User's Manual

2650 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions
435B, Rev. 0 4-28
The +28 VDC output of the switching
power supply assembly connects to (A8)
the Current Metering Board.
4.2.11 (A8) Current Metering Board
(1301316; Appendix D)
The Current Metering Board distributes
the voltages through fuses to the
Amplifier Devices on the Filter/Amplifier,
High Band Driver Board, the High Band
Amplifier Board and the three Final High
Band Amplifier Boards. The Fuses F1, F2
& F3 are 15 Amp, F4 is 5 Amp, F6 is 2
Amp and F7 is 1 Amp Fuse. F5 is not
used in this configuration. There are two
Spare Fuses, one 1 Amp and one 15
Amp, located on the top, right rear of the
Tray.
Fuse F1 protects (A4-A1) the High Band
Output Amplifier Pallet, Fuse F2 protects
(A4-A2) the High Band Output Amplifier
Pallet, Fuse F3 protects (A4-A3) the High
Band Output Amplifier Pallet, Fuse F4
protects (A3-A2) the High Band Amplifier
Pallet, and Fuse F6 protects (A2-A1) the
Filter/Amplifier Board. Fuse F7 supplies
+28 VDC to J8 Pin 2 on the AGC Control
Board. The +28 VDC is connected to the
Regulator IC U7 that takes the +28 VDC
and provides a +12 VDC output.
The +12 VDC is used for operation of the
AGC Control Board and also the +12 VDC
is connected through the Current
Metering Board, jumper from TB1-5 to
TB1-6, to the Phase Shifter Board, the
Filter/Amplifier Board and the Overdrive
Protection Board. The Current Metering
Board also supplies sample outputs of the
operating currents of the amplifier
devices in the Tray to the front panel
Current Meter.
The Meter in the (I
1
) position reads the
current for the (A4-A1) P400 High Band
Output Amplifier Board, (I
2
) for the (A4-
A2) P400 High Band Output Amplifier
Board and (I
3
) for the (A4-A3) P400 High
Band Output Amplifier Board. The (I
D
)
position reads the current for the (A3-A2)
P200 High Band Amplifier Board. To read
the desired current, Switch S2 to the
proper position checking that S1 is in the
Current position. These current readings
can be used when setting up the Idling
Currents, no RF Drive applied, for the
devices. (I
1
, I
2
& I
3
) are set for 6 Amps
max. I
D
is set for 3 Amps max. (NOTE:
All front panel current readings must be
multiplied by 2 for the proper readings.)
4.2.12 Operation of the VHF
Amplifier Tray
The 220 VAC from the AC distribution
panel is applied through Jack J4 to
Terminal Block TB1 in the Tray. When
(CB1) the 15 Amp rear panel mounted
AC Circuit Breaker is switched On, the
220 VAC is distributed from TB1 to (A11
& A12) two cooling Fans, which will
operate, and to (A10) the Switching
Power Supply. There are two Surge
Suppressors, VR1 and VR2, mounted on
TB1 that provide protection from
transients or surges on the input AC Line.
There are two Surge Suppressors, VR3
and VR4, mounted at the input to the
switching power supply from each AC
Line to ground, which also provide
protection from transients or surges on
the AC Line.
The switching power Supply only
operates when the Power Supply Enable
Control Line, Jack (J3 Pins 9 & 10),
located on the rear of the Tray, are
shorted. The Enable is generated by the
VHF exciter tray when the transmitter is
switched to Operate. The Enable is
applied to (A13) the AGC Control Board
(1142-1601), which, if there is no
Thermal Fault, connects the Enable from
J10 Pins 6 & 7 to J2-6 & 4 on the
Switching Power Supply Assembly. The
Green Enable Front Panel LED (DS2) will
light, indicating an Enable is present. If
the Amplifier Array is in Standby or if a
Thermal Fault occurs, the AGC Control
Board will not Enable the Switching
Power Supply, therefore the +28 VDC will
be removed from the Amplifier Modules
and the Front Panel Enable LED and
Module Status LEDs will be out.