Tait TM8100 mobiles, Service Manual

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TM8100/TM8200 Service Manual Frequency Synthesizer Fault Finding 189
© Tait Electronics Limited November 2007
7. If the lock status is
110
, the second LO is out of lock. Go to
“Receiver Fault Finding” on page 247 .
8. If the lock status is
111
, this implies normal operation. But if the lock
error persists, replace the board and go to “Final Tasks” on page 163 .
9.2 Power Supplies
Introduction
First check that a power supply is not the cause of the fault. There are four
power supplies for the frequency synthesizer — two are supplied from the
PSU (power supply unit) module and two are produced in the synthesizer
circuitry itself:
■
Task 3 : 14VDC (K5 band: 15.5V) supply from SMPS (
VCL SUPPLY
)
■
Task 4 : 6V DC supply from 6V regulator in PSU module (
+6
V
0
)
■
Task 5 : 5V DC supply following filtering of 6V supply (
+5
V DEC
)
■
Task 6 : 3V DC supply from 3V regulator in PSU module (
+3
V
0
AN
).
The measurement points for diagnosing faults in the power supplies are
summarized in
Figure 9.1 .
Figure 9.1 Measurement points for the frequency synthesizer power supply circuitry
PIN 4 OF
Q508
PIN 4 OF
Q508
PIN 4 OF
IC606
PIN 4 OF
IC606
PIN 5 OF
IC606
PIN 5 OF
IC606
Q500 AND
R533
Q500 AND
R533
PINS 7 AND 15
OF IC503
PINS 7 AND 15
OF IC503
SIGNAL TYPES
RF
ANALOG
CLOCK
DIGITAL
PLL
14 V/15.5 V
SMPS
LOOP
FILTER
AND
SUMMER
FILTERING
OF SUPPLY
FOR PLL
AND LOOP
FILTER
FILTERING
OF SUPPLY
FOR VCO
CIRCUITRY
3 V
SUPPLY
VCO
CIRCUITRY
FREQUENCY
SYNTHESIZER
INTERFACE
CIRCUITRY
INVERTER
JUNCTION OF
C531 AND R530
JUNCTION OF
C531 AND R530
+3V0 AN
L506
9 V
SUPPLY
6 V
SUPPLY
AGND
+9V0
+6V0
VCL SUPPLY +5V DEC