Chevrolet 985203 Manual

CUSTOM SERIES 95 TRUCK RADIO 985203
This radio has four tubes and two hi-gain tran-
sistors and is designed for the Series 95 trucks.
The radio consists of a radio receiver unit with
•• t •• • ~
',\ I
:I
I' 14 of
Figure
82
an external speaker. This type of design is ad-
vantageous for both installation and service as
all component parts of the receiver are readily
accessible for nuick efficient replacement when
service is required. Using an external type
speaker affords the advantage of having a larger
type speaker in a limited space area. The speak-
er is coupled to the instrument panel by a special
'.'
Figure 83
89
type gasket, thereby using the entire instrument
panel for unusually good tone reproduction.
ELECTRICAL DESCRIPTION
The circuit ' used in this receiver is ' the super-
heterodyne type that uses no regeneration. The
tuning circuits are of the permeability type and
are tuned by varying the iron cores in and out of
the antenna, radio frequency and qscillatot. coils
like pistons. The 'interm'ediate frequency stages
are tuned by means of two iron cores in each
transformer and are adjusted with an insulated
screw driver from the bottom and top of each
transformer; both the first (input) and second
(output) interItlediate frequence transformers are
tuned by this method. See Figure 83.
The antenna circuit Is capacity 'coupled to the
antenna by means of an adjustable antenna trim-
mer condenser to' take care of normal variations
in antenna and antenna coil capacity. The antenna
condenser is adjustable by means of a small
screw driver and is located at the lower front on
the right side of the radio ' case.
The automatic volume control is of the delayed
signal type and is very capable of main~aining a
constant level of volume at all times. Very high
frequency filter chokes are used in the radio
frequency grid circuit to discriminate against
ignition interference In the receiver, thus elim-
inating the use of spark plug and distributor
suppressors.
TUBE AND TRANSISTOR COMPLEMENT
12DZ6
12AD6
12EK6
12AE6A
DS26
DS503
AND FUNCTION '
Radio frequency amplifier
Oscillator - modulator
Intermediate frequency amplifier
Detector - Automatic volume control
and first audio
Audio ' driver transistor
Audio output "HI-POWER" transistor
GENERAL INFORMATION
Tuning range 540 - 1615 kilocycles
Intermediate frequency - 262 kilqcycles
Maximum power output 4.2 watts
Undlstorted power output 3.2 watts
Current drain 1.4 amperes at 12 volts
Speaker-Alnico V permanent magnet type 6 x 9
, Inch
Voice coil impedance 4 ohms at 400 cycles
All cl!:cuits ,!se a printed circuit board