Motorola Two Way Portable Radio Ht Series Detailed Rev 6881088c46 E Manual

							FMR-2045A-2December 26, 2003
UHF Troubleshooting Charts: Troubleshooting Flow Chart for Controller 31
Chapter 3 UHF Troubleshooting Charts
3.1 Troubleshooting Flow Chart for Controller
MCU Check
Power Up 
Alert Tone
 OK?
Speaker
OK?
U409 EXTAL= 
7.3728 MHz? 
U201 Pin 19 
16.8 MHz
5V at U247?
3.3V at U248?
U409 Reset Pin 
94 High?
MCU is OK
Not able to 
program RF 
Board ICsBefore replacing 
MCU, check SPI 
clock, SPI data, 
and RF IC select 
Replace 
Speaker
Read Radio 
OK? 
Check 
Setup
Reprogram the 
correct data. 
See FGU 
Troubleshooting
7.5V at 
Pin 3/5 U247? 
4/3.3V at Pin 1 
U248Check 
Q400
Replace 
U247/U248
Check any short to 
SWB+, 
Vdda or Vddd
Press PTT. Red 
LED does not 
light up
PTT U409 
Pin 53 
low?
Press PTT 
Q502-2 
High?
Check 
PB504
Check 
Q502-2 
voltage
LED 
Q502,R501 
OK?
Replace 
Faulty 
Component
Check 
Accessories J403 
OPT_SEL_1 & 
OPT_SEL_2 
Pin 8 & 9 
low?
Radio could 
not PTT 
externally
U409 
Pin 52, 6 
low?
See FGU 
Troubleshooting 
chart
LED should 
light up
Check 
MCU
PTT
NO
YES
YES
No
No
NO
YESYES
NOYESYES
NO
NO
YES
YES
NO
NO
YES
NO
YES
NO
YESYESNO NO
YES
EXT
SPKR EXT
PTT INT
AUDIO
J403 Pin 9 low? 
Pin 8 high?
ASFIC U404 
Pin 14 & 15 
high?
Check 
Accessories
Check 
U404
Check 
U420 Audio PA
NO
NO YES
YES J403 Audio 
at Pin 2 & 
Pin 3
Check Spk. Flex 
Connection
Audio
at Audio
PA (U420) 
input (U447)
Audio from Pin 41 
ASFIC, U404?
Check 
ASFIC U404
Check
 Audio PA 
(U420)
Check 
U301
 IF ICAudio at 
Pin 2 
U404?
NO
NO
NO YESYES
NO
YES 
						

							December 26, 2003FMR-2045A-2
32UHF Troubleshooting Charts: Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)
3.2 Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)
Bad SINAD
Bad 20dB Quieting
No Recovered AudioSTART
Audio at pin 8 
of U301?Check ControllerYe s
No
Spray or inject 1st IF 44.85 
MHz into 
XTAL Filter
Audio heard?BYe s
No
Check 2nd LO signal 
44.395 MHz at C367
Signal 
Present?BYe s
Voltages 
ok?
Biasing ok?
Check circuitry 
around U301. 
Replace U301 if 
defect
No
No
A
Ye sCheck Q302 bias 
circuitry for faults.
Rotate Freq. Knob
Replace Q302.
Go to B
Ye s
No
Check voltages on 
U301
Check circuitry 
around Y300. 
Replace Y300 if 
defect 
						

							FMR-2045A-2December 26, 2003
UHF Troubleshooting Charts: Troubleshooting Flow Chart for Receiver (Sheet 2 of 2) 33
3.3 Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)
IF Signal at 
L311?
No
RF Signal
at T301?
RF Signal
at C310?
No
RF Signal
at C307?
No
RF Signal
at C301?
No or 
Check harmonic filters L101 & L102 and 
ant. switches CR101, CR102, L104
Check filter between 
C301 & C307; program 
filter to schematic test 
freq and check varactor 
voltages.
Inject RF into J101
Are varactor 
voltages OK?
No
Ye s
Check RF amp (Q301) 
Stage.
Check filter between 
C310 & T301.
Ye s
Check T301, T302, 
CR306, R308, R309
Ye s
1st LO O/P 
OK?
Locked?Ye s
Check FGU
Ye s
Trace IF signal 
from L311 to 
Q302. Check for 
bad XTAL filter.
No
Ye sQ302 collec-
tor OK?
IF signal 
present?
Before replacing 
U301, check 
U301 voltages; 
trace IF signal 
path.
Ye s
Check for 3.0 
VDC
Is R5 
present?
Check Q210, U201 
(pin 48) voltages and 
U247
No
No
No
Check U404 voltage. 
U404 can be selected by 
MCU before replacing 
U404.
Check varactor filter.
NoYe s
Ye s
Ye s
A
A
B
weak RF 
						

							December 26, 2003FMR-2045A-2
34UHF Troubleshooting Charts: Troubleshooting Flow Chart for Transmitter
3.4 Troubleshooting Flow Chart for Transmitter
START
No Power
Is There B+ 
Bias for Ant 
switchC h e c k  Q 111
Is Current 
OK?Is Control Volt-
age High or LowCheck PCIC
1. Check Pin Diodes
2. Check Harmonic Filter
Inspect/Repair Tx
Output Network
Is Power 
OK?
Done
Check Drive to 
Module
Is Drive 
OK?
Troubleshoot 
VCO
Inspect PA Network/
Check Power Out of 
U101 at Cap C160
Is Power 
OK?
Replace U101
Is Power 
OK?
Replace Q101
Done
Done
No
Ye s
Ye sNo
No
Ye sLow
High
No
Ye s
Ye s
No
Ye s
No 
						

							FMR-2045A-2December 26, 2003
UHF Troubleshooting Charts: Troubleshooting Flow Chart for Synthesizer 35
3.5 Troubleshooting Flow Chart for Synthesizer
5V
 at pin 6 of 
CR201
Is information
from µP U409
correct?
Is U201 Pin 
18 AT 4.54 
VDC?
Is U201 Pin 
47AT = 13 
VDC
Is U241 Pin 19
4.3 VDC in TX?
Sta rt
Visual 
check of the 
Board OK?Correct
Problem
Check 5V
Regulator
+5V at U201
Pin’s
13 & 30?
Is 16.8MHz
Signal at
U201 Pin 19?
Check FL201, C206, 
C207, C208, CR203 
& R204
Are signals
at Pin’s 14 &
15 of U201?
Check 
L202Check Q260, 
Q261 & R260
U201 pin 2 at 
>3V in Tx and 
-30 dBm?
Are R231,R232,
R233,C231,C232,
& C233 OK?
Replace U201
If L261, C263 & C264
are OK, then see VCO
troubleshooting chart
Are Waveforms
at Pins 14 & 15
triangular?
Do Pins 7,8 & 9
of U201 toggle
when channel is
changed?
Check programming
lines between U409
and U201 Pins 7,8 & 9
Replace U201
Check uP U409
Troubleshooting
Chart
NO
YES
NO
YES
NO
YES
NO
YESNO
NO
NO
YES
YESNOYES YESNO
YES YES YES
NONO
NO
NO
YES
NO
YES YESCheck CR201, 
U210, U211, C258, 
C259 & C228
3.3V at U201 
pins 5, 20, 34 
& 36Check U248, 
L201 & L202
Is 
16.8MHz 
signal at 
U201 pin 
23?
Replace 
U201
YES
NO NO
YES
NO YES 
						

							December 26, 2003FMR-2045A-2
36UHF Troubleshooting Charts: Troubleshooting Flow Chart for VCO
3.6Troubleshooting Flow Chart for VCO
START
No LO?
Tx Carrier?
VCO OK
Check 
R260
TRB = 5V?Pin 10 
>1V?
L253 O/C?Change 
L253
Change 
U241
AUX 3 
High?
Check U201 
Pin 2 for 3.2V
Pin 19 
=0V
AUX 4 
High?
Change 
Q261
V ctrl 0V 
or 13V?
L243 Open 
Circuit?
Change 
U241
Change 
L243
Change 
U201
Check for faulty parts or dry 
joints of L271, L273, C370, 
C386, R339 & L320 A
A
No
No Ye s
Ye s Ye s
No
NoYe sYe s
Ye s
No
Ye sNoNoYe sYe s
No
No
Check R245 for dry 
joint or faulty
No 
						

							FMR-2045A-2December 26, 2003
UHF Band 2 Theory of Operation: Transmitter 37
Chapter 4 UHF Band 2 Theory of Operation
4.1 Transmitter
Figure 4-1.  Transmitter Block Diagram
4.1.1 General
(Refer to Figure 4-1)
The UHF transmitter contains five basic circuits:
 power amplifier
 antenna switch
 harmonic filter
 antenna matching network
 power control integrated circuit (PCIC)
4.1.2 Power Amplifier
The power amplifier consists of two devices:
 9Z67 LDMOS driver IC (U101)
 PRF1507 LDMOS PA (Q110)
The 9Z67 LDMOS driver IC contains a 2 stage amplification with a supply voltage of 7.3V.
This RF power amplifier is capable of supplying an output power of 0.3W (pin 6 and 7) with an input 
signal of 2 mW (3 dBm) (pin16). The current drain would typically be 160 mA while operating in the 
frequency range of 450-527 MHz. 
The PRF1507 LDMOS PA is capable of supplying an output power of 7W with an input signal of 
0.3W. The current drain would typically be 1300 mA while operating in the frequency range of 
450-527 MHz. The power output can be varied by changing the biasing voltage.PCIC
Antenna
PA
Driver
VcontrolVcontrol
From VCO
 Jack
PA - F i n a l
StageAntenna Switch/
Harmonic Filter/
Matching Network 
						

							December 26, 2003FMR-2045A-2
38UHF Band 2 Theory of Operation: Transmitter
4.1.3 Antenna Switch
The antenna switch circuit consists of two PIN diodes (CR101 and CR102), a pi network (C107, 
L104 and C106), and two current limiting resistors (R101, R170). In the transmit mode, B+ at PCIC 
(U102) pin 23 will go low and turn on Q111 where a B+ bias is applied to the antenna switch circuit to 
bias the diodes on. The shunt diode (CR102) shorts out the receiver port, and the pi network, which 
operates as a quarter wave transmission line, transforms the low impedance of the shunt diode to a 
high impedance at the input of the harmonic filter. In the receive mode, the diodes are both off, and 
hence, there exists a low attenuation path between the antenna and receiver ports.
4.1.4 Harmonic Filter
The harmonic filter consists of C104, L102, C103, L101 and C102. The design of the harmonic filter 
for UHF is that of a modified Zolotarev design. It has been optimized for efficiency of the power 
module. This type of filter has the advantage that it can give a greater attenuation in the stop-band 
for a given ripple level. The harmonic filter insertion loss is typically less than 1.2 dB. 
4.1.5 Antenna Matching Network
A matching network which is made up of L116 is used to match the antenna’s impedance to the 
harmonic filter. This will optimize the performance of the transmitter and receiver into an antenna.
4.1.6 Power Control Integrated Circuit (PCIC)
The transmitter uses the Power Control IC (PCIC), U102 to regulate the power output of the radio. 
The current to the final stage of the power module is supplied through R101, which provides a 
voltage proportional to the current drain. This voltage is then fed back to the Automatic Level Control 
(ALC) within the PCIC to regulate the output power of the transmitter.
The PCIC has internal digital to analog converters (DACs) which provide the reference voltage of the 
control loop. The reference voltage level is programmable through the SPI line of the PCIC.
There are resistors and integrators within the PCIC, and external capacitors (C133, C134 and C135) 
in controlling the transmitter rising and falling time. These are necessary in reducing the power 
splatter into adjacent channels.
CR105 and its associated components are part of the temperature cut back circuitry. It senses the 
printed circuit board temperature around the transmitter circuits and output a DC voltage to the 
PCIC. If the DC voltage produced exceeds the set threshold in the PCIC, the transmitter output 
power will be reduced so as to reduce the transmitter temperature. 
						

							FMR-2045A-2December 26, 2003
UHF Band 2 Theory of Operation: Receiver39
4.2 Receiver
Figure 4-2.  UHF Receiver Block Diagram
4.2.1 Receiver Front-End
(Refer to “Figure 5-4. UHF Band 2 Receiver Front End Schematic Diagram” on page 50 and “Figure 
5-9. UHF Band 2 Transmitter Schematic Diagram” on page 55.
The RF signal is received by the antenna and applied to a low-pass filter. For UHF, the filter consists 
of L101, L102, C102, C103, C104. The filtered RF signal is passed through the antenna switch. The 
antenna switch circuit consists of two PIN diodes (CR101 and CR102) and a pi network (C106, L104 
and C107).The signal is then applied to a varactor tuned bandpass filter. The UHF bandpass filter 
comprises L301, L302, C302, C303, C304, CR301, and CR302. The bandpass filter is tuned by 
applying a control voltage to the varactor diodes (CR301 and CR302) in the filter.
The bandpass filter is electronically tuned by the DACRx from IC404, which is controlled by the 
microprocessor. Depending on the carrier frequency, the DACRx will supply the tuned voltage to the 
varactor diodes in the filter. Wideband operation of the filter is achieved by shifting the bandpass filter 
across the band.
The output of the bandpass filter is coupled to the RF amplifier transistor Q301 via C307. After being 
amplified by the RF amplifier, the RF signal is further filtered by a second varactor tuned bandpass 
filter, consisting of L306, L307, C313, C317, CR304, and CR305.
Both the pre- and post-RF amplifier varactor tuned filters have similar responses. The 3 dB 
bandwidth of the filter is about 50 MHz. This enables the filters to be electronically controlled by 
using a single control voltage which is DACRx.
Crystal 
Filter Mixer Va r a c t o r  
Tuned Filter RF Amp Va r a c t o r  
Tuned Filter Pin Diode 
Antenna 
Switch
RF Jack Antenna
Control Voltage
 from ASFICFirst LO
from VCO
Second LOIF Amp
455kHz
 Filter
Switch
455kHz
 Filter
455kHz
 FilterSwitch
Demodulator
RSSI
LimiterRecovered Audio
BW SELU301 
						

							December 26, 2003FMR-2045A-2
40UHF Band 2 Theory of Operation: Frequency Generation Circuitry
The output of the post-RF amplifier filter which is connected to the passive double balanced mixer 
consists of T301, T302, and CR306. Matching of the filter to the mixer is provided by C381. After 
mixing with the first LO signal from the voltage controlled oscillator (VCO) using low side injection, 
the RF signal is down-converted to the 44.85 MHz IF signal.
The IF signal coming out of the mixer is transferred to the crystal filter (FL301) through a resistor pad 
and a diplexer (C322 and L310). Matching to the input of the crystal filter is provided by C324 and 
L311. The crystal filter provides the necessary selectivity and intermodulation protection.
4.2.2 Receiver Back-End
(Refer to “Figure 5-5. UHF Band 2 Receiver Back End Schematic Diagram” on page 51.)
The output of crystal filter FL301 is matched to the input of first IF amplifier transistor Q302 by L330. 
Voltage supply to the IF amplifier is taken from the receive 5 volts (R5). The IF amplifier provides a 
gain of about 16 dB. The amplified first IF signal is then coupled into U301 (pin 1) via C360 and 
L332, which provides the matching for the first IF amplifier and U301.
Within U301, the first IF 44.85 MHz signal mixes with the 44.395 MHz second local oscillator (2nd 
LO) to produce the second IF signal at 455 kHz. The 2nd LO signal frequency is determined by 
crystal Y300. The second IF signal (455 kHz) is then filtered by an external ceramic filter FL302 
before being amplified by the second IF amplifier within U301. Again, the signal is filtered by a 
second external ceramic filter FL303 or FL304, depending on the selected channel spacing. FL303 is 
used for 20/25 kHz channel spacing whereas FL304 is used for 12.5 kHz channel spacing. The 
simple circuit consisting of U302, CR312, CR313 and resistors R345, R360, R321, and R324 divert 
the second IF signal according to the BW_SEL line. The filtered output of the second IF signal is 
applied to the limiter input pin of U301.
The IF IC (U301) contains a quadrature detector using a ceramic phase-shift element (Y301) to 
provide audio detection. Internal amplification provides an audio output level around 120 mVrms 
(@60% deviation) from pin 8 of U301. This demodulated audio is fed to the ASFIC_CMP IC (U404) 
in the controller section.
The IF IC (U301) also performs several other functions. It provides a received signal-strength 
indicator (RSSI) with a dynamic range of 70 dB. The RSSI is a DC voltage monitored by the 
microprocessor, and is used as a peak indicator during the bench tuning of the receiver front-end 
varactor filter.
4.3 Frequency Generation Circuitry
Figure 4-3.  Frequency Generation Unit Block Diagram
Voltage 
Multiplier
Synthesizer 
U201
Dual 
Tran-
sistor
Loop 
Filter
VCOBIC 
U241Low 
Pass 
Filter
Matching 
Network
Attenuator
To
Mixer
To
PA  D r i v e rVCP
Vmult1Aux3
Aux4
MOD Out
Modulating
Signal Vmult2Rx VCO Circuit
Tx VCO CircuitTRB
16.8 MHz
Ref. Osc.Rx Out
Tx Out