BW Broadcast technical manual
Page 30
Technical data
3.23 POWER AMPLIFIER BOARD
PSU interface
CON1 (70 Pin) provides the interface between the plugin power supply and the interface PCB, and supports the
main 50V output as well as the 12V auxiallary power, and all PSU control parameters. LED's D2 & D3 are used
to indicate AGC_OFF and AC_OK status. The high current inductor L1 and capacitor C1 smooth the main output
voltage, and the headers J1 & J2 set PS_ON and PS_Kill status.
Bus bar board
The busbar PCB is located onto the side face of the windtunnel and interfaces with the Fan control PCB and D to
IDC PCB through sub-minature D-type connectors, fixed in place with several hanks.The main voltage from the
PSU arrives at input of REG1 through the 36-pin EDGE connector. REG1 is a switching regulator. The 52kHz out-
put signal from REG1 is half rectified by D1 and smoothed out through L1, C2 and C3. The resulting DC voltage
is used to drive both the rear panel 80mm fans. R2 which is in the feedback loop of REG1, adjusts the maximum
voltage to accommodate different fan types and/or calibrate the fan speed. Part of the feedback loop includes a
temperature sensor TH (placed on the rear of the bus bar board), making the amount of airflow in the transmit-
ter temperature dependent through the fan speed adjustment. The LED D2 indicates there is an output voltage
present for the fans.
The 12V Auxillary output from the PSU is fed to a boost regulator REG2 through the 36-pin edge connector where
it is increased to 24V, half recitifed by D3 before being fed to the 18V regulator REG3 and out to the 10 Pin head-
er J3 to provide the power to the Combo board. C14, and C15 are used to smooth the 18V output from REG3.
Fan Connector Board
This PCB provides two independant 12V fan outputs via the screwless terminal connector CON1, and is filtered
by the two capacitors C1, and C2.
D to IDC Board
The 25 way D-type connector J2 interfaces with the 25 Way D-type J1 on the D to IDC PCB. Each pin on the
D-type is filtered individually with SMT capacitors C1-C25, with 10 pins running to the Controller Board and the
remaining 15 carrying the 50V line to power the dual Double Pallets.
PA Controller board
The controller board controls the power output of an output amplifier based on forward VSWR detection, reverse
VSWR detection, forward power signal from the LCD board and temperature. All op-amps are supplied with +18V
from the AUX power supply line, buffered by the capacitors C1, C2, C8 and C15.
Detected reverse VSWR (sniffed of the power amplifier's main RF output line) arrives through CON2 and input
filter C5-R7 to the IC2A. The gain of the op-amp is set by R22 and R23. Amplified signal is smoothed by C13 and
C14 and fed to the OR-ing circuit on the input of IC1B.
Detected forward VSWR (sniffed of the power amplifier's main RF output line) arrives through CON1 and input fil-
ter C7-R24 to the IC2B. The gain of the op-amp is set by R9, R10 and VR2. Amplified signal is smoothed by C12
and fed to the OR-ing circuit on the input of IC1B.
Forward power control signal comes from the micro controller on the LCD board to the inverting input of IC1A
through R4 and C10. A voltage divider R12 and R13 sets the voltage reference to the non-inverting input to be
half of the AUX power supply rail. The gain of the op-amp is set by R4 and R5. Output signal is fed directly to the
IC1B.
IC1B includes an OR-ing circuit on the input and a summer (R32-R34) to combine the reverse VSWR, forward
VSWR and PA control signals together. Output of IC1B is then a final control signal that controls the output of the
power amplifier by controlling it's power supply voltage. R27 and VR3 set the voltage reference to the inverting
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