output is not sufficient. Refer to SECTION A, Oscillator, for
additional information.
6.20
ColorStat™ panel Buffer Fault
If the transmitter is incurring Underdrive faults, and the Color-
Stat™ panel Buffer LED is illuminated RED, the Buffer Am-
plifier output is not sufficient. Refer to SECTION B, Buffer
Amplifier, for additional information.
6.21
ColorStat™ panel Predriver Fault
If the transmitter is incurring Underdrive faults, and the Pre-
driver ColorStat™ panel LED is illuminated RED during PA
Supply turn on, the Predriver output is not sufficient. Refer to
SECTION C, RF Amplifier, and SECTION D, Driver Com-
biner/Motherboard, for additional information.
6.22
ColorStat™ panel RF Amp Fault
The function of the RF AMP fault indicator is to alert the
operator that an RF amplifier has a blown fuse. This normally
indicates shorted MOSFET transistors on the PA Module. This
circuit only illuminates the RED LED on the ColorStat™ panel
and triggers a remote output if connected. The transmitter will
continue to operate normally, with slightly reduced power
and/or slightly increased distortion, depending on which ampli-
fier has failed.
In brief, this circuit mimics the RF amplifier blown fuse indica-
tors on each PA Module. The LED will illuminate RED at a
steady state or flash to the modulation or program level depend-
ing on which step has a blown fuse.
NOTE
Whenever all fuses on A24 and A25 are removed, the RF Amp
Fault will illuminate whenever the PA Power Supply is ener-
gized or P1 on the DC Regulator is in the TEST position. This is
normal.
6.23
ColorStat™ panel Analog Input
Board: +15V and -15V Supply Faults
If either the +15V or -15V Fault LED’s on the ColorStat™ panel
are RED, this indicates that the supply has failed. The transmit-
ter will generate a PA Turn-Off command and no power will be
produced. With the low voltage on, measure the voltage at both
ends of F2 on the Analog Input Board and verify that it is
approxi22 VDC. Measure the voltage on both sides of
F3 and verify that it is -22 VDC. If one fuse has failed, replace
the fuse and try again. If the fuse fails again, troubleshoot the
regulator circuit. Refer to SECTION J, Analog Input Board, and
SECTION M, DC Regulator, for additional information.
NOTE
It is sometimes possible for the regulator circuit to lock into a
fault condition if the output is accidentally shorted. If this oc-
curs, turn off the Low Voltage at CB1 and CB2 for approxi-
mately 1 minute to allow the power supply to discharge. Reap-
ply Low Voltage and note if the regulator is now reset.
6.24
ColorStat™ panel Analog to Digital
Converter
6.24.1
+15V, -15V, and +5V Supply Faults
If any of the Analog to Digital Converter LED’s (+15V, -15V,
or +5V) are RED on the ColorStat™ panel, this indicates that
the Supply has failed. The transmitter will generate a PA Turn-
Off command so no power output will be produced. With the
Low Voltage on, measure the voltage on both sides of F1 on the
Analog to Digital Converter and verify that it is approximately
+22 VDC. Measure the voltage on both sides of F2 and verity
that it is approximately -22 VDC. Measure the voltage on both
sides of F4 and verify that it is approxi8 VDC. If a fuse
has failed, replace the fuse and try again. If the fuse fails again,
troubleshoot the regulator circuit. Refer to SECTION K, Analog
to Digital Converter, and SECTION M, DC Regulator, for
additional information.
NOTE
It is sometimes possible for the regulator circuit to lock into a
fault condition if the output is accidentally shorted. If this oc-
curs, turn off the Low Voltage at CB1 and CB2 for approxi-
mately 1 minute to allow the power supply to discharge. Reap-
ply Low Voltage and note if the regulator is now reset.
6.24.2
Conversion Error Fault
The Analog to Digital Converter requires a sample of the RF
drive to develop the sample frequency for the A/D convertor IC.
If this sample is missing or there is a fault in the analog to digital
conversion process, the Conversion Error LED on the Color-
Stat™ panel will illuminate RED and circuitry on the Analog to
Digital Converter will generate a PA Turn-OFF command. The
PA Power Supply will remain energized but no RF output will
be produced. Refer to SECTION K, Analog to Digital Con-
verter, for additional information.
6.25
ColorStat™ panel Modulation
Encoder: Cable Interlock Fault
A Cable interlock will prevent a transmitter turn on command
from being generated. The step-start sequence will not begin
and the PA Power Supply will not energize. This prevents
possible damage to combiner toroids and RF amplifiers if cables
are removed or amplifiers are not installed in place on the
Combiner/Motherboards. The cable Interlock feature is accom-
plished through the individual Modulation Encoder and DC
Regulator cables. If the transmitter will not turn on and the Cable
Interlock LED is RED, check the following. Refer to SECTION
Section VI - Troubleshooting
Rev. R: 11-11-96
888-2297-002
6-13
WARNING: Disconnect primary power prior to servicing.
