Specifications

When TP11 goes low and U2-9 goes to +2.6VDC, the output of
U2-14 goes LOW and TP6 is a logic low. A Synthesizer Fault-L
is generated and sent to the Controller via the Transmitter Inter-
face.
Diode CR8 pulls up U2-11 to the +10VDC supply, so a fault can
not be generated by U2-13 (Synthesizer Interface B Fault).
B.6.4.2 Synthesizer Interface B Selected
K1 is energized and 0VDC is applied to U2-8 to prevent U2-14
(Synthesizer Interface A Fault) from going logic low. Diode CR8
is reversed biased, and the voltage at U2-10 is set at +4.6VDC
by R13 and R8. Should Synthesizer Interface B fail, U2-11 goes
to +2.6VDC and U2-13 goes to a logic low, generating a Synthe-
sizer Fault-L to the Controller via the Transmitter Interface.
B.6.5
VSWR Control Line
If the Output Monitor generates a VSWR-H signal, a logic high
appears at J11-5 and TP16 for 250nS. This voltage is distributed
to Synthesizer Interface A at J12-5 and optional Synthesizer
Interface B at J10-5 for SYNC switching.
B.6.6
Power Supplies
+22VDC passes through F1 and is regulated down to +15VDC
by U4. U3 is connected to the +15VDC and forms a +5VDC
supply. Indicators DS2 and DS1 illuminate GREEN when the
respective supplies are operational.
B.7 RF Interface Troubleshooting
Problems on this board can be classified into three areas. These
are:
a. Power Supply
b. Signal Switching, and
c. Fault Sensing.
Refer to the RF Interface Schematic (839-7930-515) as needed
for this section. Troubleshooting the circuitry associated with the
combined transmitter mode is covered in the combined transmit-
ter manual.
B.7.1
Power Supply
Begin troubleshooting by:
a. Checking that the +15VDC (DS2) and +5VDC (DS1)
LED’s are lit with the low voltage on only.
b. If DS1 is out but DS2 is lit:
1. Check TP1 for +5VDC.
2. If not present, check U3, and associated circuitry.
c. If both indicators are out:
1. Check F1, and replace if open.
2. If F1 is not open, then check for +22VDC on J1-1 and
-22 VDC on J1-3.
3. If not present, refer to the Transmitter Troubleshooting
section to troubleshoot the Low Voltage Supply.
4. If +22VDC is present, check TP2 for +15VDC.
5. If not present, check U4 and associated circuitry.
After repairs are made to the Power Supply, check the output of
the supplies to ground with an ohmmeter for shorts before
applying power to the board.
B.7.2
Signal Switching
If the transmitter will not switch between Synthesizer Interface
A and Synthesizer Interface B and/or there is no signal at TP5
(RF Out), the Synthesizer Interface Select Circuit may have
failed.
Note
If remotely switched to Synthesizer Interface B, local control will
have no effect.
a. Toggle the Synthesizer Select Switch (S2).
1. The Synthesizer Selected indicator (DS3 or DS4)
should light and extinguish as the switch is activated
and relay K1 should change states.
2. If no indicator lightsand K1 does not change states, then
check TP3 for +22VDC.
3. If not present, refer to the Transmitter troubleshooting
section for troubleshooting the Low Voltage Supplies.
b. If the indicators switch and K1 changes state but there is
no signal at TP5, check for the presence of RF at the
contacts of K1. Pins 2 and 6 are the input to the relay and
pin 10 is the output.
1. If there is no input check the connector associated with
the selected Synthesizer Interface for a signal.
2. If not present, refer to the Troubleshooting section of
the Synthesizer Interface and/or check cable for an open
or short.
c. If the input is present, but there is no output at pin 10,
disconnect J7 on the board.
1. If the signal returns, refer to the Troubleshooting sec-
tion of the Driver Combiner Motherboard and/or check
the cable for a short.
2. If the signal is still not present, replace K1.
d. If DS3 indicator remains on and K1 does not change states
when S2 is toggled, check the cathode of CR2 for
+12VDC.
1. If not present, check CR1, CR6 and F1.
2. If the +12VDC is present, check for +8 Volt on the
anode of CR2 when Synthesizer Interface A is selected
and 0VDC when Synthesizer Interface B is selected.
3. If the voltage changes but no action is seen on K1 or the
LED’s fail to switch, replace K1.
4. If voltage on the anode of CR2 does not change from
+8Volts,verifylowresistancetogroundwhenS2isin
the B position.
5. If no change is seen in resistance, replace S2.
e. If DS4 is lit and the voltage at the anode of CR2 remains
at 0VDC, verify that the Remote RF Select line from the
Transmitter Interface board is not active (High), to be sure
888-2339-002 B-3
Warning: Disconnect primary power prior to servicing.