Zenith J584W - Page 18

16
SECTION FOUR
THEORY AND APPLICATIONS
FIGURE 1 - MODEL JR587W
INTRODUCTION
"J Line" chassis can be divided into three basic catagories
1. Continued chassis designs.
2. Modified chassis designs.
3. New chassis designs.
Table A provides a ready comparison between the various
"J Line" chassis, as well as a comparison with corresponding
"H Line" chassis. Chassis 3WJR51 is the only design concept
that is continued without change from the "H Line".
RF/IF/MPX circuitry of Chassis 1WJR55, 3WJR50 and
3WJR52 is basically the same. However, the mechanical
layout of each chassis and their physical locations in the
cabinet are significantly different. Some of these differences
will be illustrated as we proceed through this service manual.
In order to facilitate understanding, explanations will be in
the following subject groups:
1. Chassis 3WJR50, 50Z and 3WJR52, 52Z RF/IF/MPX/
Audio. Discussions of Chassis 3WJR52 will also apply to
the Chassis 3WJR50 Series, except as noted.
2. Chassis 1WJR55 Audio. The greatest number of tech 
nological advances incorporated in a new "J Line" chassis
includes design concepts introduced in the "J Line"
"Mini Wedge" plus an audio output IC not previously
used in any of our Stereo Audio Products.
3. Chassis 8WJR56, 8WJR57 and 15WJR29. New Magnetic
Phono Preamp, and increased power output.
4. Chassis 8WJR56 and 8WJR57. Audio circuitry includes
Hi Cut and Lo Cut Switches.
5. Models J587W, JR587W and JR588W. Disassembly
procedures.
6. Models J596W and JR596W. Disassembly procedures.
7. Other modular models, disassembly procedures.
CHASSIS 3WJR52
In the "G Line", "Wedge" Modular models G596W and
GR596W (using Chassis 12WGR59) were introduced. These
were followed by their "H Line" counterparts, Chassis
12WHR29, used in Modular Models H596W and HR596W, as
well as in Console Model HR966P. Those two chassis incor 
porated several state of the art concepts making a first appear 
ance in a Zenith Stereo Audio Product and those concepts will
be continued in "J Line" Models J596W, JR596W and JR966P.
Among new concepts that were introduced in "G and H Line"
"Wedge" chassis were the following:
1. Separate RF and IF circuits for AM and FM.
2. Separately mounted AM Oscillator Trimmer.
3. Ceramic Filters in the FM IF.
4. Integrated Circuit IF Gain Block.
5. Integrated Circuit IF Limiter and Quadrature Detector.
6. Integrated Circuit Phase Locked Loop (PLL) Multiplex
Detector.