Specifications

compartments. If a cable is disconnected, the relays on the board
might not be in the correct position.
NOTE
The Driver Section has only 2 Efficiency Coil boards.
R.5.27.1
Closed Loop
A single +24VDC supply leaves the Frequency Control Interface
board and loops through all connections, and eventually returns
back to the input of a comparator. If all connections are made,
the voltage at the (+) input will be greater than the (-) inputs. The
output is logic high, which is the normal condition.
R.5.27.2 Open Loop
If any of the connections are open, the output of the comparator
will go logic low. This will generate a logic low Bandswitch Fault
via U16 and illuminate appropriate indicator of DS10 RED. An
RF MUTE will be applied to the transmitter and the front panel
Bandswitch Fault LED will be illuminated RED on the Fre-
quency Control Panel.
R.5.28
Band Fault Detectors
The same basic circuit is duplicated for the Predriver connector
J1, Driver connector J2, 2L1/2C2 connector J7, and 2C3/2C4
connector J10. When any one is disconnected, the appropriate
indicator of DS10 and the Bandswitch Fault indicators will be
illuminated RED.
R.5.29
VSWR PAL
The VSWR PAL receives the Band Data and encodes the active
high outputs for the Antenna and Network VSWR Detectors on
the Output Monitor at J15. For the Antenna VSWR output, the
PAL uses the External Adjustment BCD input and converts it to
a binary output. Each output is a 5 bit system.
R.5.30
RF Samples Interface
The Synthesizer Sync, Buffer, Predriver, and Driver voltage
samples are connected to Multimeter Selector Switch on the
Frequency Control board at J20.
R.5.31
Bandswitch Indicators
DS11 may be used to check the output levels of the relay drivers.
To use, simply connect the five conductor cable from J51 to any
of the J52 through J56 connectors. If the output is 0VDC,
meaning the relay should be energized, the indicator will be
illuminated RED.
NOTE
Depending upon the particular connector, the indicators may
monitor different bit outputs.
R.5.32 Power Distribution
R.5.32.1 +24VDC
The +24VDC supply input is fused by F1 through F7 and
connected to the all of the relays and interlock circuits.
R.5.32.2 +15VDC
The +15VDC supply is connected to the Tune Load raise/lower
control switches on the Frequency Control board at J13.
R.6 Troubleshooting
Circuitry on this board can be classified into these major areas:
a. Power Supply
b. Bandswitching
c. Tune Mode Control
d. Faults
e. Servo Control
R.6.1
Power Supply
When a PowerSupply fault is displayed on the Frequency control
front panel, then with only the low voltage on, check the LED
indicators on the board:
a. DS5 (+5V)
b. DS4 (-15V)
c. DS6 (+15V)
Each of these LED indicators should be illuminated, if the
individual supplies are operating normally.
a. If DS3 is illuminated RED:
b. Use a multimeter to measure the +15VDC, +5VDC, and -
15VDC power supplies.
c. If any supply has been reduced to less than 80% of normal:
1. Check the input fuse and replace if necessary.
2. If fuse is not open, measure input TP for the unregulated
voltage.
3. If the unregulated input is correct, replace the regulator.
d. If all supplies measure correct:
1. Check TP29 for +5VDC and replace U38 if necessary.
2. If TP29 is okay, measure the voltageson the comparator
inputs and outputs to determine if the comparator is
faulty.
R.6.2
Bandswitching
NOTE
If a failure has occurred in a bandswitching circuit, it is possible
to bypass the problem. Refer to the Emergency Operating Proce-
dures for more information.
R.6.2.1 Band Latch
a. Check the inputs/outputs of the Band Latch when switch-
ing from Low Power Tune to the Frequency Change mode.
b. Verify the 100ms output pulse.
1. If not correct, check the Band Latch clock input, verify
U15-5 is logic high and has the 12.5Hz clock input.
2. If not correct, replace Band Latch, U15, or U21 if
needed.
R.6.2.2 Encoder PALs
a. Check the Encoder outputs at a given frequency.
b. Use the Encoding Examples to determine the logic levels
out of the PAL.
1. Check the PAL inputs.
2. Use the Band Indicator jumper to check the output
status of the PAL
3. Replace the PAL if needed.
888-2339-002 R-9
WARNING: Disconnect primary power prior to servicing.