Specifications
Section F
RF Combiner Motherboards (A10-A19)
F.1 Introduction
This section describes the Main and Binary RF Combiner Moth-
erboards. Topics include function, location, detailed circuit de-
scription, and removal/replacement.
NOTE: For more information about the RF Combiner, refer to
the Overall System Theory Section.
NOTE: Parts List for this board is covered in Section VII, and
RF Amplifiers are described in Section G.
F.2 Function
The purpose of the Main RF Combiner Motherboards is to
provide the input/output connections for the Big Step RF Ampli-
fiers.
The purpose of the Binary RF Combiner Motherboard is to
provide the input/output connections for 12 Big Step RF Ampli-
fiers, and 4 Binary RF Amplifiers.
F.3 Location
The A10 Binary RF Combiner Motherboard and the A11 Main
RF Combiner Motherboard are located in the right compartment.
(SEE VIEW 15).
The A12 through A15 Main RF Combiner Motherboards are
located in the center compartment. (SEE VIEW 16).
The A16 through A19 Main RF Combiner Motherboards are
located in the left compartment. (SEE VIEW 17).
F.4 Detailed Circuit Description - Main
RF Combiner Motherboard
Refer to the Main Combiner Motherboard Schematic Diagram
(drawing 839-7930-002) for the following description.
Each Main RF Combiner Motherboard contains combiner trans-
former toroids (T1 through T16 on each board) and a printed
circuit board socket for 16 RF Amplifiers. The RF Amplifiers are
mounted in two rows of 8 connectors.
F.4.1
Big Step RF Amplifier Connections - J1
through J16
F.4.1.1 RF Input
The RF drive inputs are obtained from the A6 RF Splitter
secondary and the RF drive cables that are connected to J17
through J24. There is a separate RF drive cable for each half-
quad, so there are two separate RF drivecables for each amplifier.
All RF drive coaxial cables are the same length, so all RF drive
signals are in phase. Each RF Amplifier is provided two equal
amplitude and phase RF drive inputs at pins 49 and 53 of each
RF Driver connector.
F.4.1.2 Power Supply
Four fused +230VDC lines from the RF Amp Power Supply
enters the Main RF Combiner Motherboard at E1 through E4. It
is connected to each RF Amplifier connector at pin 23 and 29,
and can not be adjusted.
F.4.1.3 RF Output
Each RF Amplifier output is connected to one of the combiner
toriods (T1 through T16) at pins 1 and 7. Each of the toroids has
a turns ratio of 16:1, sixteen turns for the primary winding and
one turn for the secondary. The Efficiency Coil boards plug into
P1 through P8 on the Main RF Combiner Motherboard and their
taps are frequency determined.
F.4.1.4 Modulation Encoder Connections - J25 through J28
F.4.1.4.1 Turn-On Control Signals
On each of the four Modulation Encoder connectors, pins 1, 3,
5, and 7 are connected to pin 45 on four RF Amplifier connectors.
When the voltage is -2VDC on a pin, the RF Amplifier is turned
on.
F.4.1.4.2 Cable Interlock
When an amplifier is properly inserted a connection is made
between pins 35/36 and pins 37/38 on the amplifier connector.
On each of the four Modulation Encoder connectors, pin 9 will
loop- through connecting traces/amplifiers/connectors and re-
turn to pin 10 with very low resistance. If an amplifier is discon-
nected, pin 9 and pin 10 will be an open circuit.
F.5 Detailed Circuit Description - Bi-
nary RF Combiner Motherboard
Refer to the Binary RF Combiner Motherboard Schematic Dia-
gram (drawing 839-7930-003) for the following description.
The Binary RF Combiner Motherboard is similar to the Main
Combiner Motherboard, with some additional components and
differences.
F.5.1
Binary RF Amplifier Connections J1 through J4
F.5.1.1 Power Supply
TheB91/2StepandB101/4Stepoperatefrom+115VDCthat
enters at E5. The B11 1/8 Step and B12 1/16 Step operate from
+60VDC that enters at E1.
NOTE: +230VDC is connected to E2 and loops through E7/E8
and E9/E10 to supply the other four RF Amplifiers.
F.5.1.2 RF Output
The Binary Steps employ tapped transformer primary windings
for fine adjustments. The tap positions depend on operating
frequency and are selected with P30, P31, P32, and P33.
888-2339-002 F-1
WARNING: Disconnect primary power prior to servicing.