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

							FMR-2045A-2December 26, 2003
UHF Band 2 Troubleshooting Charts: Troubleshooting Flow Chart for Controller 61
Chapter 6 UHF Band 2 Troubleshooting Charts
6.1 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 pro-
gram 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 
Troubleshoot-
ing 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 
AudioPA 
(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
62UHF Band 2 Troubleshooting Charts: Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)
6.2 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 Band 2 Troubleshooting Charts: Troubleshooting Flow Chart for Receiver (Sheet 2 of 2) 63
6.3 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
64UHF Band 2 Troubleshooting Charts: Troubleshooting Flow Chart for Transmitter
6.4 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 Band 2 Troubleshooting Charts: Troubleshooting Flow Chart for Synthesizer 65
6.5 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 47
AT = 13 VDC
Is U241 Pin 19
4.3 VDC in TX?
Start
Vi s u a l  
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
66UHF Band 2 Troubleshooting Charts: Troubleshooting Flow Chart for VCO
6.6 Troubleshooting 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 
						

							Chapter 7 VHF Theory of Operation
7.1 Transmitter
Figure 7-1.  Transmitter Block Diagram
7.1.1 General
(Refer to Figure 7-1.)
The VHF transmitter contains five basic circuits:
 Power amplifier 
 Antenna switch
 Harmonic filter
 Antenna matching network
 Power control integrated circuit (PCIC)
7.1.2 Power Amplifier
The power amplifier consists of two devices: 
 9Z67 LDMOS driver IC (U3501)
 PRF1507 LDMOS PA (Q3501)
The 9Z67 LDMOS driver IC contains a two-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 2mW (3 dBm) (pin16). The current drain would typically be 130mA while operating in the 
frequency range of 136-174 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 1800 mA while operating in the frequency range of 
136-174 MHz. The power output can be varied by changing the biasing voltage.PCIC
Antenna
PA
Driver
VcontrolVcontrol
From VCO
 Jack
Antenna Switch/
Harmonic Filter/
Matching Network PA
Final Stage 
						

							December 26, 2003FMR-2045A-2
68VHF Theory of Operation: Transmitter
7.1.3 Antenna Switch
The antenna switch circuit consists of two PIN diodes (D3521 and D3551), a pi network (C3531, 
L3551 and C3550), and three current limiting resistors (R3571, R3572, R3573). In the transmit 
mode, B+ at PCIC (U3502) pin 23 will go low and turn on Q3561 where a B+ bias is applied to the 
antenna switch circuit to bias the diodes “on.” The shunt diode (D3551) 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.
7.1.4 Harmonic Filter
The harmonic filter consists of C3532 to C3536, L3531 and L3532. This network forms a low-pass 
filter to attenuate harmonic energy of the transmitter to specifications level. The harmonic filter 
insertion loss should be less than 1.2 dB.
7.1.5 Antenna Matching Network
A matching network which is made up of L3538 and C3537 is used to match the antennas 
impedance to the harmonic filter. This will optimize the performance of the transmitter and receiver 
into an antenna.
7.1.6 Power Control Integrated Circuit (PCIC)
The transmitter uses the Power Control IC (PCIC), U3502 to control the power output of the radio by 
maintaining the radio current drain. The current to the final stage of the power module is supplied 
through R3519 (0.1ohms), 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 keep the whole loop stable. 
The PCIC has internal digital to analog converters (DACs) which provide the reference voltage of the 
control loop. The voltage level is controlled by the microprocessor through the data line of the PCIC.
There are resistors and integrators within the PCIC, and external capacitors (C3562, C3563 and 
C3565) in controlling the transmitter rising and falling time. These are necessary in reducing the 
power splatter into adjacent channels.
U3503 and its associated circuitry acts as a temperature cut back circuitry. This circuitry provides the 
necessary voltage to the PCIC to cut the transmitter power when the radio temperature gets too 
high. 
						

							FMR-2045A-2December 26, 2003
VHF Theory of Operation: Receiver69
7.2 Receiver
Figure 7-2.  VHF Receiver Block Diagram
7.2.1 Receiver Front-End
(Refer toVHF Receiver Front-End Schematic Diagram on page 80, VHF Receiver Back-End 
Schematic Diagram on page 81, and VHF Transmitter Schematic Diagram on page 84.)
The RF signal is received by the antenna and applied to a low-pass filter. For VHF, the filter consists 
of L3531, L3532, C3532 to C3563. The filtered RF signal is passed through the antenna switch. The 
antenna switch circuit consists of two PIN diodes (D3521 and D3551) and a pi network (C3531, 
L3551 and C3550).The signal is then applied to a varactor tuned bandpass filter. The VHF bandpass 
filter comprises of L3301, L3303, C3301 to C3304 and D3301. The bandpass filter is tuned by 
applying a control voltage to the varactor diode (D3301) 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 Q3302 via C3306. After 
being amplified by the RF amplifier, the RF signal is further filtered by a second varactor tuned 
bandpass filter, consisting of L3305, L3306, C3311 to C3314 and D3302. 
Both the pre and post-RF amplifier varactor tuned filters have similar responses. The 3 dB bandwidth 
of the filter is about 12 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 SELU3220 
						

							December 26, 2003FMR-2045A-2
70VHF Theory of Operation: Receiver
The output of the post-RF amplifier filter is connected to the passive double balanced mixer which 
consists of T3301, T3302 and CR3301. Matching of the filter to the mixer is provided by C3317, 
C3318 and L3308. After mixing with the first LO signal from the voltage controlled oscillator (VCO) 
using high 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 (Y3200) through a resistor pad 
(R3321 - R3323) and a diplexer (C3320 and L3309). Matching to the input of the crystal filter is 
provided by C3201 and L3200. The crystal filter provides the necessary selectivity and 
intermodulation protection. 
7.2.2 Receiver Back-End
(Refer to VHF Receiver Back-End Schematic Diagram on page 81.)
The output of crystal filter Y3200 is matched to the input of IF amplifier transistor Q3200 by L3203. 
Voltage supply to the IF amplifier is taken from the receive 5 volts (R5). The IF amplifier Q3200 is 
actively biased by a collector base feedback provided by R3202 and R3203. The gain controlled IF 
amplifer provides a maximum gain of about 16dB. A dual hot carrier diode (CR3201) limits the filter 
output voltage swing to reduce overdrive effects at RF levels above -27dBm. The amplified IF signal 
is then coupled into U3220 (pin 1) via L3202, C3207, and C3200 which provides the matching for the 
IF amplifier and U3220.
The IF signal applied to pin 1 of U3220 is amplified, down-converted, filtered, and demodulated, to 
produce the recovered audio at pin 7 of U3220.
Within U3220, 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 Y3201. The second IF signal (455 kHz) is then filtered by an external ceramic filter Y3205 
before being amplified by the second IF amplifier within U3220. Again, the signal is filtered by a 
second external ceramic filter Y3203 or Y3204 depending on the selected channel spacing. Y3203 is 
used for 20/25 kHz channel spacing whereas Y3204, for 12.5 kHz channel spacing. The simple 
circuit consisting of U3221, CR3202, CR3203 and resistors R3209, R3212, R3211 and R3205 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 U3220 (Pin 14). 
The IF IC (U3220) contains a quadrature detector using a ceramic phase-shift element (Y3202) to 
provide audio detection. Internal amplification provides an audio output level around 120mVrms 
(@60% deviation) from pin 8 of U3220. This demodulated audio is fed to the ASFIC_CMP IC (U404) 
in the controller section.
The IF IC (U3220) 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 used as a peak indicator during the bench tuning of the receiver front-end 
varactor filter.
7.2.3 Automatic Gain Control Circuit
(Refer to VHF Receiver Front-End Schematic Diagram on page 80 and VHF Receiver Back-End 
Schematic Diagram on page 81.)
The front-end automatic gain control circuit provides automatic reduction of gain, of the front-end RF 
amplifier via feedback. This action is necessary to prevent overloading of back-end circuits. This is 
achieved by drawing some of the output power from the RF amplifier output. At high radio 
frequencies, capacitor C3327 provides the low impedance path to ground for this purpose. CR3302 
is a PIN diode used for switching the path on or off. A certain amount of forward biasing current is 
needed to turn the PIN diode on. Transistor Q3301 provides this current.