Motorola Astro Digitalport Saber Basic 68p81076c05 Manual

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SECTION VII.  BASIC THEORY OF OPERATION
A. Introduction to This Section
The following theory will help isolate the problem
to a particular board. Using circuit board replacement
as the basic service approach will maximize working-
time of the radio.
B. General Overview
The ASTRO Digital SABER radio is a wideband,
synthesized, fixed-tuned radio available in the 
VHF, UHF, and 800MHz bands. All ASTRO Digital
SABER radios are capable of both analog operation 
and ASTRO mode (digital) in 12.5kHz or 25kHz 
bandwidths.
The ASTRO Digital SABER radio consists of four
major assemblies. They are:
¥Controller Board- contains the microcontrol unit
(MCU) and its associated memory and memory
management integrated circuit (IC), the digital sig-
nal processor and its associated memories and
support IC, the audio power amplifier, and a
switching regulator. 
¥RF Board- contains all transmit, receive, and fre-
quency generation circuitry including the digital
receiver back-end IC and the reference oscillator.
¥Display/Keypad Assemblies- contain the inter-
nal microphone and speaker, a two-line liquid
crystal display (LCD), and a 3 x 6 keypad.
¥Control Top- contains switches for volume and
mode selection, push-to-talk (PTT), monitor, and
several function-selectable switches.
C. Analog Mode of Operation
When the radio is 
receiving, the signal comes from
the antenna/antenna-switch connector to the RF
board, passes through the RX/TX switch and the
receiver front end. The signal is then filtered, ampli-
fied, and mixed with the first local-oscillator signal
generated by the voltage-controlled oscillator (VCO).
The resulting intermediate frequency (IF) signal is fed
to the IF circuitry, where it is again filtered and ampli-
fied. This amplified signal is passed to the digital
back-end IC, where it is mixed with the second local
oscillator to create the second IF at 450kHz. It is then
converted to a digital bit stream and mixed a third time
to produce a baseband signal. This signal is passed to
the controller board through a current-driven differen-
tial output. On the controller board, the digital-
signal-processor-support IC digitally filters and dis-criminates the signal, and passes it to the digital-signal
processor (DSP). The DSP decodes the information in
the signal and identifies the appropriate destination for
it. For a voice signal, the DSP will route the digital
voice data to the DSP-support IC for conversion to an
analog signal. The DSP-support IC will then present
the signal to the audio power amplifier, which drives
the speaker. For signalling information, the 
DSP will decode the message and pass it to the
microcontrol unit.
When the radio is 
transmitting, microphone audio
is passed from the audio power amplifier (PA) to the
DSP-support IC, where the signal is digitized. The
DSP-support IC passes digital data to the DSP, where
pre-emphasis and low-pass (splatter) filtering are
done. The DSP returns this signal to the DSP-support
IC, where it is reconverted into an analog signal and
scaled for application to the voltage-controlled oscilla-
tor as a modulation signal. Transmitted signalling
information is accepted by the DSP from the micro-
control unit, coded appropriately, and passed to the
DSP-support IC, which handles it the same as a voice
signal. Modulation information is passed to the synthe-
sizer along the modulation line. A modulated carrier is
provided to the RF PA, which transmits the signal
under dynamic power control.
D. ASTRO Mode of Operation
In the ASTRO mode (digital mode) of operation,
the transmitted or received signal is limited to a dis-
crete set of deviation levels, instead of continuously
varying. The receiver handles an ASTRO-mode signal
identically to an analog-mode signal up to the point
where the DSP decodes the received data. In the
ASTRO receive mode, the DSP uses a specifically
defined algorithm to recover information. In the
ASTRO transmit mode, microphone audio is pro-
cessed identically to an analog mode with the
exception of the algorithm the DSP uses to encode the
information. This algorithm will result in deviation lev-
els that are limited to discrete levels.
E. RF Board Basic Theory of Operation
The receiver front end consists of a preselector,
an RF amplifier, a second preselector, and a mixer.
Both preselectors in the VHF and UHF radios are var-
actor-tuned, two-pole filters controlled by the
microcontrol unit through the digital/analog (D/A) IC.
On the 800MHz receiver front end, these filters are
fixed-tuned. The RF amplifier is a dual-gate, gallium-
arsenide based IC. The mixer is a double-balanced, 
						

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active mixer coupled by transformers. Injection is pro-
vided by the VCO through an injection filter. See Table
14 for local oscillator (LO) and first IF information.
The frequency generation function is performed by
three ICs and associated circuitry. The reference oscil-
lator provides a frequency standard to the
synthesizer/prescaler IC, which controls the VCO IC.
The VCO IC actually generates the first LO and trans-
mit-injection signals and buffers them to the required
power level. The synthesizer/prescaler circuit module
incorporates frequency-division and comparison cir-
cuitry to keep the VCO signals stable. The
synthesizer/prescaler IC is controlled by the microcon-
trol unit through a serial bus. Most of the synthesizer
circuitry is enclosed in rigid metal cans on the RF
board to reduce microphonic effects. 
The receiver back end consists of a two-pole crys-
tal filter, an IF amplifier, a second two-pole crystal
filter, and the digital back-end IC. The two-pole filters
are wide enough to accommodate 5kHz modulation.
Final IF filtering is done digitally in the DSP-support
IC.
The digital back-end IC consists of an amplifier,
the second mixer, an IF analog-to-digital converter, a
baseband down-converter, and a 2.4MHz synthesis
circuit to provide a clock to the DSP-support IC on the
controller board. The second LO is generated by dis-
crete components external to the IC. The output of the
digital back-end IC is a digital bit stream that is current
driven on a differential pair for a reduction in noise
generation.
The transmitter consists of an RF PA IC that gets
an injection signal from the VCO. Transmit power is
controlled by two custom ICs that monitor the output of
a directional coupler and adjust PA control voltages
correspondingly. The signal passes through a RX/TX
switch that uses PIN diodes to automatically provide
an appropriate interface to transmit or receive signals.
Antenna selection is done mechanically in the control
top.
F. Controller Board Basic Theory of Operation
The controller board contains the radioÕs micro-
control unit with its memory and support circuits,
voltage regulators, audio, DSP, and power control cir-
cuits. Connected to the controller board are the
display board, RF board, and control top.The microcontrol unit controls receive/transmit fre-
quencies, power levels, display, and other radio
functions, using either direct logic control or serial
communications paths to the devices.The microcontrol
unit executes a stored program located in the FLASH
ROM. Data is transferred to and from memory by the
microcontrol unit data bus. The memory location from
which data is read, or to which data is written, is
selected by the address lines.
The support-logic IC acts as an extension of the
microcontrol unit by providing logic functions such as
lower address latch, reset, memory address decoding,
and additional control lines for the radio. The micro-
control unit controls the crystal-pull circuit to adjust the
crystal oscillatorÕs frequency on the microcontrol unit,
so that the E-clockÕ s harmonics do not cause interfer-
ence with the radioÕs receive channel.
The regulator and power-control circuits include
an unswitched +5V discrete circuit and the
regulator/power-control IC. Switched +5V is used for
all circuits on the controller board except the audio PA,
which is sourced from 7.5V. The regulator automati-
cally provides 5V when the radio is turned on. The
regulatorÕs power-down mode is controlled by the
microcontrol unit, which senses the position of the
on/off switch.
The DSP performs signalling and voice encoding
and decoding as well as audio filtering and volume
control. This IC performs Private-Line
¨/Digital Private
Lineª (PL/DPL) encode and alert-tone generation.
The IC transmits pre-emphasis on analog signals and
applies a low-pass (splatter) filter to all transmitted sig-
nals. It requires a 33MHz crystal to function. An 8kHz
interrupt signal generated by the DSP-support IC is
also required for functionality. It is programmed using
parallel programming from the microcontrol unit and
the DSP-support IC.
The DSP-support IC performs analog-to-digital
and digital-to-analog conversions on audio signals. It
contains attenuators for volume, squelch, deviation,
and compensation, and it executes receiver filtering
and discrimination. The IC requires a 2.4MHz clock to
function (generated by the digital back-end IC) and is
programmed by the microcontrol unit SPI bus.
LO Frequency Range 181.15-223.15MHz 329.65-446.65MHz 732.65-796.65MHz
First IF Frequency 45.15MHz 73.35MHz 73.35MHz
VHF UHF 800MHz
Table 14.  Local Oscillator and First IF Frequencies 
						

							A. Introduction to This Section
This section of the manual contains troubleshoot-
ing charts, error codes, a functional block diagram,
interconnect diagrams, and flexible circuit information.
This section will help you isolate a problem to the
board level. Board-level troubleshooting does not
attempt to isolate problems to the component level.
Component-level service information can be found in
the ÒASTRO Digital SABER Portable Radios Detailed
Service Manual.Ó (Refer to ÒRelated Publications Avail-
able SeparatelyÓ list located in the front section of this
manual.)
NOTE
To access the various connector pins, use the
housing eliminator/test fixture along with the dia-
grams found in this section of the manual. (Refer to
the ÒService Aids for Board-Level TroubleshootingÓ
table for the appropriate Motorola housing elimina-
tor/test fixture part number.)
B. Replacement Board Procedures
Once a problem has been narrowed down to a
specific board, it is important to get the customerÕs
radio back in service as quickly as possible. This can
be done several ways:
1. Install a good board from your inventory into the
customerÕs radio.2. Order a replacement board from Worldwide Sys-
tem and Aftermarket Products Division at
1-800-422-4210.
3. Troubleshoot the defective board using the
ÒASTRO Digital SABER Portable Radios Detailed
Service Manual.Ó (Refer to the ÒRelated Publica-
tions Available SeparatelyÓ list located in the front
section of this manual for the specific manual
number.)
C. Power-Up Error Codes
When the radio is turned on (power-up), the radio
performs cursory tests to determine if its basic elec-
tronics and software are in working order. Problems
detected during these tests are presented as error
codes on the radioÕs display. The presence of an error
should prompt the user that a problem exists and that
a service technician should be contacted.
Self-test errors are classified as either fatal or non-
fatal. Fatal errors will inhibit user operation; non-fatal
errors will not. Use Table 15 to aid in understanding
particular power-up error code displays.
SECTION VIII.  BOARD-LEVEL TROUBLESHOOTING
Table 15.  Power-Up Error Code Displays
Note:If the corrective action does not fix the failure, replace the controller board.
Error Code Description Corrective Action
01/81 ROM Checksum Failure Reprogram the FLASH memory.
01/02 External EEprom Checksum Non-Fatal Error Reprogram codeplug.
01/82 External EEprom Checksum Failure Reprogram the codeplug.
01/88 RAM Failure  - Note: not a checksum failure Turn the radio off, then on.
01/90 General Hardware Failure Turn the radio off, then on.
01/92 Internal EEPROM Checksum Failure Reprogram the codeplug.
02/10 DSP support IC checksum Non-Fatal Error Turn the radio off, then on.
02/81 DSP ROM Checksum Failure Reprogram the FLASH memory.
02/88 DSP RAM Failure  - Note: not a checksum failure Turn the radio off, then on.
02/90 General DSP Hardware Failure Turn the radio off, then on.
(DSP startup message not received correctly)
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							D. Operational Error Codes
During radio operation, the radio performs dynam-
ic tests to determine if the radio is working properly.
Problems detected during these tests are presented
as error codes on the radioÕs display. The presence ofan error code should prompt a user that a problem
exists and that a service technician should be contact-
ed. Use Table 16 to aid in understanding  particular
operational error codes.
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Table 16.  Operational Error Code Displays
Error Code Description Corrective Action
FAIL 001 Synthesizer Out-of-Lock a. Reprogram codeplug
b. Replace RF Board
FAIL 002 Selected Mode/Zone Codeplug Checksum Error Reprogram codeplug
Table 17.  Receiver Troubleshooting Chart
Symptom Possible Cause Correction or Test (Measurements Taken at Room Temperature)
Radio Dead; 1.  Dead Battery Replace with charged battery.
Display Does 2.  Blown Fuse Check see-through fuse on RF board near the B+ connector.
Not Light Up 3.  On/Off Switch With the radio on, check for B+ SENSE at P901 pin 10 of the control top/
PTT flex; if not there, check for UNSW B+ at pin 19 of RF board connector; 
if not there, replace the RF board; if there, replace the controller 
board.
4.  Regulators Check for +5V at P901 pin 5 of the control top/PTT flex; 
if not there, replace the controller board.
Radio Dead; 1.  Controller Check board for communication with RSS. If no communication,
Display Board replace controller board.
Lights Up 2.  RF Board Check the ODC (output data clock) at pin 8 of the RF board 
connector for 2.4MHz. If not there, replace RF board.
No Receiver 1.  Programming a.  Does the transmitted signal match the receiver 
Audio or configuration (PL, DPL, etc.)?
Receiver Does b.  With the monitor function enabled, can the radio be unmuted?
Not Unmute
Audio Distorted 1.  Synthesizer Check synthesizer frequency by measuring the transmitter frequency; 
or Not Loud Not On if off by more than ±250Hz, realign.
Enough Frequency
RF Sensitivity 1.  Synthesizer Check synthesizer frequency by measuring the transmitter frequency;
Poor Not On if off by more than ²±600Hz, realign.
Frequency
2.  Antenna Switch Visually check for proper mechanical positioning of the antenna switch
to the RF board; re-position if necessary. Then, check for electrical
continuity between the center pin of the antenna connector and the
RF board; replace defective item.
3.  Receiver Check RF front-end tuning for optimum sensitivity using the RSS.
Front-End
Tuning
(VHF/UHF only)
Radio Will 1.  Controller Does B+ SENSE at P901 pin 10 of the control top/PTT flex switch on and
Not Turn Off Board off as the on/off switch is operated? If not, replace the controller board. 
						

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Symptom Possible Cause Correction or Test (Measurements Taken at Room Temperature)
No RF Power 1.  TX Power Level Check TX power level and frequency programming (from RSS).
Out or Frequency
2.  No PTT From With the PTT switch depressed (radio transmitting/keyed), check for INT PTT 
Control Top at P901 pin 6 of the control top/PTT flex; 
if not there, replace the control top/PTT flex.
3.  No Injection To Check LOCK DETECT at pin 13 of the RF board connector; 
Power Amplifier if not between 1.0 and 4.5V, replace the RF board.
No Modulation; 1.  Programming Check deviation and compensation settings using the RSS.
Distorted 2.  Controller With a 1kHz tone at 80mVrms injected at the external microphone, is the 
Modulation Board output of the controller board to RF board connector pin 15 distorted? 
If so, replace the controller board.
Bad Microphone 1.  Check Realign if necessary.
Sensitivity Deviation and
Compensation
2.  Microphone Speaking loudly into the microphone, monitor the output voltage (INT MIC)
at the speaker microphone flex connector, P701 pin 4. 
If not 2mVrms, replace the speaker/microphone and front shield assembly.
No/Low 1.  Check
Signalling Programming
(PL, DPL, MDC) 2.  Controller Check for proper modulation at the RF board to controller board 
Board connector pin 15; if not there, replace the controller board.
CanÕt Set 1.  RF Board If maximum deviation can be set to > 5.0kHz, but compensation 
Compensation cannot be set, replace the RF board.
Table 18.  Transmitter Troubleshooting Chart 
						

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NOTES