Motorola Saber Theory Maintenance 68p81044c05 O Manual

							grams in the service manual. When making these volt-
age checks, pay particular attention to any notes that
may accompany the voltage reading of a particular
stage.
Replacing a transistor or module before a thorough
check is made is not recommended. Read the volt-
ages around the suspected stage. If these voltages
are
not
close to those specified, the associated components
should be checked.
A low-impedance meter should not be used for
measurement. If all dc voltages are correct, the signal
should be traced through the circuit to show any pos-
sibility of breaks in the signal path.
4. TROUBLESHOOTING PROCEDURES
The troubleshooting procedures on the following
pages will help isolate troubles in the different sections
of the radio. Start at the first step of the appropriate
procedure and make the checks as indicated. Most
usual malfunctions will respond to the systematic
approach to troubleshooting
.
a. Initial Checks
(1) Power-up the radio, then check standby current:
current should be either 65mA (programmed) or
40mA (unprogrammed). If unprogrammed, com-
plete step (8) and check current again.
(2) Check the regulators: No. 1 regulator = 5Vdc (Q1
collector); No. 2 regulator = 5Vdc (U103, pin 8);
receive regulator = 5Vdc (U201, pin 12).
(3) Check that the RESET line (J1, pin 5) = 5Vdc.
(4) Check that the IBP crystal (Y400) frequency =
7.37 MHz; measure at U400, pin 10.
(5) Check for data activity (J4, pin 15) when the radio
is powered-up.
(6) Check for 2.1 MHz at pin 17 of synthesizer mod-
ule (U300).
(7) Check that the R/T line (U201, pin 9) = 5Vdc in
receive mode; 0Vdc in transmit mode.
(8) Always ensure that a known good checksum (test
file) is loaded into the radio. If the radio has cus-
tomer data, save that particular file and load the
test file.
b. Radio Will Not Program
(1) Check that the IBP crystal (Y400) frequency =
7.37 MHz.
CAUTION
The integrated circuits and modules in the radio
are static sensitive devices. DO NOT attempt to
troubleshoot or disassemble the radio without
first referring to the Safe Handling of CMOS
Devices paragraph in the MAINTENANCE
(a) Check the dc levels on both sides of the crys-
tal; these levels are derived from microcom-
puter U400. The levels should be approxi-
mately 2.0Vdc and 2.5Vdc.
(b) 1. If the correct dc levels are present and
there is no 7.37MHz signal, piggyback
another crystal and check for the correct
frequency.
2. If the correct dc levels are not present,
make sure that all dc voltages to U400 are
correct.
(c) Check the continuity of L400 with an ohmmeter.
NOTE
Transistor Q403 is only used to shift the crystal
frequency; this does not affect the operation of
the crystal.
(2) Check the WATCHDOG TIMER DISABLE output
line of the microcomputer (U400, pin 37) for a
5Vdc level. Use an oscilloscope for this check and
be sure that the line is not toggling.
NOTE
Pin 37 of U400 should always indicate 5Vdc;
this indicates proper operation of the micro-
computer. If 
there is a checksum (software) or
hardware error in the microcomputer, this line
will either toggle or remain low.
(a) If the voltage reading is incorrect, attempt to
reprogram the radio:
1. If the radio will not program, go to step b (8).
2. If the radio will still not program, check
that pin 19 of U400 is at a constant 5Vdc
level and is not toggling.
(b) Place a jumper across R405; this disables the
RESET line to the microcomputer. Check
U400, pin 37 again.
1. If the line does not read 5Vdc, suspect
U400.
2. If the line does read 5Vdc, attempt to
reprogram the radio. If the radio will still not
program, check pin 30 of U101 for 4Vdc. If
pin 30 = 4Vdc, then suspect U101.
(3) Check the volume control (R800) voltage range:
(a) Check the voltage range at J2, pin 6, with an
oscilloscope by rotating the volume knob from
minimum to maximum volume. The indication
should be a linear level increase from 0 to 5Vdc.
(b) Repeat step b (3) (a) at pin 56 of U400. If the
volume potentiometer does not show a linear
increase, check the continuity of the PTT/con-
trol flex circuit.
(4) Check the frequency switch (S823) positions:
(a) Take measurements at J2, pins 5, 8, 9 and 10.
Rotate the switch through all channel posi-
tions and verify (with oscilloscope) that each
line has a 0Vdc and a 5Vdc level.
(b) Repeat step b (4) (a) at pins 53, 55, 59, and 22 
						

							61 of U400.
If there are no indications on either step (a) or (b),
check for the presence of 5Vdc on the common
line of the frequency switch.
(5) Verify with an oscilloscope that the BUSY line (J4,
pin 12) is at a constant 5Vdc level.
NOTE
The BUSY line of U400 reads low only when the
DATA lines (pins 22, 27) are active. This is the case
when the radio is first powered up.
(6) (a) Check the microcomputer data output line
(U400, pins 28, 29) conditions with an oscillo-
scope:
·Condition 1 - With the radio in the standby
mode, there should be no data activity.
·Condition 2 - When the volume control,
frequency switch, PTT switch, or monitor
button is actuated, there should be data
activity.
(b) The DATA output lines from U400 control the
microprocessor interface units in U101 (pin
31), U700 (pin 11), and U200 (pin 23), and
channel information to U300 (pin 30). If any of
these devices is defective, it could hold the
DATA line inactive.
1. Check the dc level of each of these
devices.
2. Make sure that the 2.1 MHz signal from
U300 (pin 17) is correct.
3. Make sure that there is data activity at
U400, pin 11, during volume adjustment,
channel changing, and pressing of the
PTT and monitor switches.
(7) Check the voltage references of microcomputer
U400 (pin 63 = 0Vdc and 0½to ground; pin 64 =
5Vdc).
NOTE
These two voltage points on U400 set up an inter-
nal voltage reference table within the microcomput-
er. If the voltages are incorrect, certain functions of
the radio may operate erratically; for example,
monitor, volume, etc.
(8) Check the transmit 5Vdc line (U201, pin 11).
Ensure that there is no dc level with the radio in
the standby mode. If a dc level is present, this
may indicate a microcomputer lockup condition. 
Another lockup condition may be present if all
checks seem normal, but the radio still fails to
communicate with the PC. If this is the case, then
perform steps (a) and (b):
U900 Keyloader
Kit No. Kit No. Description
NTN4711/NTN5832 T3010 DVP
NTN4713/NTN5834 T3014 DVP-XL
NTN4715/NTN5836 T3012 DVI-XL
(a) Turn the radio off and ground pin 3 of J4.
Then, while pressing the PTT switch, turn on
the radio. Remove the ground and release the
PTT switch.
(b) With the radio in this condition, program the
radio. If the radio will not program, go to step
b (2) (a) 2.
c. Radio Will Not Keyload 
(SECURENET radios only)
(1) Verify that the correct keyloader is being used for
the particular type of encryption present in the
radio. Refer to the following chart:
(2) Replace the SECURENET module, U900, with a
test module having the same kit number. If the
problem persists, continue troubleshooting.
(3) (a) Check that U900, pin 9, =5Vdc.
(b) Check that U900, pins 15 and 18, =7.5Vdc.
(c) Verify that activity is present on pins 6 and 11
of U900 when the radio is turned on.
(d) Check that the KEYLOAD line (U900, pin 5)
goes low when the keyloader cable is
attached to the radio’s universal connector. If it
does not go low, suspect a bad cable or an
open between pin 10 of the universal connec-
tor and pin 5 of U900.
(e) Check that the WRITE ENABLE line (U900,
pin 7) momentarily goes low while attempting
to load a key. If it does not go low, suspect an
open between pin 5 of the universal connector
and pin 7 of U900.
(f) Check that there is data applied to the
KEY/FAIL line (U900, pin 16) while attempting
to load a key. If no data is applied, suspect an
open between pin 9 of the universal connector
and pin 16 of U900.
(g) Check that there is data applied to the KEY
INSERT DATA (KID) line (U900, pin 4) while
attempting to load a key. If no data is applied,
suspect an open between pin 11 of the univer-
sal connector and pin 4 of U900.
d. Standby Current
(1) Verify that the radio has a good checksum, and is
squelched. If the standby current is consistently
high (>80 mA), replace the rf PA module, U202. If
the current is still bad, replace the remaining mod-
ules, one at a time, with test modules.
(2) Make a visual check of the main circuit board.
Ensure that all tantalum capacitors are placed cor-
rectly (proper polarity). Check for solder bridges.
(3) Check the transmit 5Vdc line (U201, pin 11).
Ensure that there is no voltage with the radio in
the standby mode.
23 
						

							NOTE
Both number 1 and number 2 regulators must be
operational for the microcomputer (U400) to func-
tion properly.
(4) Check that the voltage at the collector of number 1
regulator Q1 = 5Vdc. If the voltage is lower than
4.8Vdc or higher than 5.2Vdc, then complete this
step:
(a) Check that the resistance of Q1 collector to
ground = approximately 4k½(negative side of
the probe connected to ground).
(b) Check the bias levels of Q1: emitter = 7.5Vdc;
base = 6.7Vdc. If the levels are wrong, sus-
pect the i-f IC, U100.
(5) Check that the voltage at the output (pin 2) of
number 2 regulator U103 = 5Vdc.
NOTE
This regulator rarely fails, so be sure to check for
solder shorts and assembly on the main board.
(a) Check the parameters of U103: the voltage at
pin 8 (input) should be 7.5Vdc; pin 5 should
read 5Vdc (ensure that this line (RESET) is
not toggling).
(b) Check that the resistance from U103, pin 2, to
ground is 4k½.
e. No Transmit Capability
(1) (a) Check that the voltage at pin 60 of microcom-
puter U400 is 0Vdc when the PTT switch is
pressed.
(b) Check that the voltage at pin 60 of U400 is
5Vdc in standby (PTT switch not pressed).
(c) Check that the voltage at U400, pin 62, is
2.5Vdc with the test box connected to the
radio. This line also should be at 0Vdc with
the external PTT switch pressed.
(2) Check to see if the radio unlocks during transmit
(tone). Observe the LOCK DETECT line (U300,
pin 16) with an oscilloscope while keying and
dekeying the radio. The line should remain low,
with no 0-to-5V transition.
(a) First, verify that the channel under test is not
designated a blank transmit channel.
(b) A tone emitted when the PTT switch is
pressed indicates either that the synthesizer is
unlocked, or that the channel information from
U400 is incorrect.
1. Replace the synthesizer with a test syn-
thesizer. If the synthesizer is still unlocking
during transmit, check to see if the code-
plug is correct.
2. Reprogramming of the radio may be
required.
(3) (a) Check the 16.8MHz reference frequency
(U300, pin 1) with a 50½probe and a frequen-
cy counter.(b) Check pin 4 of U301 for 5Vdc; check pin 1 of
U301 for 2Vdc to 4.5Vdc.
(c) Remove synthesizer module U300 and repeat
step e (3) (a).
NOTE
Ensure that the reference oscillator pad is
placed correctly.
(4) (a) The R/T line is a logic line from the micropro-
cessor interface (pin 42) of U101 to the Tx/Rx
switches of U101 (internal), U200 (pin 10),
and U201 (pin 9). Check that the R/T line
goes from 5Vdc to 0Vdc during transmit. 
(b) If the R/T line is not switching, make sure that
there is data activity at pins 11, 28, and 29 of
U400 when the radio is keyed. The clock line
(pin 30) also should be active during PTT.
(5) (a) Check the transmit 5Vdc line (U201, pin 11)
for 5Vdc during transmit. If the voltage is cor-
rect, measure the current drain during trans-
mit; the drain should be ³800mA.
1. If the current drain is Å400mA, the rf PA is
not being enabled; go to step e (6).
(b) (
For vhf radios only). Check pin 17 of U201.
The voltage should be 7.5Vdc with the radio
unkeyed and 0Vdc with the radio keyed. If a
bad reading is obtained, remove U202 and
recheck the voltage.
NOTE
Pin 8 of U201 is the temperature sense control
line only.
(c) Check pin 4 of U201. The voltage should be
7.5Vdc with the radio unkeyed and 6.3Vdc
with the radio keyed. If a bad reading is
obtained, remove U202 and recheck the voltage.
(d) Pins 21 and 25 of U201 set up the current
control levels. These pins should read 2.5Vdc
for proper operation.
(e) Resistor R207 (U201, pin 30) sets up a transmit
current limiting level. This resistor should mea-
sure 14.7k½for mid-band and vhf or 15k½for
uhf.
(6) Check all transmit parameters of rf PA U202:
(a) While keying the radio, either (mid-band and
vhf) check pins 7 and 11 of U202 for 6.5Vdc
and 2.8Vdc respectively, or (uhf) check pins 4
and 9 of U202 for 6.5Vdc and 2.8Vdc respec-
tively.
(b) While keying the radio, check pin 3 of U202
for 2.5 to 6.5Vdc; 6.5Vdc indicates the maxi-
mum power setting.
(c) While keying the radio, check pins 21 and 25
(mid-band and vhf) or pin 25 (uhf) of U201 for
2.5Vdc.
f. No Transmit Power
24 
						

							(1) Perform step e (6) before continuing with this pro-
cedure.
(2) Check the output (pin 14) of synthesizer U300:
(a) While keying the radio, measure, with an rf
millivoltmeter, the synthesizer output where it
enters the rf PA (U202, pin 1). A level of 200
to 500mVac should be measured.
1. (Mid-band only). Check L209 for continuity.
2. (VHF only). Check L210 for continuity.
(b) While keying the radio, measure, using a fre-
quency counter with a 50½probe (use the
guide pin of the rf PA module for ground), the
frequency of the synthesizer output where it
enters the rf PA (U202, pin 1). The carrier fre-
quency should be observed.
1. If the frequency measured is incorrect or
not present, repeat the check using a
spectrum analyzer with U202 removed.
Check for proper drive level (250mV) 
and verify that the signal is clean (no
parasitics).
(3) Verify the power output of the rf PA (U202):
(a) Remove FDS module U203.
(b) Connect a 50½probe with a 30dB pad to a
power meter, and probe pin 13 (mid-band and
vhf) or pin 10 (uhf) of rf PA U202. Make sure
that the probe is grounded (use the ground
side of C204 on mid-band and vhf radios; use
a screw head for ground on uhf radios). 
Do
not
touch pin 13 (mid-band and vhf) or pin 10
(uhf) with your finger during this check.
(c) Key the radio. Six to seven watts should be
measured (high-power PA).
1. If the power level is incorrect, check the V-
control line of (pin 3) U202. With the FDS
module (U203) removed, this line should
go to the maximum level (6.8 to 7.0 Vdc).
(d) Reinstall FDS module U203.
1.
If the voltage level in step f (3) (c) 1 was low,
dekey the radio. short pins 3 and 6 of
U202 together. This will force the rf PA
into maximum gain. Read the power level
again as in step f (3) (c).
(4) Verify the operation of the PA control circuit in U201:
(a) While keying the radio, measure the voltage
on the RF DETECT line at U203, pin 5 (mid-
band and vhf) or pin 4 (uhf). The voltage
should be from 2.5 to 5Vdc.
1. The rf detect line of U203 should change
as the power word is changed. Short pins
3 and 6 of U202 together and verify that
this line goes to approximately 4.0Vdc.
(b) While keying the radio, measure the D/A refer-
ence voltage at U201, pin 7; this voltage setsthe power level of the radio. The reference
voltage should be from 2.5 to 4.5Vdc; 4.5Vdc
is the maximum setting.
1. The reference voltage should change
when the power level word from the field
programmer is changed. If there is no
change, check pin 21 of U200 with an
oscilloscope and verify that this line goes
active when the power word is being
changed.
(c) Verify the operation of the op amps in U201 by
applying the formula, (V x 2) - 4 = Vr. V = the
voltage measured in step f (4) (a); Vr = the
voltage that should have been  measured in
step f (4) (b).
(5) (a) Check the FDS parameters (remote port) by
keying the radio and measuring the voltage
levels at the following pins of U203:
·(
For mid-band and vhf radios). Pin 8  =
6Vdc; pin 9 = 4.5Vdc; pin 12 = 6.5Vdc; pin
13 = 5.0Vdc.
·(
For uhf radios). Pin 7 = 4.7Vdc (transmit)
and 7.4Vdc (receive); pin 8  = 0Vdc; pin
11 = 7.5Vdc.
(b) If any of the voltages measured were incor-
rect, check that U201, pin 23, is set to remote
antenna enable (4.6Vdc). This sets up 
the
biasing to the diodes in FDS module U203 via
the transmit ALC IC, U201, pins 20, 24, 26, and
28 (vhf) or pins 16, 17, and 20 (uhf).
g. No Receive / Poor Receive
(1) Inject 53.55MHz (mid-band and vhf) or 73.35MHz
(uhf) from a frequency generator at or near the
antenna and listen for the presence of a 1kHz
tone. Use the generators HI-LEVEL output @ 0dB
(1kHz modulation, 3kHz deviation). If the tone
(signal) is present, continue with this procedure; if
no tone is heard, go to step g (3).
(2) Check the radios rf section:
(a) Using a frequency counter with a 50½probe,
check the synthesizers input to the 1st LO
(U4, pin 1 for mid-band or pin 3 for vhf; U2,
pin 4 for uhf), using the guide pin of the front
end module (mid-band and vhf) or the front-
end screw head (uhf) for ground. The reading
should indicate 53.55MHz + carrier frequency
(mid-band and vhf) or carrier frequency -
73.35MHz (uhf).
1. If the desired frequency cannot be read,
remove the front end module and check
the input again, using the ground side of
capacitor C51 (mid-band and vhf) or C212
(uhf) for probe ground. If the desired fre-
quency is present, continue with this pro-
cedure (radio in remote):
25 
						

							a.(For uhf radios only). The uhf front
end module (U2) and the RX 5Vdc
regulator (U201) will not function if the
FDS module (U203) is not in place.
Turn the radio off, then back on again,
then do the following:
(1) If the FDS module is in place but
there is still no RX 5Vdc at pin 3
of U2, check the voltages on pin 7
(7.4Vdc), pin 8 (0Vdc), and pin 11
(7.5Vdc) of U203 in remote only.
(2) Another indication would be to
key the radio momentarily, then
check RX 5Vdc. If the voltage is
correct, check Q207 and Q208,
and/or replace the FDS (U203).
b. Check that the 16.8MHz reference
signal is present at pin 1 of U300.
2. If the desired frequency is present, contin-
ue with this procedure (radio in remote).
(b) Using a 50½probe, inject the carrier frequen-
cy at pin 2 of U4 (mid-band and vhf) or pin 9
of U203 (uhf). The signal level should be
approximately 0.68µV (mid-band and vhf) or
0.4µV (uhf) for 12dB SINAD.
If a good reading was obtained, continue with
the next step (mid-band and vhf) or go to step
g (2) (f) (uhf); if the reading was less than
12dB SINAD, go to step g (3).
(c)
(For mid-band radios only).Using a 50½
probe, inject the carrier frequency at pin 1 of rf
amplifier module U1; use pin 11 of U203 for
probe ground. The signal level should be
approximately 0.27µV for 12dB SINAD.
(d)
(For vhf radios only).Using a 50½probe,
inject the carrier frequency at pin 11 of two
pole filter U1; use pin 2 of U203 for probe
ground. The signal level should be approxi-
mately 0.27µV for 12dB SINAD. Check that
the TUNING VOLTAGE level at U1, pin 5, is
0.7Vdc at 146MHz.
(e)
(For vhf radios only).Check the bias voltages
at the rf amplifier, Q3. If these voltages are
incorrect, suspect T1.
(f) Using a 50½probe, inject the carrier frequen-
cy at pin 12 of U203; use pin 11 (mid-band
and vhf) or pin 13 (uhf) of U203 for probe
ground. The signal level should be approxi-
mately 0.27µV for 12dB SINAD.
(g) Check the dc voltages of U203.
(h) Replace the FDS module, U203, and repeat
step g (2) (e).
(3) Using a frequency counter with a 50½probe,
check the synthesizers input (U300, pin 32) to the2nd LO, using the ground side of CR800 for
ground. The reading should indicate 53.1MHz or
54.0MHz (mid-band and vhf), or 72.9MHz or
73.8MHz (uhf).
(4) Using a 50½probe, inject 53.55MHz (mid-band
and vhf) or 73.35MHz (uhf) at inductor L1; place
the positive end of the probe where C46 and L1
connect. Use the ground screw of the front end
module (vhf), the ground pin (pin 5) of U4 (mid-
band), or pin 3 of J2 (uhf) for probe ground. The
signal level should be approximately 90 to 100µV
(mid-band and vhf) or 1.2µV (uhf) for 12dB
SINAD.
(5) Using a 50½probe, inject 450kHz at filter pin 1 of
FL3 (mid-band and vhf) or pin 1 of U2 (uhf). Use
pin 2 of FL3 (mid-band and vhf) or a screw head
(uhf) for probe ground. The signal level should be
approximately 3.5µV for 12dB SINAD. If this step
fails, go to the Receive Audio procedure.
h. Receive Audio
(1) Using a 50½probe, inject 450kHz at filter pin 1 of
FL3 (mid-band and vhf) or pin 1 of U2 (uhf). Use
pin 2 of FL3 (mid-band and vhf) or a screw head
(uhf) for probe ground. Set the input signal level at
-60dBm. Set the radio to rated audio (3.7Vac) and
measure the distortion level. If the distortion level
is greater than 5%, or 3.7 Vac cannot be obtained,
continue with this procedure.
(2) (a) Check the voltages of the i-f IC, U100 (volt-
ages are approximate): pin 8 = 4.5Vdc; pin 9 =
1.5Vdc; pin 10 = 0.9Vdc; and pin 12 = 1.5Vdc.
These voltages determine if the op amps in
the IC are functional. If the voltages are cor-
rect, continue the procedure.
(b) Ensure that the No.1 regulator voltage is not
below 4.8Vdc when set to rated audio.
NOTE
The current drain should be approximately
200mA at rated audio.
(c) Inject 450kHz (-60dBm) at pin 1 of FL3 (mid-
band and vhf) or pin 1 of U2 (uhf). Check the
discriminator output (U100, pin 31) with an
oscilloscope for a symmetrical sine wave.
When no signal is applied, the reading should
be 3.5Vac of noise. If the result is not symmet-
rical or if the signal is low, check resistor R3.
(3) (a) Inject a modulated 1kHz signal (-30dBm) at
capacitor C14. Adjust the radio for rated audio
and measure the distortion level.
(b) Vary the volume level and monitor the audio at
capacitor C22. The signal should not clip
until approximately 4.0Vac.
NOTE
If the audio processing bit has been set or
tuned lower, the audio will clip at a lower level.
26 
						

							This will affect distortion measurements.
(4) (a) Inject a modulated 1kHz signal (-30dBm) at
capacitor C22. Adjust the radio for rated audio
(3.7Vac) and measure the distortion level.
(b) Check pins 4, 28, and 31 of U102 for 6.5Vac
p-p. At maximum volume, the waveform
should be clipped.
i. Receive Coded Audio 
(SECURENET radios only)
(1) Replace U900 with a SECURENET bypass mod-
ule (NTN4720A). Verify that the radio operates
properly in the clear mode.
(2) (a) Replace U900 with a test module. Ensure that
the transmitting and receiving units have the
same encryption key.
(b) Set the service monitor or rf signal generator
to output a 1-millivolt signal. Introduce the sig-
nal to the radio at the exact channel frequency
through the universal connector. Modulate the
rf signal with an encrypted 1kHz tone at 4kHz
deviation. Set the volume control for rated
audio output (3.74Vrms).
(c) Check that a 1kHz tone is present at the
speaker.
(d) Check that an eye pattern is present at U900,
pin 2.
(e) Check that a 1kHz signal is present at U900,
pin 3 and U101, pin 7.
(f) Decrease the rf signal to 1µV. Check that a
1kHz tone is still present at the speaker.
j. Transmit Audio
(1) (a) Inject a 1kHz signal (25 mV) through the uni-
versal connector. Key the radio and observethe service monitor scope for a symmetrical
sine wave. If the signal appears distorted,
replace the synthesizer module, U300, and
retest.
(b) Check pins 21 and 22 of U102 for 3.5Vdc with
the radio keyed. This voltage turns on the
amplifiers in U102.
(2) (a) Using a 50½probe, inject a 1kHz  signal (0.5
to 1.0 Vac) at capacitor C23. Key the radio
and observe the service monitor scope for a
symmetrical sine wave.
(b) Ensure that the signal is reaching pins 10 and
11 of U101; the level at pin 10 will be consid-
erably lower than that at pin 11. Also, ensure
that the signal is reaching pins 15, 16, and 22
of U101.
(3) Inject 1kHz at 1 Vac at R16 (U101 side). Key the
radio and observe the service monitor scope for a
symmetrical sine wave. If the signal appears dis-
torted, replace the synthesizer module, U300, and
retest.
27 
						

							28
NOTES