9/15/06
888-2586-001
4-63
WARNING: Disconnect primary power prior to servicing.
Section 4 Overall System Theory
Platinum Z16HD+
4.8.7.1.7 Power Control: HDx-FM Exciter or BoostPro
The transmitter power output is determined by the RF drive to the PAs from the IPA
output. The IPA output level is controlled by the RF drive generated by the RF Source,
based on the signal APC which is an analog voltage (variable DC).
APC enters the Life Support board at J1-A35 from the Master Controller where it is
applied to analog switch, U5-1. If the Master Controller is working, then U5-13 is high
and APC passes through the switch to U5-4. If there is no mute signal present at U5-5,
the signal will pass through U1-7 and via the Display Backplane board becomes the
APC_IN control signal for the RF Source.
4.8.7.1.8 Power Control: Backup FM Mode (Analog Exciter)
Using the Backup FM (only) modulation format, 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) 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.
4.8.7.1.9 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_AB_I or IPA_CD_I Sample. This
is compared against IPA_AB_V or IPA_CD_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 (U21 and Q2 for IPA_CD) 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 for
IPA_AB (R51 and R52 for IPA_CD). This is sent to the Master Controller for
monitoring and protection.
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
Summary of Contents for Platinum Z16HD+
Page 4: ...MRH 2 888 2586 001 9 15 06 WARNING Disconnect primary power prior to servicing ...
Page 6: ...9 15 06 888 2586 001 MRH 1 WARNING Disconnect primary power prior to servicing ...
Page 8: ...viii 888 2586 001 9 15 06 WARNING Disconnect primary power prior to servicing ...
Page 10: ...x 888 2586 001 9 15 06 WARNING Disconnect primary power prior to servicing ...