Tait TM8100 mobiles - Power Supplies

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 (+6V0)
■ Task 5: 5V DC supply following filtering of 6V supply (+5V DEC)
■ Task 6: 3V DC supply from 3V regulator in PSU module (+3V0 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
3V
SUPPLY
VCO
CIRCUITRY
FREQUENCY
SYNTHESIZER
INTERFACE
CIRCUITRY
INVERTER
JUNCTION OF
C531 AND R530
JUNCTION OF
C531 AND R530
+3V0 AN
L506
9V
SUPPLY
6V
SUPPLY
AGND
+9V0
+6V0
VCL SUPPLY+5V DEC