Espey Mfg. Co., Inc. 7B-12 Schematic

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Manufacturer:Espey Mfg. Co., Inc.

Schematics Content:

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This Receiver features the latest in A. M. f F. M.,
Receiver Design. Eleven (11) tubes plus a Rectifier are
used in the A, M. g F. M. superheterodyne Circuit.
separate antennas are supplied for A. M. and F. M. An
automatic frequency control tube is used to stabilize the
F. M. and simplify tuning.


l Type (iBAG ~~ F. M. R F. Amplifier

l Type 7FS - F. M. Converter

1 Type 7Q7 f A. M. Converter

1 Type 6C4 f~- Automatic Frequency Control

l Type 7AH7 >~ l. F. Amplifier

l Type oSH7 - Detector Driver (PM)

l Type (SSQ7 ~~ lst Audio Amplifier, A. M. Detector
l Type 7A6 f" Ratio Detccfor

l Type 7F7 ~~ 2nd Audio Amplifier and phase inverter
2 Type 7C5 -ff Beam power output.

l Type 5Y3/GT W' Rectifier.


1) The "ON'OFF" power switch and Tone Control
is the knob at the extreme left of the set. Turn this conf
trol in a clockwise direction until the switch clicks and thc
dial becomes illuminated. Turning this control further in
the same direction will change the tone.

the left.

will increase the volume.

3) The Band Switch is the third knob from the
left. The extreme counterclockwise position of this knob
is for phonograph operation. The center position is for
FM reception. The extreme clockwise position is for

The Volume Control is the second knob from
Turning this control in a clockwise direction

4) The Tuning Control is the extreme right hand
knob. Turning this knob in either direction will move

the dial pointer and select the stations on the A. M. or

In most cases it will not be necessary to use external
antennas. since the receiver is equipped with a loop anI
tenna for AM reception and an indoor type folded dipole
antenna for FM reception.

When inadequate reception is obtained from a desired
station, it may`be necessary to reposition the antennas to

' meter

favor that station. On AM, the loop should be turned so
that the edge faces toward the station desired. On FM,
the entire cabinet should be positioned so that the back
is hroadside to the direction from which the signals are

For the reception of weak or distant stations, or for
the operation of the receiver in unfavorable locations,
provisions are made for the use of external antennas.
The folded dipole should be disconnected when an e>tV
tcrnal FM antenna is employed.

Do not disconnect the AM loop when an external
antenna is used on standard broadcast.

Futlitre of the Reccibcv to opertlle may be doe to.

l) All tubes not firmly in sockets
Z No current at power socket.

3) Band Switch in wrong position.
4) Speaker not plugged in.

5) Antennas not attached.

6) Defective fuse in Receiver,

Equipment Required:
l. Set band switch to AM, advance volume control to
full volume setting

Broadcast Band Signal Generator,
Output Meter.

2 Connect output inctcr across Voice coil

3. Conncct the Signal Generator across thc broadcast
band antenna (Rear) section of the variable condenserv
The "high" side of the Generator should connect to the
Stator section and the "ground" side to the chassis.
Adjust the Signal Generator to 453 kc and with the
receiver switched on, adjust the first and second l. F>
transformers for peak output as shown on the output
The signal injected into the receiver should be as
small in magnitude as possible. consistent with a useful
deflection on the output meter.

4. Connect the. "high" side of the Generator to thc
antenna terminal with a 200mmf condenser inserted in
series.. Connect the "ground" side of the Generator to
the chassisv Tune receiver to 60 on the dial, adjust Sig'
nal Generator to GOOkc. Adjust the BC antenna coil for
maximum deflection on the output meter,

Use a weak

(C)John F. Rider

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5. Tune receiver to 160 on the dial. Adjust Signal
Generator to 1600kc. Adjust BC oscillator and BC anr
tenna trimmers for maximum output.

6, Repeat operations 4 and 5.

NOTE: Points A, B. C. D. E. F. G. and H are noted on

civcuit diagram. Points C, and D have been
bfought out to the unused contacts of the speaker
socket at the 'rear of the chassis.

Equipment Required:

a) High frequency Signal Generator With 88/108
Mc tuning range.

b) Signal Generator capable of delivering .l Volt

c) Audio output meter.

d) D. C. vacuum tube voltmeter with zero center

c) Tuning wand.

Disable AFC. dining alignment of FM. circuits by
short circuiting point "B" to chassis.

A. Ratio Detector Alignment:

1. Connect V.T.V.M. across point "C" and ground,

2. Feed 10.7mc unmodulated R.F. Signal into 6$H7
grid (point A) through .Ol ufd. condenser. This signal
should be .1 volt.

3. Adjust primary of Ratio Detector (T15) for maxif
mum voltage indication on V. T. V. M.

4. Connect zero centered V. T. V. M. across point
"D" and ground.

5. Adjust secondary of Ratio Detector (TfS) for zero

` 6. Tune 10.7mc Signal Generator higher in frequency
(about ZOOkc) until maximum voltage reading is obtained

on V. T. V. M.; note this voltage, then tune signal genI

opposite polarity is obtained. Note this voltage, then if
necessary re'adjust primary of the Det. (T'S) until the
voltages are about equal on either the high or low side of

(C)John F. Rider

erator lower in frequency until maximum voltage Of thev


1. Shunt a 1,000'ohm carbon resistor across the priml
ary of the detector (TfS) (Points G and H).

2. Connect output meter across speaker voice coil.

3. Volume and tone controls at maximum clockwise

4. Connect 10.7mc (modulated 30%) signal genera'
tor through .Olufd condenser across point "F" and

5. Adjust secondary, then primary of (T13) for maxir
mum audio output. (Reduce input signal to maintain
output at .waatt level.)

6. Connect 10.7mc 30?/o modulated signal generator
across point "E" and ground.

7. Adjust secondary, then primary of (T~1) for maxi'
mum audio output. (Reduce input signal to maintain
output at .Sewatt level.)

8. Remove 1000'ohm shunting resistor from across
primary of (T'S).


1. Connect V. T. V. M. across point "C" and ground,

2. Connect lO8mc signal generator to FM antenna
terminals. If generator impedance is low, put one 150'
ohm carbon resistor in series with each of the generator
leads. Tune receiver dial to 108 mc.

3. Adjust FM oscillator trimmer (C'SI) for maxi'
mum V. T. V. M. reading.

4. Adjust FM Rf. trimmer (Cf52) for maximum
V. T. V. M. reading. During alignment reduce input
signal to maintain Detector voltage at 2.V.

5. Repeat steps 3 and 4.
6. Feed a 90mc signal into antenna terminals (as in
C12), tune receiver dial to signal.

7. Test R. F. coil with tuning wand and if necessary
adjust spacing of FM R.F. coil (L14) for maximum V.T.
V.M. reading at 90mc. During alignment reduce input
signal to maintain Detector voltage at 2.V.

8. Repeat steps 2 and 4 if necessary.
9. Remove A.F.C. shorting jumper.

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