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WARNING: Disconnect primary power prior to servicing.
Overall System Theory
•
The low from K2-4 goes off the board to the IPA Backplane Board where it actu-
ates the IPA select relays, K2 and K3 to the position shown on the schematic. It
also goes to the Master Controller as a status signal, so it knows which IPA is
selected.
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IPA 2 is selected when IPA_SELECT_AB2 goes high which will SET K2. K2-4
will go high and this will switch K2 and K3 on the IPA Backplane board to the
IPA 2 position. K2 is also responsible for switching the IPA gate control voltage
(transmitter power control signal) to the active IPA.
4.7.6.1.7 Power Control
The transmitter power output is controlled by the IPA output level. The IPA output
level is controlled by the signal MSTR_IPA_CTL, which is an analog voltage
(variable DC), from the APC loop circuitry on the Master Controller, which will
control the IPA gate voltage. Varying the gate voltage will vary the IPA power
output. MSTR_IPA_CTL, enters the board at J1-A35 where it is applied to analog
switch, U5-1. If the Master Controller is working, then U5-13 is high and
MSTR_IPA_CTL passes through the switch to U5-4. If there is no mute signal
present at U5-5, the signal will pass through to CR4 and U15-3. CR4 and R30
basically create a negative gate bias for the IPA which will vary with the
MSTR_IPA_CTL signal. The IPA requires about -15V to be completely shut off and
about 0V to be fully turned on. For more information on Power Control refer to the
APC discussion earlier in this section under the Master Controller.
4.7.6.1.8 IPA Current and Voltage Samples
IPA current is detected as the differential voltage across a current shunt resistor in
series with the IPA supply voltage on each IPA Backplane Board. The shunt resistor
is R1 on the IPA Backplane. The current sample is called IPA_I Sample. This is
compared against IPA_V Sample, which comes from the input side of the shunt
resistor. The voltage difference between these to samples is directly proportional to
the current flowing through the shunt resistor. The difference is amplified by U18-6
and Q1 and is sent to the Master Controller for monitoring and protection.
The IPA Voltage sample is taken from the voltage divider made up of R45 and R48.
This is sent to the Master Controller for monitoring and protection.
4.7.6.1.8.1 U18 Supply Voltage
The supply voltage for U18, VDP1 and VDN1 comes from U22 and diodes CR16,
CR17 and CR6. The Supply for U21 is VDP2 and VDN2. The samples coming into
U18 and U21 pins 2 and 3 are about 52 VDC. The supply voltage for U18 is floating
at VDP which is the PA voltage plus 4 volts and VDN which is the PA voltage
minus 4 volts. Basically U22 is a small switching supply providing a fl/-
supply for the op-amps U18 and U21.
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Страница 20: ...1 6 888 2406 002 WARNING Disconnect primary power prior to servicing Introduction Specifications ...
Страница 70: ...3 14 888 2406 002 WARNING Disconnect primary power prior to servicing Operator Guide ...
Страница 130: ...4 60 888 2406 002 WARNING Disconnect primary power prior to servicing Overall System Theory ...
Страница 156: ...5 26 888 2406 002 WARNING Disconnect primary power prior to servicing Maintenance and Alignment ...
Страница 194: ...6 38 888 2406 002 WARNING Disconnect primary power prior to servicing Troubleshooting ...
Страница 196: ...7 2 888 2406 002 WARNING Disconnect primary power prior to servicing Parts List ...