Motorola Commercial Series Operating and installation instructions

Commercial Series
CP040 Radios
VHF1 (136-162MHz)
Service Information
Issue: October 2004

ii
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in semiconductor memories or other media. Laws in the United States and other countries preserve for
Motorola certain exclusive rights for copyrighted computer programs, including the exclusive right to copy or
reproduce in any form, the copyrighted computer program. Accordingly, any copyrighted Motorola computer
programs contained in the Motorola products described in this manual may not be copied or reproduced in
any manner without the express written permission of Motorola. Furthermore, the purchase of Motorola
products shall not be deemed to grant, either directly or by implication, estoppel or otherwise, any license
under the copyrights, patents or patent applications of Motorola, except for the normal non-exclusive royalty-
free license to use that arises by operation of law in the sale of a product.

iii
Table of Contents
Chapter 1 MODEL CHART AND TECHNICAL SPECIFICATIONS
1.0 CP040 Model Chart .............................................................................................1-1
2.0 Technical Specifications ......................................................................................1-2
Chapter 2 THEORY OF OPERATION
1.0 Introduction ..........................................................................................................2-1
2.0 VHF (136-162MHz) Receiver..............................................................................2-1
2.1 Receiver Front-End .......................................................................................2-2
2.2 Receiver Back-End.........................................................................................2-3
3.0 VHF (136-162MHz) Transmitter...........................................................................2-4
3.1 Transmitter Power Amplifier ...........................................................................2-4
3.2 Antenna Switch...............................................................................................2-4
3.3 Harmonic Filter ...............................................................................................2-5
3.4 Antenna Matching Network ............................................................................2-5
3.5 Power Control.................................................................................................2-5
4.0 VHF (136-162MHz) Frequency Generation Circuitry...........................................2-6
4.1 Fractional-N Synthesizer ................................................................................2-7
4.2 Voltage Controlled Oscillator (VCO) ...............................................................2-8
Chapter 3 TROUBLESHOOTING TABLES
1.0 Troubleshooting Table for Receiver.....................................................................3-1
2.0 Troubleshooting Table for Synthesizer ................................................................3-3
3.0 Troubleshooting Table for Transmitter ................................................................3-4
4.0 Troubleshooting Table for Board and IC Signals ................................................3-6
Chapter 4 UHF PCB/SCHEMATICS/PARTS LISTS
1.0 Allocation of Schematics and Circuit Boards .......................................................4-1
1.1 VHF (136-162MHz) ........................................................................................4-1
1.2 Six Layer Circuit Board...................................................................................4-1
1.3 Speaker and Microphone Schematic..............................................................4-2
2.0 VHF PCB 8486769Z02-A Schematic Diagrams ..................................................4-3
3.0 VHF PCB 8486769Z02-A Parts List...................................................................4-11

iv

Chapter 1
MODEL CHART AND TECHNICAL SPECIFICATIONS
1.0 CP040 Model Chart
CP040 VHF1 136-162 MHz
Model Description
MDH50JDC9AA1_N CP040 136-162 MHz 5W 4-Ch
MDH50JDC9AA2_N CP040 136-162 MHz 5W 16-Ch
Item Description
X PMUD1981_ CP040 136-162 MHz 5W 4-Ch Tanapa
XPMUD1982_ CP040 136-162 MHz 5W 16-Ch Tanapa
XPMLD4239_ CP040, Back Cover Kit 136-162 MHz 4-Ch
XPMLD4240_ CP040, Back Cover Kit 136-162 MHz 16-Ch
X PMLN4552_ Plain, Front Housing Kit, 4-Ch
XPMLN4553_ Plain, Front Housing Kit, 16-Ch
XX NTN4497_R Li-Ion Battery, High Capacity
XXWPLN4166 Rapid Desktop Charger (Base Only)
XX EPNN7990_ Power Supply for Rapid Desktop Charger (UK)
XXEPNN7991_ Power Supply for Rapid Desktop Charger (Euro)
XX HLN8255 Belt Clip
XXHAD9338_ Antenna, 136-162 MHz, Heliflex
XX6866549D01_ CP040 Basic User Guide
XX6864117B25_ Safety Leaflet
XX6866546D03_ RTTE Leaflet
X = Indicates one of each is required

1-2 MODEL CHART AND TECHNICAL SPECIFICATIONS
2.0 Technical Specifications
Data is specified for +25°C unless otherwise stated.
General VHF1
Frequency: 136-162 MHz
Channel Capacity: 4 or 16 Channels
Power Supply: 7.5 Volts ±20%
Dimensions:
with High Capacity Li-Ion Battery and
with Standard NiMH Battery:
with Slim Li-Ion Battery:
128.7mm H x 61.7mm W x 44.1mm D
128.7mm H x 61.7mm W x 41.3mm D
Weight:
with Slim Li-Ion Battery
with High Capacity Li-Ion Battery:
with Standard NiMH Battery:
365g
420g
480g
Average Battery Life @ (5-5-90 Duty Cycle):
with Slim Li-Ion Battery:
with High Capacity Li-Ion Battery:
with Standard NiMH Battery:
1 W
17Hrs.
19 Hrs.
13 Hrs.
5 W
12 Hrs.
14 Hrs
10 Hrs

Technical Specifications 1-3
*Availability subject to the laws and regulations of individual countries.
Transmitter
Specifications VHF1
RF Output
NiMH @ 7.5V:
Low
1 W
High
5W
Frequency: 136-162 MHz
Channel Spacing: 12.5/20/25 kHz
Freq. Stability:
(-30°C to +60°C)
0.00025%
Spurs/Harmonics: -36 dBm < 1 GHz
-30 dBm > 1 GHz
Audio Response:
(from 6 dB/oct. Pre-emphasis, 300 to 3000Hz)
+1, -3 dB
Audio Distortion:@ 1000 Hz, 60% Rated Max. Dev. <3%
FM Noise: -40 dB (12.5 kHz)
-45 dB (25 kHz)
Receiver
Specifications VHF1
12.5 kHz
VHF1
20/25kHz
Frequency: 136-162 MHz
Sensitivity 12dB EIA SINAD: 0.25 µV (typical)
Adjacent Channel Selectivity: -65 dB -70 dB
Intermodulation: -70 dB
Freq. Stability (-30°C to +60°C): 0.00025%
Spur Rejection: -75 dB
Image and 1/2 I-F Rejection: -70 dB
Audio Output @ <5% Distortion: 500 mW
Self Quieter Frequencies
VHF1
151.200

1-4 MODEL CHART AND TECHNICAL SPECIFICATIONS

Chapter 2
THEORY OF OPERATION
1.0 Introduction
This Chapter provides a detailed theory of operation for the VHF circuits in the radio. Schematic
diagrams and board layout diagrams are included in Chapter 4 in this Section of the manual.
2.0 VHF (136-162MHz) Receiver
The VHF receiver covers the range of 136-162 MHz and provides switchable IF bandwidth for use
with 20/25/30 kHz or 12.5 kHz channel spacing systems. The receiver is divided into two major
blocks, as shown in Figure 2-1.
■Front End
■Back End
Figure 2-1 VHF Receiver Block Diagram
Demodulator
Crystal
Filter
1st Mixer
RF
Amp
IF
Amp
Preselector
Filter
Interstage
Filter
Recovered Audio
RSSI
RX from
Antenna Switch
Inj Filter
First LO
from Synthesizer
Ceramic
Resonator
Cer Fltr
Switching 4E
6E
6G
BW_SEL
12.5kHzFilter

2-2 THEORY OF OPERATION
2.1 Receiver Front End
Incoming RF signals from the antenna are first routed through the harmonic filter and antenna
switch, part of the transmitter circuitry, before being applied to the receiver front end. The receiver
front end consists of a preselector filter, RF amplifier, an interstage filter, and a double-balanced first
mixer.
The preselector filter is a fixed-tuned 4-pole design using discrete elements (L1-L4 and C1-C9) in a
series/shunt resonator configuration. It has a 3 dB bandwidth of 44 MHz, an insertion loss of 2 dB
and image attenuation of 37 dB at 226 MHz, with increasing attenuation at higher frequencies.
Diode CR1 protects the RF amplifier by limiting excessive RF levels.
The output of the filter is matched to the base of RF amplifier Q21, which provides 16 dB of gain and
a noise figure of 2 dB. Operating voltage is obtained from the 5R source, which is turned off during
transmit to reduce dissipation in Q21. Current mirror Q22 maintains the operating current of Q21
constant at 6.7 mA regardless of device and temperature variations, for optimum dynamic range
and noise figure.
The output of the RF amplifier is applied to the interstage filter, a fixed-tuned 3-pole series-coupled
resonator design having a 3 dB bandwidth of 54 MHz and insertion loss of 1.8 dB. This filter has an
image rejection of 40 dB at 226 MHz, with increasing attenuation at higher frequencies.
The output of the interstage filter is connected to the passive double-balanced mixer consisting of
components T41, T42, and CR41. This mixer has a conversion loss of 7 dB. High-side injection from
the frequency synthesizer is filtered by L40-L41 and C40-C44 to remove second harmonic energy
that may degrade half-IF spurious rejection performance. The injection filter has a 3 dB bandwidth
of 52 MHz and an insertion loss of 1.5 dB. The filtered injection signal is applied to T42 at a level of
+6 dBm.
The mixer output is applied to a diplexer network (L51-L52, C51, R51) which matches the 44.85
MHz IF signal to crystal filter FL51, and terminates the mixer into 50Ω at all other frequencies.

VHF (136-162MHz) Receiver 2-3
2.2 Receiver Back End
The receiver back end is a dual conversion design. High IF selectivity is provided by FL51, a 4-pole
fundamental mode 44.85 MHz crystal filter with a minimum 3 dB bandwidth of + 6.7 kHz, a
maximum 20 dB bandwidth of ±12.5 kHz, and a maximum insertion loss of 3.5 dB. The output is
matched to IF amplifier stage Q51 by L53 and C93. Q51 provides 16 dB of gain and a noise figure of
1.8 dB. The dc operating current is 1 mA. The output of Q51 is applied to the input of the receiver
IFIC U51. Diode CR51 limits the maximum RF level applied to the IFIC.
The IFIC is a low-voltage monolithic FM IF system incorporating a mixer/oscillator, two limiting IF
amplifiers, quadrature detector, logarithmic received signal strength indicator (RSSI), voltage
regulator and audio and RSSI op amps. The second LO frequency, 44.395 MHz, is determined by
Y51. The second mixer converts the 44.85 MHz high IF frequency to 455 kHz.
Additional IF selectivity is provided by two ceramic filters, FL52 (between the second mixer and IF
amp) and FL53 or FL54 (between the IF amp and the limiter input). The wider filter FL53 is used for
20/25 kHz channel spacing, and the narrower filter FL54 is used for 12.5 kHz channels. When the
BW_SEL line is high, the two upper diodes in packages D51 and D52 are forward biased, selecting
FL53 for 20/25 kHz channels. When the BW_SEL line is low, the two lower diodes in packages D51
and D52 are forward biased, selecting FL54 for 12.5 kHz channels.
Ceramic resonator Y70 provides phase vs. frequency characteristic required by the quadrature
detector, with 90 degree phase shift occurring at 455 kHz. Buffer Q70 provides a lower driving
impedance from the limiter to the resonator, improving the IF waveform and lowering the distortion
of the recovered audio signal. The recovered audio level at the DEMOD output is 100 mV rms (25
kHz channel, 3 kHz deviation) or 50 mV rms (12.5 kHz channel, 1.5 kHz deviation). An additional
RSSI output provides a DC voltage level that is proportional to RF signal level. This voltage is
measured by an A/D converter contained in the microprocessor (PE4_AN4, U401 pin 63).
FL52 FL53 FL54
Number of Elements: 4 6 6
Insertion Loss: 4 dB 4 dB 4 dB
6 dB Bandwidth: 15 kHz 15 kHz 9 kHz
50 dB Bandwidth: 30 kHz 30 kHz 22 kHz
Stopband Rejection: 27 dB 47 dB 47 dB

2-4 THEORY OF OPERATION
3.0 VHF Transmitter
The VHF transmitter covers the range of 136-162 MHz. Depending on model, the output power of
the transmitter is either switchable on a per-channel basis between high power (5 watts) and low
power (1 watt), or is factory preset to 2 watts. The transmitter is divided into four major blocks as
shown in Figure 2-2.
■Power Amplifier
■Harmonic Filter
■Antenna Matching Network
■Power Control.
Figure 2-2 VHF Transmitter Block Diagram
3.1 Transmitter Power Amplifier
The transmitter power amplifier has three stages of amplification. The first stage, Q100, operates in
Class AB from the 5T source. It provides 13 dB of gain and an output of 20 mW. The current drain is
typically 25mA. Components C105-C107 and L103 match the output of Q100 to the 50Ωinput of the
module U110.
U110 is a two stage Silicon MOS FET power amplifier module. Drain voltage is obtained from
UNSW B+ after being routed through current-sense resistor R150 in the power control circuit. The
output power of the module is controlled by varying the DC gate bias on U110 pin 2 (VGG).
3.2 Antenna Switch
The antenna switch consists of two pin diodes, D120 and D121. In the receive mode, both diodes
are off. Signals applied at the antenna or at jack J140 are routed, via the harmonic filter, through
network C122-C124 and L121, to the receiver input. In the transmit mode, Q170 is on and TXB+ is
present, forward-biasing both diodes into conduction. The diode current is 50 mA, set by R120-
R122. The transmitter RF from U110 is routed through D120, and via the harmonic filter to the
antenna jack. D121 conducts, shunting RF power and preventing it from reaching the receiver. L121
is selected to appear as a 1/4 wave at VHF, so that the low impedance of D121 appears as a high
impedance at the junction of D120 and the harmonic filter input. This provides a high series
impedance and low shunt impedance divider between the power amplifier output and receiver input.
Power Control
Harmonic Filter
Antenna
Matching
Network
Power Amplifier Module U110
Q100
TX_INJ
(From VCO)
5T
VDD
VGG
TX_ENA
PWR_SET
USWB+
RX_IN
(To Receiver)
Antenna
Switch
J140 Antenna
Jack
Antenna

VHF Transmitter 2-5
3.3 Harmonic Filter
The harmonic filter consists of components C130-C136 and L130-L132. The harmonic filter is a
seven-pole elliptical low-pass configuration, optimized for low insertion loss, with a 3 dB frequency
of approximately 180 MHz and typically less than 0.8 dB insertion loss in the passband.
3.4 Antenna Matching Network
The harmonic filter presents a 50Ωimpedance to antenna jack J140. A matching network, made up
of C140-C141 and L140, is used to match the antenna impedance to the harmonic filter. This
optimizes the performance of the transmitter and receiver into the impedance presented by the
antenna, significantly improving the antenna's efficiency.
3.5 Power Control
The power control circuit is a dc-coupled amplifier whose output is the dc gate bias voltage (VGG)
applied to the two stages of the RF power amplifier U110.
The output power of the transmitter is adjusted by varying the setting of the power-set DAC
contained in the ASFICcmp IC (DACG, U451 pin 6). This PWR_SET voltage is applied to
U150 pin 3.
Stage U150-2 compares the voltage drop across current sense resistor R150 to the voltage drop
across resistor R151 caused by current flow through Q150, and adjusts its output (pin 7) to maintain
equal voltages at pins 5 and 6. Thus the current flow through Q150, and hence its emitter voltage, is
proportional to the current drawn by stage U110, which is in turn proportional to the transmitter
output power. The emitter voltage of Q150 is applied to U150 pin 2, where it is compared to the
power set voltage PWR_SET at pin 3.
The output of U150 pin 1 is divided by R110 and R111 and applied as a gate voltage to the power
amplifier U110. By varying this gate voltage as needed to keep the voltages at U150 pins 2 and 3
equal, power is maintained at the desired setting. Excessive final current, for example due to
antenna mismatch, causes a lowering of the voltage at U150 pin 6, an increased voltage at pin 2,
and a lowering of the voltage at pin 1 and of the gate voltage VGG. This prevents damage to the final
stage due to excessive current.

2-6 THEORY OF OPERATION
4.0 VHF Frequency Generation Circuitry
The frequency generation system, shown in Figure 2-3, is composed of two circuit blocks, the
Fractional-N synthesizer IC U201, the VCO/Buffer IC U251, and associated circuitry. Figure 2-4
shows the peripheral interconnect and support circuitry used in the synthesizer block, and
Figure 2-5 details the internal circuitry of the VCOBIC and its interconnections to the surrounding
components. Refer to the schematic to identify reference designators.
The Fractional-N synthesizer is powered by regulated 5V and 3V provided by U310 and U330
respectively. 5V is applied to U201 pins 13 and 30, and 3V is applied to pins 5, 20, 34 and 36. The
synthesizer in turn generates a super-filtered 4.5V supply (VSF, from pin 28) to power U251. In
addition to the VCO, the synthesizer also interfaces with the logic and ASFICcmp circuits.
Programming for the synthesizer is accomplished through the microprocessor SPI_DATA_OUT,
SPI_CLK, and SYNTH_CS (chip select) lines (U409 pins 100, 1 and 47 respectively). A logic high
(3V) from U201 pin 4 indicates to the microprocessor that the synthesizer is locked.
Figure 2-3 VHF Frequency Generation Unit Block Diagram
Transmit modulation from the ASFICcmp (U451 pin 40) is applied to U201 pin 10 (MOD_IN). An
electronic attenuator in the ASFICcmp adjusts overall transmitter deviation by varying the audio
level applied to the synthesizer IC. Internally the audio is digitized by the Fractional-N synthesizer
and applied to the loop divider to provide the low-port modulation. The audio is also routed through
an internal attenuator for the purpose of balancing the low port and high port modulation and
reducing the deviation by 6 dB for 12.5 kHz channels, and is available at U201 pin 41 (VCO_MOD).
This audio signal is routed to the VCO's modulator.
Synthesizer
U201
VCOBIC
U251
Voltage
Multiplier
Loop
Filter
To Mixer
To PA Driver
VCP
Vmult1
Vmult2
Aux3
MOD Out
Modulating
Signal
Rx VCO
Circuit
Tx VCO
Circuit
TRB
16.8 MHz
Ref. Osc.
Rx Out
Tx Out
Buffer
Q280

VHF Frequency Generation Circuitry 2-7
4.1 Fractional-N Synthesizer
The Fractional-N synthesizer, shown in Figure 2-4, uses a 16.8 MHz crystal (Y201) to provide the
reference frequency for the system. External components C201-C203, R202 and D201 are also part
of the temperature-compensated oscillator circuit. The dc voltage applied to varactor D201 from
U201 pin 25 is determined by a temperature-compensation algorithm within U201, and is specific to
each crystal Y201, based on a unique code assigned to the crystal that identifies its temperature
characteristics. Stability is better than 2.5 ppm over temperatures of -30 to 60 °C. Software-
programmable electronic frequency adjustment is achieved by an internal DAC which provides a
frequency adjustment voltage from U201 pin 25 to varactor D201.
The synthesizer IC U201 further divides the 16.8 MHz signal to 2.1 MHz, 2.225 MHz, or 2.4 MHz for
use as reference frequencies. It also provides a buffered 16.8 MHz signal at U201 pin 19 for use by
the ASFICcmp.
To achieve fast locking of the synthesizer, an internal adapt charge pump provides higher current at
U201 pin 45 to quickly force the synthesizer within lock range. The required frequency is then locked
by the normal mode charge pump at pin 43. A loop filter (C243-C245 and R243-R245) removes
noise and spurs from the steering voltage applied to the VCO varactors, with additional filtering
located in the VCO circuit.
Both the normal and adapt charge pumps get their supply from the capacitive voltage multiplier
made up of C221-C224 and D220-D221. Two 3V square waves from U201 pins 14-15 provide the
drive signals for the voltage multiplier, which generates 12.1V at U201 pin 47. This voltage is filtered
by C225-C228.
One of the auxiliary outputs of the synthesizer IC (AUX3, U201 pin 2) provides the TRB signal which
determines the operating mode of the VCO, either receive or transmit.
Figure 2-4 VHF Synthesizer Block Diagram
DATA
CLK
CEX
MODIN
V
CC , 5V
XTAL1
WARP
PREIN
VCP
Reference
Oscillator
Voltage
Multiplier
Voltage
Controlled
Oscillator
2-Pole
Loop Filter
DATA (U401 Pin 100)
CLOCK (U401 Pin 1)
SYNTH_CS (U401 Pin 47)
MOD IN (U451 Pin 40)
+5V (U310 Pin 5)
7
8
9
10
13,30
23
25
32
47
VMULT2 VMULT1
BIAS1
SFOUT
AUX3
IADAPT
IOUT
GND
FREFOUT
LOCK 4
19
6,22,23,24
43
45
2
28
14 15
40
Filtered 5V
Steering
Line
LOCK (U401 Pin 56)
Prescaler In
LO RF
Injection
TX RF
Injection
(First Stage of PA)
FREF (U451 Pin 34)
39
BIAS2
41
+3V (U330 Pin 5) VDD, 3V MODOUT
U201
Low Voltage
Fractional-N
Synthesizer
5,20,34,36
TRB
VCO
Mod

2-8 THEORY OF OPERATION
4.2 Voltage Controlled Oscillator (VCO)
The VCOBIC (U251), shown in Figure 2-5, in conjunction with the Fractional-N synthesizer (U201)
generates RF in both the receive and the transmit modes of operation. The TRB line (U251 pin 19)
determines which oscillator and buffer are enabled. A sample of the RF signal from the enabled
oscillator is routed from U251 pin 12 through a low pass filter, to the prescaler input of the
synthesizer IC (U201 pin 32). After frequency comparison in the synthesizer, a resultant DC control
voltage is used to steer the VCO frequency. When the PLL is locked on frequency, this voltage can
vary between 3.0V and 9V. L251 and C252 further attenuate noise and spurs on the steering line
voltage.
In the receive mode, the TRB line (U251 pin 19) is low. This activates the receive VCO and the
receive buffer of U251, which operate within the range of 190.85 to 218.85 MHz. The VCO
frequency is determined by tank inductor L254, C253-C257, and varactor D251. The buffered RF
signal at U251 pin 8 is further amplified by Q280 and applied as RX_INJ to the low-pass injection
filter in the receiver front end circuit.
In the transmit mode, U251-19 is driven high by U201 pin 2, enabling the transmit VCO and buffer.
The 136-162 MHz RF signal from U251 pin 10 is applied as TX_INJ to the input of the transmitter
circuit via matching network C290-C291 and L291. TX VCO frequency is determined by L264,
C263-C267, and varactor D262. High-port audio modulation from the synthesizer IC is applied as
VCO_MOD to varactor D261 which modulates the transmit VCO.
Figure 2-5 VHF VCO Block Diagram
Presc
RX
TX
Matching
Network
Pin 8
Pin 14
Pin 10
3V (U330 Pin 5)
VCC Buffers
U201 Pin 32
AUX3 (U201 Pin 2)
Prescaler Out
Pin 12
Pin 19
Pin 20
TX/RX/BS
Switching Network
U251
VCOBIC
Rx Active
Bias
Tx Active
Bias
Pin 2
Rx-I adjust
Pin 1
Tx-I adjust
Pins 9,11,17
Pin 18
Vsens
Circuit
Pin 15
Pin 16
TX VCO
Circuit
TX
Tank
RX VCO
Circuit
RX
Tank
Pin 7
Vcc-Superfilter
Collector/RF in
Pin 4
Pin 5
Pin 6
RX
TX
V_SF (U201 Pin 28)
NC
NC
Vcc-Logic
3V
(U330 Pin 5)
Steer Line
Voltage
(V_STEER)
Pin 13
Pin 3
TRB_IN
Buffer
Q280
RX INJ
V_SF
(U201 Pin 28)
TX INJ

Chapter 3
TROUBLESHOOTING TABLES
This section contains detailed troubleshooting tables. These tables should be used as a guide in
determining the problem areas. They are not a substitute for knowledge of circuit operation and
astute troubleshooting techniques. It is advisable to refer to the related detailed circuit descriptions
in the theory of operation sections prior to troubleshooting a radio.
Most troubleshooting tables end up by pointing to an IC to replace. It is not always noted, but it is
good practice to verify supplies and grounds to the affected IC and to trace continuity to the
malfunctioning signal and related circuitry before replacing any IC. For instance, if a clock signal is
not available at a destination, continuity from the source IC should be checked before replacing the
source IC.
1.0 Troubleshooting Table for Receiver
Symptom Possible Causes Procedure Corrective Action
Radio Dead (no
turn-on beep, no
LED indication)
1. Battery dead or
defective.
Substitute known good battery or
battery eliminator.
Charge or replace battery.
2. Defective battery
contacts.
Inspect battery contacts for corrosion
or bent terminals.
Clean/repair/replace J301.
3. Blown fuse Check voltage on each side of fuse.
If blown, 0 VDC after fuse.
Check for short on output,
check D301, VR301, trouble-
shoot/repair as needed, replace
fuse.
4. DC switching fault Verify battery voltage present at
S444 pin 5 when radio is on.
Verify Q494-1 is at least 1V dc,
Q494-6 is ~0.1V dc, Q493-3 is at
Vbatt.
Check/replace on-off-volume
control S444.
Troubleshoot/replace Q493/4.
5. Microprocessor not
starting up.
Verify clock input to U401-90
(EXTAL) is 7.3975 MHz using high
impedance probe. If clock is 3.8MHz,
check for shorts on U401 pins.
Connect RIB to verify
communication via CPS.
Verify U401-94 (RESET) is high.
Verify 16.8 MHz signal at U451-
34. If OK, troubleshoot/replace
U451. If not present, trouble-
shoot U201 Synthesizer.
Reprogram/reflash as needed.
If RESET is Low, troubleshoot
regulator U320. Check for
shorts at U401 pins. Replace
U401 (depot only). Reprogram/
reflash as needed.
6. Regulator fault Verify U310-5 is 5V dc, U320-5 is
3.3V dc, U330-5 is 3V dc.
Check for shorts on outputs,
troubleshoot/repair as needed,
replace faulty regulator.

3-2 TROUBLESHOOTING TABLES
No Audio 1. Synthesizer out of lock Verify U201-4 is at 3V dc. Troubleshoot synthesizer/VCO
circuits.
2. Defective IFIC Verify audio is present at U51-8. Check Q70, Y70, U51.
3. RX audio buffer fault Verify audio is present at U451-2. Check U510 and associated
parts.
4. ASFIC fault Verify audio is present at U451-41.
Verify U451-14 is high.
Check squelch setting, PL/DPL
programming. Troubleshoot/
replace U451.
5. Audio PA fault Verify U490-1 is <0.2V dc.
Verify audio is present at U490-5
and 8.
Check Q490.
Check/replace U490.
6. Defective speaker Verify audio is present at speaker
terminals.
If not, check continuity of J471-2
and 3. Check J491. If yes,
replace speaker.
No Receive
(squelch noise
present)
1. No first injection Check that RF level at T42-6 is
approx +6 dBm.
Check that RF level at U251-8 is at
least -8 dBm.
Check injection filter C40-44,
L40-41.
If yes, check Q280 and associ-
ated parts. If no, check U251
and components on pins 5 and
6.
2. No 5R source. Verify U401-49 is high in RX.
Verify Q311 gate is 0V dc in RX
Verify Q311 drain is 5V dc in RX.
Check/replace U401
Check/replace Q313.
Check for shorts, check/replace
Q311.
3. Harmonic filter or
antenna switch fault
Apply on-channel 100 mV RF signal
at antenna port. Verify RF level at jct.
C1/C2 per schematic.
Check TX harmonic filter, D120-
121. Should be 0V dc on D120-
121.
4. Back end fault Apply on-channel 100 mV RF signal
at antenna port. Measure RF levels
from FL51 through U51.
Check components prior to
loss-of-signal point.
5. No second injection Measure RF level at U51-3, verify
approx. 280 mV rms.
If dc voltages at U51-3 and 4
are OK, check Y51 and
associated parts. If not replace
U51.
Symptom Possible Causes Procedure Corrective Action

Troubleshooting Table for Synthesizer 3-3
2.0 Troubleshooting Table for Synthesizer
Symptom Possible Causes Procedure Corrective Action
Synthesizer Out of
Lock (RX mode
only)
1. VCO fault Verify oscillator is working, check RF
level at U251-10 per schematic.
Check dc voltages at U251 pin 2
through 6 and 10 per Board and IC
troubleshooting table.
Verify steering line voltage is
between ~3V and 10V.
Check VCO tank components
connected to U251-5 and 6.
Check for shorts/opens, replace
U251.
Check D251 and associated
components.
2. Synthesizer fault Verify TRB line (from U201-2 to
U251-19) is low in RX mode
Check for shorts, check U201
voltages per Board and IC
troubleshooting table, replace
U201 if incorrect.
3. Programming fault Verify RX channel programming is
correct.
Re-program if necessary.
Synthesizer Out of
Lock (TX mode
only)
1. VCO fault Verify oscillator is working, check RF
level at U251-10 per schematic.
Check dc voltages at U251 pins
1,3,4,10,15,16 per Board and IC
troubleshooting table.
Verify steering line voltage is
between ~3V and 10V.
Check VCO tank components
connected to U251-15 and 16.
Check for shorts/opens, replace
U251.
Check D261 and associated
components.
2. Synthesizer fault Verify TRB line (U201-2 to U251-19)
is high (3V) in TX mode
Check for shorts, check U201
voltages per Board and IC
troubleshooting table, replace
U201 if incorrect.
3. Programming fault Verify TX channel programming is
correct.
Re-program if necessary.
Synthesizer Out of
Lock (RX and TX
modes)
1. VCO fault Check that RF level at U251-12 is at
least 150 mV (VHF)
If low/missing, check L276,
C276-7, R276.
2. Synthesizer fault Check that RF level at U201-32 is at
least 150 mV (VHF).
Verify steering line voltage is
between ~3V and 10V.
If correct, check/replace U201.
If incorrect, check R248 and
C241.
Check loop filter components
R243-5 and C243-5.
3. DC voltage fault Verify 4.5V dc at U201-28.
Verify 12.1V dc at U201-47
Check C231-233, etc., for
shorts. If OK check/replace
U201.
Check for 3V 1.05 MHz sq
waves at U201-14 and 15.
Check C218-228, D220-221.
4. Programming fault Verify channel programming is cor-
rect.
Re-program if necessary.

3-4 TROUBLESHOOTING TABLES
3.0 Troubleshooting Table for Transmitter
Symptom Possible Causes Procedure Corrective Action
No Transmit (no
TX LED indication)
1. PTT switch defective. Verify U401-71 goes low when PTT
is pressed.
Replace PTT switch S441.
2. EXT MIC PTT fault Verify U401-72 goes low when J471-
4 is grounded.
Check/replace Q470, L471 etc.
No Transmit (TX
LED indication OK)
1. Synthesizer out of lock Refer to Synthesiser trouble-
shooting table.
Refer to Synthesiser trouble-
shooting table.
2. No TX_ENABLE Verify U401-50 is high when pin 71
or 72 is low.
Check/replace U401.
3. TX DC switch fault Verify Q171-C is 0V in TX.
Verify Q170-C is at Vbatt in TX.
Replace Q171.
Check for shorts, replace Q170.
4. Power control fault Check Q150 and U150 dc voltages
per schematic and Synthesiser
troubleshooting table.
Repair/replace defective com-
ponents
5. No TX injection Check that RF level at jct. R100/
R101 per schematic.
Check U251, L291-292, C290-
291.
6. No 5T source Verify Q312 gate is 0V dc in TX
Verify Q312 drain is 5V dc in TX.
Check/replace Q313.
Check for shorts, check/replace
Q312.
7. TX gain stage failure Check RF levels at Q100 and U110
per schematic.
Troubleshoot Q100/U110 and
associated circuitry.
8. Antenna switch failure Verify dc voltage at jct. R122/L120 is
approx 1.5V.
Check/replace D120-121, L120-
121, R120-122, etc.
Low Power 1. Low TX injection Check that RF level at jct. R100/
R101 per schematic.
Check U251, L291-292, C290-
291.
2. Low gain in TX stage Verify dc voltage at Q100-E is ~1.3V
(VHF).
Verify that RF level at U110-1 is
approx. 1V (VHF).
Verify 5T voltage is correct.
Troubleshoot Q100 circuitry.
Troubleshoot Q100 circuitry.
Check/replace Q100.
3. Incorrect control volt-
age
Verify that the dc voltage at
PWR_SET (R162) is approx 1.8V dc
(at 1 watt) to 2.6V dc (at 4-5 watts).
Verify that the dc voltage at U110-2
is approx 2-3V dc (at 1 watt) to 3-4V
dc (at 4-5 watts). (See schematic.)
Check programming. Trouble-
shoot controller circuitry. Check/
replace U451.
Troubleshoot U150, Q150 and
associated circuitry.
4. Antenna switch defect Verify dc voltage at jct. R122/L120
(VHF) is approx 1.7V.
Note: Do not
attempt to measure RF or DC
voltages at the diodes. Damage to
test equipment may occur.
Check/replace D120-121, L120-
121, R120-122, etc.
5. Harmonic filter defect Visually inspect components C130-
137, L130-132. Check dc continuity
of L130-132
in RX mode only .
Repair/replace if necessary.