasia) Ltd., 24-26 Ballance
Street, P. D. Box 638, Wellington
NORWAY
Standard Electric Aktieselskap,
Hovind, Ostre Akre, Oslo
POLAND
Standard Electric Co. W. Polsce,
Sp. Z.0.0. Wspolna 53, Warsaw
PORTUGAL
Standard Electrica,
Restauradores 47-1, S.A. Praca Dos
Lisbon
RUMANIA
Standard Electric Romana, S. A.
37 Calea Victoria', Bucurestl
SOUTH AFRICA
Standard Telephones and Cables,
Ltd., Locarno House, Loveday Street,
(P. 0. Box 1571), Johannesburg
SPAIN
Standard Electrica,
Ramirez de Prado
Box 7040),
S/A., Calle
(Post Office
Madrid
SWITZERLAND
Bell Telephone Manufacturing Co.,
10 Bubenbergplatz, Berne
COLONIES:
Le Materiel Telephoniaue, 413-17 Quai de Boulogne, Boulogne, Billancourt (Seine) France