Philco 811PA Service Manual

PHILCO
TRANSITONE
SERVICE
B
ROADCAST
;lf
i*
f
i
JULY.
I936
POLICE
AUTO RADIO
_
MODELS
8IIPA,
SIIPB AND.SIIPV
There are two new types of Philco potice auto
radio
Receiv-ers, each
<lesigned
to
meet
the
special requirernents
of this,particularly
^rigorous
sen'ice:
The
-Model 8rrPV, a
variable
iuning
Potice Receiver
-
and'the
Mddel
gllp,
a
crystal
controlled, ffxed
frequencv
Receiver,
the Deluxe
Police
Auto
Radio.
"
Both are
single
unit
Receivers, housed in
containers,
l0al
inches
long by
7sl
inches
wide
by
5-15/16
inches
deep.
The
chassis,
housing and
covers
are
all
steel
and are plated to
prevent
rusting.
TheSr
are given an exterior black wrinkle
finish.
Hanger brackets riveted to the
Receiver,
hook
on
to a
dash bracket v'hich
is
per-
CONDENSER
MOUNTING
responsible,
in a
large
measure,
for the
greatly
improved
performnnee
o{ this
Receiver.
HOUSING,
PLATING,
FINISH
MOUNTING
BRACKETS
CONDENSER
DRIVE
CONTROL
U
NIT
TU
BE
EQUIPMENT
The
tubes used
in
the 8llP
and SllPV
are:
f'.
'j
manently installed in
the car, while a
single
bolt at
the
bottom
fastens
the
Receiver secnrely
to
the dash. This
makes
the
installation and removal of the
Receiver
a
sirnple, rapid
operation.
CONTROL
The
volume
control and (in
case
of
Sf
fpv)
llf.il!__ _. _
the tuning control
couplers, the
,.A"
battery
CONNECTIONS
a.rcl.
the
antenna connectors are located
on
one end
of
the housing.
The shafts are
the rapid
coupling
type
with the
locl<ing gland
nut at
the
Receiver
end.
The
"A" battery and
antenna
connections
are quick
detachable
bayonet
locking type, u'ith the
('.A" fuse
placed
in
the
.,A,'
lead.
The tuning
condenser
is
mounted
on
lir.e
rubber.
This prevents microphonic trouble
frorn
developing
in
the
condenser
and
is a
patented
Philco
feature.
78
Tube
-
Tuned
R. F.
Amplifier with A. V.
C.
6AZ Tube
-
First
Detector
-
Oscillator with
A.
V.
C.
78
Tube
-
I. F.
Amplifier
75
Tube
-
Second Detector and
(.Q,
Relay
Stage.
75
Tube
-
First A. F.
Amptifier
with ,,e"
Control.
41 Tube
-
Power Output
Stage
84
Tube
-
Full
Wave
Rectifler.
ANTENN,AS
Both
Receivers employ
antenna
circuits
that
will
track satisfactorily
on any
antenna
capacity
between
100 and 2b00
mmf.
This perrnits satisfactory
operation
on
inserted nretal
top, door,
spare wheel and
other
special types
of
antennas.
A.
V.
C.
Both the R. F.
stage and the
first
detector
stage have
full
automatic volume
control
supplied
by
the
diode
detector.
"Q" CIRCUIT ln
addition to
this, the
Receivers also
have
a
,.e"
or carrier
relay
circuit.
The function
of this circuit is to
completely silence
the
Receiver
when
tuned off
carrier,
or
when the carrier
goes
ofi
the
air.
The
correct
values
of
the
resistor network
have been
deternrined
and
used
for
satisfactory citv
operation where
it is
desirable
to
exclude street car
noises,
etc. A
switch
is
provided on
tl-re
end
of the
Receiver housing, to,open or
close
this
circuit,
since, when
in
remote
sections
of the territory,
where
the
police transmitter
signal might
be
very
weak, slight
additional
sensitivity
can be obtained with
the
.(qr circuit cut out.
This
"Q" circuit
shourd
not be
confused
with the
conventional
squelch
circuit,
relay
circuit
operates on a
carrier
field
strength equivalent
to
approximately 3
rnicrovolts
in
the antenna.
A
carrier
below
this
strength is
almost
always
of
insufficient strength
to
give satisfactory
reception, especially
in
noisy
locations.
DYNAMIC A
full-powered
electro-dynamic speaker
is
:l!45.ER..._.^
used
to
p;ive
clarity of
reproduction
and
SPECIAL
AUDIo better articulation. The audio
and
the
speaker circuits are
especially designed
to
give
the
best
re_
production of the voice
frequencies. The
Receiver
and
spe.Lker
are
capable
of
delivering
considerably greater
undis_
torted output than is
normally
required.
POWER
SUPPLY 'Ihe
pol.ver supply
is
self
contained and
is
not
polarized. The Receiver can
be
stalled
in any car without
reversing
battery
connectior,
Philco's Improved Full-wave
Vibrator is
used.
The
condenser
drive gear ratio
(Model
8I1PV) is 16:1.
This
eliminates
practically
all
back lash and
due
to
the
rnechanism used, prevents
the
tuninE
condenser
from
detuning frorn vibration. This
high
gear
rertio also
rnakes accurate
tuning
much
easier.
The control unit for the
Model
SllPV
is
for
installation on the
edge
of
the
instru-
ment
board.
It
contains
the
"On-Ofl"
switch
and
the
volume
and tuning control knobs.
The calibrated
scale
is illuminated.
The
Model
8llP,
lixed
frequency
Receiver,
utilizes
a
single
control
knob,
which is
mounted
on the
instrument
board.
This
controls the "On-Off"
switch and the
volurne.
SUPERHETERO-
A
superheterodyne
circuit
is
used
for
the
9YryE_.l4N9l
8llPv,
atso
the 811p. The
frequency
8
l
I PV
DRIFT
coverage
of
the Model
8llpV is
frorn
1560
K.C.
to
2600 K.C.
continuously
in
one
band.
The
oscillator
and
I.F.
circuits are
especially
designed
to
reduce frequency
drift to a
minimurn.
RANGE
I I
I
P The Model
811P,
the flxed
frequencSr Re-
ceiver, can be
furnished adjusted
for
any
one
particular
frequency within
the
lirnits of
the regular
police
band,
i.
e.,
from
1630
K.
C.
to
1?12
K.
C.
and from
2B82
K.
C.
to
2490
K.
C.
CRYSTAL
A crystal
controlled oscillator circuit
is
CONTROL
employed
in
the
Model
8tIP.
The
crystal
control holds the oscillator on
the required
frequency
and
is
'1
),1
These models
are without peer and are the
best nrodern
police
Receivers obtainable.
They
represent
the
best
designing,
engineering and production skill in
the
industry.