Motorola i425e Detailed Service Manual page 69

RX Main VCO Test (Continued)
Continued
from previous
Page
Check that the voltage
at R603 is between
0.5 and 2.1 Vdc.
Is the
voltage between
0.5 and 2.1 Vdc
?
Pass
Check that the TCXO oscillator
frequency is 33.6 MHz +84 Hz.
Ensure the correct band select is chosen.
For 800 band, U300 pin 8/C302 is low and
pin 7/C304 is high. For 900 band U300 pin
7/C304 is low and pin 8/C302 is high.
Is the
TCXO frequency
within range
?
Pass
Check for a problem in the
VCO module. Replace the
module and test again.
6880401P26-O
Is
Fail
the voltage railed
high (>2.1 Vdc)
?
Check for opens, shorts, or missing
components in the loop filter. Ensure SEL1
and SEL2 voltage levels are programmed
properly.Ensure SLEDGEHAMMER
Check for a problem in
the TCXO oscillator
Fail
circuit. Refer to the
TCXO Oscillator
flowchart.
TROUBLESHOOTING: RX Main VCO Test
There is no issue with
the control voltage.
Is
the voltage
Fail
railed low
(<0.5 Vdc)
?
Pass
Correct band is
selected.
commands are proper.
Fail
69