VS1 Troubleshooting Manual
Detailed Circuit Descriptions
Issue 10.0 2018-10-29
Page 2-3
LVPS
Two +48 V to +5 V dc-dc converters (U2 and U12) and their associated components generate
the +5 V rail that is applied to circuitry throughout the transmitter.
A +48 V to +15 V converter (U1) and its associated components generate the +15 V that is
applied to the exciter/control PWB.
Pre-amp/IPA PWB (
NAPA28B
)
See electrical schematic Figure SD-4.
The pre-amp/IPA PWB (A5) accepts the RF output of the exciter/control PWB (A1), or
external source, and amplifies it to an intermediate RF drive level for application to the PA
PWBs (A6 through A9) via the splitter PWB (A4). The pre-amp/IPA PWB contains two N-
channel FETs (Q1 and Q2) and associated components configured as a two-stage RF power
amplifier. The RF output is generated by the
Pre-amp V
and
IPA V
levels provided by the PS
distribution PWB (A2), and the
Pre-amp Bias
and
IPA Bias
outputs from the exciter/control
PWB (A1). The RF output level is controlled by the RF input level generated by the exciter/
control PWB. Cooling air for the pre-amp PWB is provided by fan B1.
The
RF Drive
input is applied to the gate of FET Q1 through a series of micro-strip
transmission line sections and capacitors C1 and C2 and inductor L1, which provide
impedance matching to transform the 50 ohm input to low impedance for application to Q1.
Additional micro-strip transmission line sections at the output of Q1, as well as inductors L8
and L9 and capacitors C16 and C17, impedance match the Q1 output signal to 50 ohms. The
impedance matched output of Q1 is applied to the gate of FET Q2 through a series of micro-
strip transmission line sections and associated components, including capacitor C18 and
inductor L10, which provide impedance matching to transform the 50 ohm input to low
impedance for application to Q2. Additional micro-strip transmission line sections at the
output of Q2, as well as inductors L16 and L17 and capacitors C25 through C27, impedance
match the
RF Output
signal to 50 ohms.
The
Pre-amp V
input is applied to capacitors C29, C10, C11 and C12, which act as a broadband
decoupling network. Capacitor C15 and inductors L5 and L7 provide low-pass filtering of the
RF signal back to the ac-dc power stage.
The
IPA V
input is applied to capacitors C19, C21, C22 and C24, which act as a broadband
decoupling network. Capacitor C23 and inductors L14 and L15 provide low-pass filtering of
the RF signal back to the ac-dc power stage.
Summary of Contents for VS1
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Page 8: ...VS1 Troubleshooting Manual Page viii Issue 10 0 2018 10 29...
Page 56: ...VS1 Troubleshooting Manual Responding to alarms Page 1 48 Issue 10 0 2018 10 29...
Page 84: ...VS1 Troubleshooting Manual Wiring connector lists Page 4 6 Issue 10 0 2018 10 29...
Page 102: ...Issue 10 0 2018 10 29 MD 7 Figure MD 7 NAPA23 03A PA PWB C16 R13 R12 C5 C8...
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