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, U100, performs four basic functions: 1st
i-f conversion, 2nd i-f limiting, fm demodulation, and
squelch control. The 1st i-f signal (53.55MHz for mid-
band and vhf or 73.35MHz for uhf) enters U100 at pin
10 and passes through an internal preamplifier. The
output of the preamplifier passes out of U100 (pin 9),
through external matching components L1 and C46,
and back into U100 (pin 12) to one input of the 2nd i-f
mixer.
The second injection signal from synthesizer U300
(pin 32) is fed to the other input of the 2nd i-f mixer
(U100, pin 11). The desired output frequency from the
mixer (U100, pin 8) is 450kHz. Therefore, the 2nd
oscillator frequency must be 450kHz above or below
53.55MHz or 73.35MHz; that is, 54MHz or 73.8MHz
(high-side injection), or 53.1MHz or 72.9MHz (low-side
injection).
The resulting 450kHz 2nd i-f signal leaves U100
(pin 8), is filtered by ceramic filters FL3 (between pins
8 and 6), and FL2 (between pins 4 and 3) to reject
unwanted mixer output products.  There is an internal
i-f amplifier stage between the two filters. Next, the
2nd i-f signal is processed through a limiter and
applied to the PLL demodulator. Resistor R3 sets the
free-run frequency of the demodulator to 450kHz;
capacitor C2 is the PLL low-pass filter capacitor.
The output of the demodulator is then fed, via
external dc blocking capacitor C3 (between pins 34
and 32), to an internal amplifier stage. The audio out-
put signal from this stage leaves U100 (pin 31) and is
fed, via dc blocking capacitor C14, to pins 8 and 9 of
the audio filter IC, U101.
U100 also includes squelch controller circuitry that
functions as follows: From the audio amplifier output
the noise and audio are sent, via external shaping net-
work R4, R5, C12, and C13, and an internal noise lim-
iter (U100, pins 27 and 26), to the programmable
squelch attenuator in U101 (pin 17). The output of this
attenuator (U101, pin 19) is fed to the squelch con-
troller circuit in U100 (pin 23).
The output voltage of this rectifier circuit is
inversely proportional to the noise level present; there-
fore, it is directly proportional to the rf signal strength.
When the noise level exceeds the threshold level set
by the squelch attenuator in U101 (pin 19), the
squelch controllers output (U100, pin 18) goes low,indicating the absence of a carrier signal. The micro-
computer IC, U400, reads this SQUELCH signal (pin
15) and programs the audio filter IC, U101, to pull the
AUDIO PA ENABLE line (U101, pin 3) low, turning off
the audio power amplifier in U102. The opposite con-
dition (low noise level) will pull the AUDIO PA
ENABLE line high, allowing the audio to be processed.
(3) Receive Audio (U101, U102)
At the audio filter IC, U101 (pins 8 and 9), the
recovered audio from U100 is low-pass filtered to sep-
arate squelch codes and high-pass filtered to separate
voice. Squelch codes are filtered, sampled, and sent
(U101, pin 28), via the PL DECODE line, to the micro-
computer, U400 (pin 41). If the radio is in the PL/DPL
squelch mode, U400 turns on its decoding circuitry.
When the squelch signals are decoded, U400 sends
program signals to a microprocessor interface circuit
in U101. Then, U101, via the AUDIO PA ENABLE line,
turns on the audio PA IC, U102.
After high-pass filtering, voice audio is de-empha-
sized, filtered, sent through a programmable attenua-
tor. Finally, the voice audio passes from U101 (pin 24),
through a low-pass filter (C47, R19) to the audio PA
(U102, pin 10).
Inside U102, the voice audio is applied simultane-
ously to three amplifiers: the internal PA, the external
PA, and the common PA. The common PA is for both
internal and external speaker applications in a bridge
configuration. Without an external speaker connected,
a high input at pin 24 of U102 (SPEAKER SELECT
line) biases the internal PA, and audio from the inter-
nal and common PAs is 180° out of phase, which
drives the internal speaker differentially. Audio from
the common amplifier to the external amplifier is in
phase.
If an external speaker is connected to the radios
universal connector, the SPEAKER SELECT line
(U102, pin 24) is pulled low. This low-biases the exter-
nal PA, and shifts the audio of the common amplifier
180°. This phase shift does two things: First, it puts
the audio output from the common amplifier 180° out
of phase with the audio output from the external ampli-
fier, and the external speaker is driven differentially.
Second, audio from the common amplifier and the
internal amplifier is in phase, resulting in no audio
drive for the internal speaker.
h. Transmitting
(1) Transmit Audio (U102, U101, U700)
Pressing the PTT switch (S803) applies a ground
to pin 60 of microcomputer U400, activating the repro-
gramming of the chip set. First, the audio filter IC
(U101) is reprogrammed to mute the radio and set up
the normal transmit path functions without changing
12 
						

							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.
Initially, an audio signal enters the enabled micro-
phone and the audio is routed to the audio preamplifi-
er, U102 (pin 21 for internal microphone; pin 22 for
external microphone), where some necessary shaping
and filtering is done. Next, the output (pin 11) of U102
is fed through capacitor C23, and resistors R17 and
R18 (part of the pre-emphasis/limiter circuit) to pins 11
and 10 of audio filter U101.
Within U101, the TX filtering is enabled for flat
audio or pre-emphasis, and PL/DPL encode is set.
From the output of the limiter, the signal then goes
through the splatter filter to the summer, where the
microphone input is summed with the AUX TX input
and the PL/DPL encode signal. The PL tones are gen-
erated by U101, using the PL sample clock signal
(U400, pin 39) as a reference. This clock signal is a
square wave multiple of the desired PL frequency. The
summer output then goes through a buffer into two
attenuators. 
A five-bit attenuator adjusts the VCO modulation
level, then sends the signal (VCO MOD) from U101,
pin 21, to pin 3 of synthesizer/VCO module U300. The
four-bit attenuator adjusts the reference modulation
level, then sends the signal (REF MOD) from U101,
pin 20, to U300, pin 19.
(2) Transmit RF (U202)
The frequency-modulated, on-channel signal from
U300 (pin 14) is fed to pin 1 of the rf power amplifier
(PA), U202. The level of this input is nominally +5dBm.
The mid-band PA is a 3-stage amplifier with
adjustable gain in the 1.0- to 6.0-watt range. The vhf
PA is a 3-stage amplifier, with adjustable gain in either
the 1.0- to 2.5-watt range or the 2.0- to 6.0-watt range,
depending on the radio model. The uhf PA is a 4-stage
amplifier, with adjustable gain in either the 1.0- to 2.0-
watt range or the 2.0- to 5.0-watt range, depending on
the radio model. All rf power amplifiers have nominal
input and output impedances of 50½.
In the mid-band PA, the second-stage collector
(U202, pin 6) is used to control PA gain. The third-
stage base bias network (U202, pin 7) is also connect-
ed to pin 6, providing a variable base bias to maximize
efficiency at lower power levels. The third-stage col-
lector (pin 12) is tied directly to battery (unswitched)B+. The first-stage collector (pin 3) is tied to bias
switching transistor, Q204, which is turned on only in
transmit by the transmit automatic level control IC,
U201. A TX 5V regulator in U201 supplies +5V to pin
16 (U201) only during transmit. A switch within U201
causes pin 17 to go low (0V), saturating Q204; R209
is for current limiting. When the radio is not transmit-
ting, the TX 5V is low (0V) and pin 17 is pulled up to
approximately +7.5V, which turns off Q204.
In the vhf PA, the first-stage collector (U202, pin 3)
is used to control PA gain. The second- and third-
stage collectors are tied directly to battery
(unswitched) B+ (pins 6 and 12). A switching transis-
tor, Q204, supplies base bias to pin 7. When the TX
5V regulator in transmit automatic level control IC,
U201, turns on, +5V is supplied to U201, pin 16. A
switch within U201 causes U201, pin 17, to go low
(0V), saturating Q204; R209 is a current limiting resis-
tor. When the TX 5V regulator is low (0V), U201, pin
17, pulls up to approximately +7.5V and Q204 is
turned off.
In the uhf PA, the first-stage collector (U202, pin 2)
is supplied by Q200, which is connected to the TX 5V
regulator (U201, pin 16) in an emitter follower configu-
ration. When the TX 5V regulator is on, regulated
+4.3V is supplied to U202, pin 2; when the TX 5V reg-
ulator is off, Q200 is cut off and no current passes.
The second-stage collector voltage (U202, pin 3) is
used to control the gain of the uhf PA. The third- and
fourth-stage collectors (U202, pins 6 and 8) are tied to
battery B+. Base bias is supplied to U202, pin 4, via
switching transistor Q204 (PNP Darlington). The base
of Q204 is tied to pin 26 of U201 through current-limit-
ing resistor R209. When the radio is receiving (TX 5V
regulator off), U201, pin 26, is pulled up to +7.5V, turn-
ing off Q204. When the TX 5V regulator is on, the volt-
age at U201, pin 26 drops to approximately +4.5V, sat-
urating Q204.
In all radiosthe gain control voltage for U202, pin
3, is supplied by U201 via pass transistor Q202. The
PA control circuit inside U201 sets the control voltage
to establish the correct ratio between the RF DET volt-
age from the FDS module, U203 (pin 5 mid-band and
vhf; pin 4 uhf), and the D/A reference voltage from
U200, pin 9. This reference voltage is software con-
trolled and depends on the current channels pro-
grammed power level.
In high-power model PA modules, an internal ther-
mistor is connected between ground and U202 (pin 11
on mid-band and vhf; pin 9 on uhf). Resistor R210
connects the thermistor to the TX 5V regulator, form-
ing a voltage divider. The resulting temperature sense
voltage is fed to pin 8 of U201. Circuitry within U201
causes the PA power to cut back (via the control volt-
age supplied to U202, pin 3) if the PA temperature
exceeds a preset value. The cutback temperature is
determined by the value of R210.
13 
						

							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 microcomputer, giving
the radio expanded channel capability, and
·control of the DTMF generator, U505.
The COPE microcomputer communicates with the
radio board over the DATA and BUSY lines. Both lines
are wired-or; that is, any processor can force the lines
to a logic low state (0 volts), but not to a logic high (+5
volts). This is accomplished by using a 10k½pull-up
resistor on each line. These resistors are located on
the radio board and are connected to #2 regulated B+.
When the COPE (or any other processor) sends a
low over the DATA or BUSY line, it forces the line to
the low state by sinking current through the lines out-
put pin. To send a high, the processor switches the
output pin to the high impedance state (open), and the
pull-up resistor causes the line to go high (as long as
no other processor is forcing it low). Normally the
DATA and BUSY lines will be in the high state.
Bus messages are indicated by 9600-baud data on
the DATA line, accompanied by a logic low on the
BUSY line. A constant low on either line indicates aproblem that could be either hardware or incorrect pro-
gramming of one of the microcomputers. To prevent
degradation of receiver performance, inductors L501
and L503, and capacitor C507 filter out computer
hash interference from the DATA and BUSY lines.
The COPE gets its +5V power (#2 regulated 5V
from the radio board) through pin 28. Inductor L504
and capacitor C501 provide filtering. The COPEs
RESET line, pin 17, is connected to the radio boards
RESET line via filter L502 and pin 5 of the LCD inter-
connect flex. Whenever the RESET line goes low,
then high again, the COPE reinitializes itself, briefly
turning on all segments of the display.
Components Y502, C505, C506, and R528 are the
external elements of the microcomputer clock circuit.
The resulting 3.6864 MHz oscillator signal is divided by
four inside the COPE, and becomes the internal clock.
Pins 30 through 40 are control lines for the EEP-
ROM, U501. These lines are normally at a logic high
level unless the COPE is accessing data from the
EEPROM. None of these lines should ever be at a
constant low level.
Pin 32 is a power strobe for EEPROM U501;
power strobing is used to reduce current drain. The
strobe signal controls the regulator circuit, which con-
sists of Q501, Q502, Q504, R503, and C502. When
pin 32 is high, the switched B+ on the emitter of Q502
is regulated down to +5V and applied to pin 16 (Vdd)
of EEPROM U501. When pin 32 is low, the voltage on
U501, pin 16, is reduced to 0V. Normally, pin 32 will be
low; it goes high only when data is being accessed
from the EEPROM. On power-up, a series of power
pulses, lasting as long as a second or more, are sent
from pin 32 as the COPE reads and validates data in
the EEPROM.
14
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							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 kilobaud.
Pin 31 is the control line for the LCD backlight.
Two yellow-green LEDs, CR501 and CR502, make up
the backlight. These LEDs are driven by a constant-
current source consisting of dual-diode CR503, resis-
tors R501 and R504, and transistor Q503. The current
through the LEDs (about 20 mA) is drawn from the
switched B+ supply. The current remains constant for
battery voltages greater than six volts.
Pins 2 and 3 are the MODB and MODA inputs.
These pins are tied high and low through R512 and
R513, respectively; they determine the mode that the
microcomputer will be in after it is reset. MODB must
be high and MODA must be low for the COPE to oper-
ate properly.
Pin 27 is an open drain output control line for mut-
ing the microphone during DTMF sequences. Resistor
R527 is a pull-up resistor to +5V. Transistor Q506
completes the bias current path for the microphone,
which is located on the speaker/microphone flex.
When pin 27 is high (.7V), Q506 is biased on and the
microphone is live; when pin 27 is low (0V), Q506 is
off and no microphone signal is produced. The actual
voltage at pin 27 can never go above .7V (one diode
drop).
Pins 33 and 34 form another serial bus. The
COPE uses this bus to send serial clock and data
information to the LCD driver IC, U504, and, on the 8k
board only, to DTMF generator IC U505. The bus is
synchronous; that is, one of the lines (pin 33) is used
to clock the data on the other line (pin 34). Resistor
R506 provides some isolation on the data line. During
data transfer, the receiving ICs acknowledge data by
putting a low on the data line. The COPE cannot tri-
state pin 34 or read the acknowledge; therefore, R506
limits the current that flows if the output from pin 34 is
high.
Pins 46 through 53 are keypad input lines. These
are high impedance lines and need to be pulled high
by resistors R517 through R524. The keypad lines are
normally all high unless a key is pressed. Each key
causes exactly two of the lines to go low (row and col-
umn). The COPE decodes the lines and processes the
keypress.
Pin 36 is a high-impedance logic input that is con-
nected, via the LCD interconnect flex (pin 8), to the
fast squelch line on the main board (U100, pin 21).
The fast squelch signal is used by the COPE during
scanning to detect the presence of carrier.
j.  EEPROM IC (U501)
Depending on the display circuit board, U501 is
either a 2k or an 8k EEPROM IC. Besides the data
and address lines already discussed in the COPE
microcomputer section, U501 has four control lines,
which are all active low; that is, a low on the pin acti-
vates the associated function.
(1) The CC (chip clear) line (pin 17) is an unused
input that is normally used to erase the entire
memory. The CC pin is tied high to the Vdd pin
(16), always inhibiting this function. The CC func-
tion is not present on the 2k EEPROM.
(2) The CE (chip enable) line (pin 7) is used to enable
the EEPROM for either read or write.
(3) The WE (write-enable) line (pin 15) is used with
the CE line to write to the EEPROM. Resistor
R502 ensures that the WE line is held inactive
during power-up and power-down so that inadver-
tent writes are avoided.
(4) The OE (output enable) line (pin 11) is used with
the CE line to read from the EEPROM. The OE
signal causes the data I/O pins (2 through 6, 30
through 32) to become outputs.
k.  LCD Driver IC (U504)
The LCD driver IC, U504, interfaces with the
COPE microcomputer via a 2-wire synchronous bus
(pins 30 and 31). The COPE sends LCD display data
over the bus to the LCD driver. The driver does not
require refreshing; that is, once the data has been
sent to the driver, the driver will maintain the display
without further service from the COPE. Only when the
display requires changing does the COPE again com-
municate with the driver.
The LCD driver has its own internal clock, con-
trolled by resistor R516, which determines the frame
frequency of the driver waveforms. Pin 41 (VLCD) is
used to set the driver output level, which affects the
contrast, viewing angle, and segment crosstalk of the
display. Resistors R507 and R511 set the voltage level
at pin 41 to about .5V, the optimum level for the type of
LCD being used. The lower the dc voltage on VLCD,
the greater the driver output level.
The LCD driver outputs two types of waveforms to
the LCD: backplane and segment. The three back-
plane waveforms, output from pins 42 through 44, are
shown in the applicable service manual. These signals
resemble staircase waveforms, and are displaced
apart in phase from each other by 120 degrees. Four
discrete voltage levels are used: 0.5, 2.0, 3.5, and 5.0
volts; voltages that differ much from these values indi-
cate a problem. The frequency of the backplane wave-
forms should be close to 50 Hz.
The other type of waveform, the segment driver
waveform, is sent to the LCD via pins 1 through 29,
and 45 through 56 (a total of 40 segment waveforms).
15 
						

							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 seen.
The display driver is initialized at power-up with all
segments and annunciators turned on. However, cer-
tain annunciators may have been disabled through
programming; these annunciators will not be 
displayed.
l.  DTMF Generator IC (U505) 
(8k circuit boards only)
The dual-tone multi-frequency (DTMF) generator
IC, U505, generates DTMF tone pairs for transmission
over the air. The DTMF generator IC interfaces (pins
20 and 23) with the COPE over the same serial bus as
the LCD driver IC. To send a message to the correct
destination, the COPE includes the bus address of the
desired IC as part of the communications protocol.
When it is not being used, the DTMF generator is
in the quiescent state and draws very little current.
The COPE sends a message on the bus to awakenthe DTMF generator, causing the generator to start its
3.579545 MHz crystal oscillator, Y501. The DTMF
generator listens for messages, which turn tone pairs
on or off. These tone pairs are sent from pin 15
through resistor R526 to the main radio board.
Resistor R526 is part of a voltage divider that
attenuates the .9-volt peak-to-peak signal (by about 30
dB) to a level that is in the same range as the micro-
phone output level. The other resistor in the divider is
R9 on the main radio board. R526 also serves to iso-
late the DTMF generator from the microphone circuit
when transmitting voice. C503 filters out high-frequen-
cy clock noise that might corrupt the DTMF signal.
The DTMF signal shares the same line as the
microphone on the front shield. During DTMF
sequences, the COPE mutes the microphone by inter-
rupting its bias current via Q506.
m. SECURENET Module (U900)
(SECURENET radios only)
The SECURENET module, U900, uses pins 4, 5,
7, and 16 for keyloading. If the encryption key is lost or
destroyed, the module will indicate this by sending a
logic low level from pin 16 whenever the radio’s PTT
switch is pressed and, periodically, when the radio is
not transmitting or receiving.
When the radio is transmitting, the SECURENET
module is put into the appropriate mode (coded or
clear) by its microcomputer, which gets this information
16 
						

							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 material out
and away from the inside of the radio.
Alcohol is a high-wetting liquid and can carry con-
tamination into unwanted places if an excessive quan-
tity is used. Make sure that controls or tunable compo-
nents are not soaked with the liquid. Do not use high-
pressure air to hasten the drying process, since this
could cause the liquid to puddle and collect in unwant-
ed places.
Upon completion of the cleaning process, use a
soft, absorbent, lintless cloth to dry the area. Do not
brush or apply any isopropyl alcohol to the frame, con-
trol top, front cover, or back cover.
3. DISASSEMBLY AND REASSEMBLY
For disassembly and reassembly of the radio,
refer to the DISASSEMBLY/REASSEMBLY PROCE-
DURES, exploded views, and exploded view parts
lists in the applicable service manual.
Several special tools are required to disassemble
the radio completely. Refer to the Specialized Tools
and Test Equipment and the Torque Specifications
charts in the applicable service manual.
NOTE
SABER radio contains complementary metal-oxide
semiconductor (CMOS) devices, which are highly
susceptible to damage in handling due to static dis-
charge. The entire printed circuit board should be
treated as static sensitive. Damage can be latent,
resulting in failures occurring weeks or months
later.
DO NOT attempt to disassemble the radio without
first referring to the Safe Handling of CMOS
Devices paragraph in this section of the manual.
4. SAFE HANDLING OF CMOS DEVICES
Complementary metal-oxide semiconductor
(CMOS) devices are used in the SABER radio. While
the attributes of CMOS are many, their characteristics
make them susceptible to damage by electrostatic or
high voltage charges. Damage can be latent, resulting 1. INTRODUCTION
This section of the manual describes recommend-
ed repair procedures, special precautions regarding
maintenance, and recommended test equipment.
Each of these topics provides information vital to the
successful operation and maintenance of the SABER
radio.
2. PREVENTIVE MAINTENANCE
The SABER radio does not require a scheduled
preventive maintenance program; however, periodic
visual inspection and cleaning is recommended.
a. Inspection
Check that the external surfaces of the radio are
clean, and all external controls and switches are func-
tional. A detailed inspection of the interior electronic
circuitry is not needed or desired.
b. Cleaning
The following procedures describe the recom-
mended cleaning agents and the methods to be used
when cleaning the external and internal surfaces of
the radio. External surfaces include the front cover,
housing assembly, and battery case. These surfaces
should be cleaned whenever a periodic visual inspec-
tion reveals the presence of smudges, grease, and/or
grime. Internal surfaces should be cleaned only when
the radio is disassembled for servicing or repair.
The only recommended agent for cleaning the
external radio surfaces is a 0.5% solution of a mild
dishwashing detergent in water (one teaspoon of
detergent per gallon of water). Stronger cleaning
agents may be used only to remove soldering flux
from circuit boards after making repairs.
(1) Cleaning External Surfaces
The detergent-water solution should be applied
sparingly with a stiff, non-metallic, short-bristled brush
to work all loose dirt away from the radio. A soft,
absorbent, lintless cloth or tissue should be used to
CAUTION
The effects of certain chemicals and their vapors
can have harmful results on certain plastics.
Aerosol sprays, tuner cleaners and other chemi-
cals should be avoided.
Neverallow any alcohol- or solvent-based prod-
MAINTENANCE
17 
						

							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 that are used for storage or trans-
portation of other semiconductor devices.
b. All CMOS devices must be placed on a grounded
bench surface and the technicians must ground
themselves before handling the devices. This is
done most effectively by having the technician
wear a conductive wrist strap in series with a 100-
kilohm resistor to ground.
c. Do not wear nylon clothing while handling CMOS
circuits.
d.
Do not insert or remove CMOS devices with power
applied. Check all power supplies to be used for
testing CMOS devices, and be certain that there
are no voltage transients present.
e. When straightening CMOS device leads, provide
ground straps for the apparatus used.
f. When soldering, use a grounded soldering iron.
g. All power must be turned off in a system before
printed circuit boards containing CMOS devices
are inserted, removed, or soldered.
5. REPAIR PROCEDURES AND TECHNIQUES
a. Parts Replacement and Substitution
Special care should be taken to be as certain as
possible that a suspected component is actually the
one at fault. This special care will eliminate unneces-
sary unsoldering and removal of parts, which could
CAUTION
Leadless component technology requires the
use of specialized equipment and procedures for
repair and servicing of the SABER radio.  If you
are not totally familiar with leadless component
repair techniques, it is strongly recommended
that you either defer maintenance to qualified
service personnel and service shops or take the
recommended video taped leadless component
repair training program, MAV-PACK 3 (VID-952)
(see paragraph 6b, Service Aids and
Recommended Tools, in this section).  This is
very important since irreparable damage to the
radio can result from service by unauthorized
persons.  Unauthorized attempts to remove or
repair parts may void any existing warranties or
extended performance agreements with the
damage or weaken other components or the printed
circuit board itself.
When damaged parts are replaced, identical parts
should be used. If the identical replacement compo-
nent is not locally available, check the parts list for the
proper Motorola part number and order the compo-
nent from the nearest Motorola Communications Parts
office listed in the Replacement Parts Ordering sec-
tion of this manual.
b. Rigid Circuit Boards
The SABER radio uses bonded multi-layer printed
circuit boards. Since the inner layers are not accessi-
ble, some special considerations are required 
when
soldering and unsoldering components. The printed
through holes may interconnect multiple layers of the
printed circuit. Therefore, care should be exercised to
avoid pulling the plated circuit out of the hole.
When soldering near the module socket pins, use
care to avoid accidentally getting solder in the socket.
Also, be careful not to form solder bridges between
the module socket pins. Closely examine your work
for shorts due to solder bridges.
c. Flexible Circuits
The flexible circuits are made from a different
material than the rigid boards, and different tech-
niques must be used when soldering. Excessive pro-
longed heat on the flexible circuit can damage the
material. Avoid excessive heat and excessive bend-
ing. For parts replacement, use the (Motorola part
number) 0180382A38 Temperature-Controlled Solder
Station with a 600 or 700 degree tip, and use small
diameter solder such as (Motorola part number)
1010041A60. The smaller size solder will melt faster
and require less heat being applied to the circuit.
To replace a component on a flexible circuit, grasp
the edge of the flexible circuit with seizers near the
part to be removed, and pull gently. Apply the tip of
the soldering iron to the component connections while
pulling with the seizers. Do not attempt to puddle out
components. Prolonged application of heat may dam-
age the flexible circuit.
6. TEST EQUIPMENT AND SERVICE AIDS
The following paragraphs describe the test equip-
ment and service aids required for maintaining the
SABER radio. Your Motorola sales representative will
assist in analyzing your specific requirements and
help you select the latest available equipment to suit
your individual needs. In addition, your sales repre-
sentative can advise you of the availability of new test
equipment and service aids that become available
after the printing of this manual.
Refer to Figure 4 for an illustration of the trou-
bleshooting, programming, and test equipment setup.
18 
						

							19
Figure 4.  Troubleshooting, Programming, and Test Equipment Setup Detail
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?@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@hf?@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@hf?@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ W2@6X?fW&eW26Xe?W&?@@@@f@@6X@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@hf?@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 7
						

							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 item or no substitution is recommended.
b. Service Aids and Recommended Tools
Refer to the appropriate vhf or uhf service manual
(SERVICE AIDS and RECOMMENDED TOOL
LIST) for a listing and description of the service aids
and tools designed specifically for servicing the
SABER radio, and the more common tools required to
disassemble and properly maintain the radio. These
kits and/or parts are available from the Motorola
Communications Parts office listed in the
Replacement Parts Ordering section of this manual.
(1) MAV-PACK
The Motorola Video Visual Package (MAV-PACK)
20is a VHS videotape in standard half-inch format. The
following MAV-PACKs, and others, are available from:
Motorola C&E, Inc.
National Service Training Center
1300 N. Plum Grove Road
Schaumburg, Illinois 60195.
(a) MAV-PACK 3 (VID-307)
This training video introduces the SABER radio, its
unique service aids, theory of operation, programming
techniques, and present troubleshooting procedures.
(b) MAV-PACK 3 (VID-952)
This MAV-PACK is a video tape training program
on leadless component repair techniques and is
strongly recommended for technicians who intend to
service this and other Motorola radios using leadless
components. This VHS format video cassette and sup-
plemental literature describe the removal and replace-
ment of leadless components using the following spe-
cialized equipment:
• RRX-4033 Laurier Hot Gas Bonder
• RPX-4234A Regulator and Hardware Kit 
						

							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 and the procedures necessary
to place it back in operation in the shortest possible
time.
The radio service manual, schematic diagrams,
and troubleshooting procedures provide valuable
information for troubleshooting purposes. The service
manual provides signal flow information in a simplified
format, while the schematic diagrams provide the
detailed circuitry and the biasing voltages required for
isolating malfunctioning components. By using the
diagrams, troubleshooting procedures, and deductive
reasoning processes, the suspected circuit may be
readily found.
To determine if analysis of the radio is required,
perform checks such as 12dB SINAD and rated audio
performance for the receiver, and current drain, fre-
quency error, and deviation for the transmitter. These
should give the technician a general indication of the
problems location.
After the general problem area of the radio has
been identified, careful use of a dc voltmeter, rf milli-
voltmeter, and an oscilloscope should isolate the prob-
lem to an individual component.
2. PRELIMINARY CHECKS
When a radio performs unsatisfactorily, the follow-
ing procedures should help localize the fault.
a. Check Battery
The first step in localizing a trouble is to ensure
that the battery is fully charged; ideally, verify the
operation of the radio on a battery eliminator. Follow
the troubleshooting procedures in this manual, and
the appropriate service manual.
b. Alignment
Strict adherence to the published procedures is a
prerequisite to accurate alignment and proper evalua-
tion of the performance of the radio. The selection of
test equipment is critical. The use of equipment other
than that recommended should be cleared through
your Motorola Area Representative to ensure that it is
of equivalent quality.
The service technician must observe good servic-
ing techniques. The use of interconnecting cables that
TROUBLESHOOTING
21 are too long, poorly positioned (dressed), or improper-
ly terminated will result in erratic meter readings, 
making it impossible to tune the radio to the desired
specifications.
Use the recommended test equipment setup and
proper connections for alignment and adjustments.
Refer to the detailed procedures supplied in the appli-
cable service manual.
c. Check Overall Transmitter Operation
If the battery voltage is sufficient, check the overall
performance of the transmitter. A good overall check
of the transmitter is the rf power output measurement.
This check indicates the proper operation of the trans-
mitter amplifier stages. A properly tuned and operating
transmitter will produce the rated rf output into a 50-
ohm load with a dc input of 7.5 volts. If the rf power
measured is less than rated rf output, refer to the
applicable transmitter troubleshooting procedure.
d. Check Overall Receiver Operation
(1) 12dB SINAD
This procedure is a standard method for evaluat-
ing the performance of an FM receiver, since it pro-
vides a check of the rf, i-f, and audio stages. The
method consists of finding the lowest modulated sig-
nal necessary to produce 50% of the radios rated
audio output with a 12dB or better ratio of signal +
noise + distortion / noise + distortion. This is termed
usable sensitivity.
To perform this measurement, connect the leads
from a SINAD meter to the audio output of the test
box. Set the Motorola service monitor or rf signal gen-
erator to output a 1-millivolt signal. Modulate the rf sig-
nal with a 1kHz tone at 3kHz deviation. Introduce the
signal to the radio at the exact channel frequency
through the universal connector. Set the volume con-
trol for rated audio output (3.74Vrms). Decrease the rf
signal level until the SINAD meter reads 12dB.  The
signal generator output (12dB SINAD measurement)
should be less than 0.35µV on mid-band and vhf
receivers or less than 0.35µV on uhf receivers. If the
radio does not meet this specification, refer to the
receiver troubleshooting procedure.
3.
VOLTAGE MEASUREMENT AND SIGNAL TRACING
To aid in troubleshooting, ac and dc voltage read-
ings are provided (in red) on the main circuit board,
and 2k and 8k display circuit boards schematic dia-
CAUTION
When checking a transistor or module, either in
or out of the circuit, do not use an ohmmeter hav-
ing more than 1.5 volts dc appearing across the
test leads or an ohms scale of less than x 100.