TROUBLESHOOTING: LO Output Test
RX Main VCO Test (Continued)
Is the
voltage between
0.5 and 2.1 Vdc
?
Check that the voltage
at C321 (pin 9) is between
0.5 and 2.1 Vdc.
Check that the TCXO oscillator
frequency is 33.6 MHz +
84 Hz.
There is no issue with
the control voltage.
Ensure the correct band select is
chosen. For 800 band, U300 pin 8/
C332 is low and pin 7/C331 is high.
For 900 band pin 7/C331 is low and
pin 8/C332 is high.
Check for a problem in
the TCXO oscillator
circuit. Refer to the
TCXO Oscillator
flowchart.
Check for a problem in the
VCO module. Replace the
module and test again.
Yes
No
Is
the voltage
railed low
(<0.5 Vdc)
?
Is the
TCXO frequency
within range
?
Is
the voltage railed
high (>2.1 Vdc)
?
No
Yes
No
Yes
Check for opens, shorts, or missing
components in the loop filter. Ensure SEL1
and SEL2 voltage levels are programmed
properly.Ensure SLEDGEHAMMER
commands are proper.
Continued
from previous
Page
No
‘
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