Specifications

1. If logic low, check U7-2. If also logic low check tran-
sistors and capacitors connected to the input.
2. If logic high, replace the PAL.
b. If D0 is a logic high, then check the output at J1 for a
-1.4VDC.
1. If J1 is +2.2VDC, replace the inverter driver.
c. If Drivers D1 through D6 are not being turned on, check
the D1 thorough D6 outputs of the PAL for a logic high.
1. If any outputs are logic low, replace the PAL.
d. If D0 is a logic high, then check the output at J1 for a
-1.4VDC.
1. If J1 is +2.2VDC, replace the inverter driver.
E.7.3.3 Drivers D7 - D14 Will Not Turn On
If any or all of the Drivers will not turn on, begin troubleshooting
as follows.
a. Place the Driver Test Jumper JP9 in the TEST position.
b. Measure the D7 through D14 outputs of the PAL.
1. If the outputs are not all logic high, replace the PAL.
c. If the outputs are all high, measure the outputs of the
inverter.
1. All outputs at J1 should be -1.4VDC, if any one is not,
replace the inverter driver.
2. If the negative voltages are present, inspect connector
J2 and refer to the Driver Combiner Troubleshooting
section to continue.
d. Measure the AGC inputs to the PAL. With the transmitter
OFF, all inputs should be logic high. If they are not, replace
U14 and U20.
e. Return the Driver Test Jumper back to the Normal position.
f. Measure the TX On Enable during the step-start sequence.
1. This input at J3 should go logic high when the transmit-
ter is turned on. If it does not, refer to the overall wiring
diagram and the Transmitter Interface Section as
needed.
E.7.3.4 Cable Interlock
If DS8 is illuminated RED on the Driver Encoder, there are three
basic possibilities,
a. Startby ensuring that the RF modules and cables are firmly
inserted into the Driver Encoder and Driver Combiner
Motherboard.
b. If the fault remains use a clip lead to jumper the cathode
of CR20 to R177 (J2-20 to J2-9).
1. If the LED extinguishes, refer to the Overall wiring
diagram and the Driver Combiner section to trace the
open.
c. If the LED is still illuminated, use another clip lead and
jumper R180 to the cathode of CR25 (J1-19 and J1-10).
1. If DS7 goes out refer to the Overall wiring diagram and
the Driver Combiner Section to trace the open.
d. If the LED remains illuminated when both clip leads are
in place, measure the voltages at the (+) input and (-) inputs
to the comparators.
1. If the (+) input voltage is greater than the (-) input,
replace the comparator.
2. If the (+) input voltage is less than the (-) input, check
the resistors and diodes.
e. If the output at J3 is logic high, refer to the overall wiring
diagram and the Transmitter Interface schematic section to
locate the fault.
E.7.4
A/D Phasing
a. Check for a carrier frequency or 1/2 carrier frequency
squarewave signal at TP4 of 5Vp-p when the transmitter is
on.
1. If not present, check JP8-2. If a carrier frequency signal
is present check the divider and the tri-state buffer.
b. If a carrier frequency signal is not present JP8-2, check for
a carrier frequency squarewave signal at the input of U18
of 0.7V to 4.3 Volts peak to peak when the transmitter is
on. If a signal is present, replace U18.
1. If not present at the U18 input, check the input circuitry.
There should be an RF signal detected across the input
resistor.
2. If there is no signal present, refer to the overall wiring
diagram to find the loss of signal from the RF Splitter.
c. If the correct output at TP4 is present, refer to the overall
wiring diagram and the A/D Converter Troubleshooting
section to continue.
E.8 Removal and Replacement
With the low voltage power supplies shut off, remove all connec-
tors and top outside mounting screws. The cable connectors are
keyed for identification during replacement. When installing the
replacement board, reverse the above procedure. Ensure that all
jumpers and switches on the new board are set to the same
position as corresponding ones on the original board.
E.9 Alignments
E.9.1 High & Low Drive Thresholds
Measure the voltage on TP5, High Drive, and adjust R5 to the
same as the recorded value from the factory test data sheet.
Measure the voltage on TP6, Low Drive with the transmitter on,
and adjust R6 to the same as the recorded value from the factory
test data sheet.
NOTE
If the transmitter turns OFF, due to a Low Drive Fault, turn R6
CW clock-wise 1 turn and repeat the adjustment.
E.9.2 AGC
Turn on the transmitter and observe the Relative RF Drive on the
front panel meter. Adjust R100 for the same reading as obtained
from the factory test data sheet for the specified frequency.
888-2339-002 E-9
WARNING: Disconnect primary power prior to servicing.