Motorola Saber Theory Maintenance 68p81044c05 O Manual

loss of about 6 to 7dB through the mixer, the i-f ampli-
fier provides about 10B of gain, and the crystal filter
has about 3.5dB insertion loss. The crystal filter sup-
plies some 40dB of attenuation at the adjacent chan-
nel and 80dB of attenuation at the second image. The
bandwidth of the i-f signal leaving U2 (pin 1) is typical-
ly 14 to 18kHz, centered on 73.35MHz, with a typical
gain of 5.5 to 8.5dB. The first i-f signal now moves into
the i-f IC, U100.
(2) 2nd I-F and Squelch (U100)
The i-f IC,...

the status of the R/T line (1 = RX; 0 = TX).
Depending on the status of the MIC SELECT line
(0Vdc = external; 5Vdc = internal), either the external
or internal microphone will be enabled. With an exter-
nal microphone, the voltage level on the OPT SEL line
from the external microphone (universal connector pin
7) will reflect the type of microphone being used
(1.235V = remote speaker/microphone; 2.5V = public
safety microphone). The microphone will not actually
be enabled until the TX 5V is active....

i.  COPE Microcomputer (U502)
Refer to Figure 3 and the 2k and 8k schematic
diagrams in the applicable service manual.
The control of peripheral electronics (COPE)
microcomputer is the heart of the display board. The
COPE has several functions, the main ones being:
·control of the liquid crystal display, which displays
information about the state of the radio,
·processing of information input by the user via the
radios keypad,
·communication of channel information (stored in
the EEPROM) to the CORE...

Pins 9 through 16 make up a bidirectional data bus
between the COPE and the EEPROM. These lines are
normally at a logic low unless data is being accessed.
Pins 41 through 45 are output lines from the
COPE, and form the lower five bits of the EEPROM
address. The upper eight EEPROM address bits (six
bits for a 2k board) come from U503, an 8-bit serial-to-
parallel shift register. These address bits are sent from
the COPE over the serial peripheral interface (SPI)
bus (pins 22, 25, and 26) at 57.6...

Each segment waveform drives three display seg-
ments ( the small lines or bars that make up the indi-
vidual characters), or annunciator symbols (such as
the battery symbol). The actual appearance of the
segment waveforms depends on the data being dis-
played. Generally, the segment waveforms will contain
the same voltage levels as the backplane waveforms
discussed above; however, a segment waveform may
contain only two of the four levels (0.5V and 5.0V 
or
2.0V and 3.5V). All four levels also may be...

remove the solution and dry the radio. Make sure that
no water remains entrapped near the connectors,
cracks, or crevices.
(2) Cleaning Internal Circuit Boards 
and Components
NOTE
Always use a fresh supply of alcohol and a clean
container to prevent contamination by dissolved
material (from previous usage).
Isopropyl alcohol may be applied with a stiff, non-
metallic, short-bristled brush to dislodge embedded or
caked materials located in hard-to-reach areas. The
brush stroke should direct the dislodged...

in failures occurring weeks or months later.
Therefore, special precautions must be taken to pre-
vent device damage during disassembly, troubleshoot-
ing, and repair. The following handling precautions are
mandatory for CMOS circuits, and are especially
important in low humidity conditions.
a. All CMOS devices must be stored or transported in
conductive material so that all exposed leads are
shorted together. CMOS devices must not be
inserted into conventional plastic snow or plastic
trays of the type...

19
Figure 4.  Troubleshooting, Programming, and Test Equipment Setup Detail
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a. Recommended Test Equipment
The list of equipment contained in Table 2 includes
all the standard test equipment required for servicing
two-way portable radios, and several unique items
designed specifically for servicing the SABER radio.
Battery-operated test equipment is recommended when
available. The CHARACTERISTICS column is includ-
ed so that equivalent equipment may be substituted;
however, when no information is provided in this col-
umn, the specific Motorola model listed is either a
unique...

1. INTRODUCTION
Servicing the SABER Series radio requires the
localization of the malfunctioning circuit before the
defective component can be isolated and replaced.
Since localizing and isolating a defective component
constitutes the most time consuming part of trou-
bleshooting, a thorough understanding of the circuits
involved will aid the technician in performing efficient
servicing. Technicians must know how one function
affects another; they must be familiar with the overall
operation of the radio...