Harris DX 25U, Техническое руководство

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remote “Reset” control input must be received to reset fault
INDICATIONS.
Q.4.2
Type 2 Faults
An RF Overdrive, RF Underdrive or a Supply Current Overload
generates a “Type 2 Fault” signal, a logic HIGH pulse approxi-
mately 1 second long. This pulse goes to the turn-on/turn-off
logic on the Controller to cycle the transmitter OFF and then
back ON. If the same fault occurs again when the transmitter is
cycled back ON, a “Fault-H” output goes to U19-10. The Type
2 fault then becomes a Type 1 fault and turns the transmitter
OFF.
An “RF Drive Estimate,” an analog voltage, is also derived from
the Underdrive Fault Sense circuit. This voltage provides an
uncalibrated RELATIVE RF DRIVE indication on the front
panel multimeter and also provides an uncalibrated remote “RF
Drive Estimate” reading.
A “Supply Current” sample, an analog voltage, is derived from
the Supply Current Overload sense circuit for remote current
metering.
Inhibit inputs from the Controller operate during transmitter
turn-on. These inputs disable fault sensing until RF drive has
time to stabilize and prevent false indications when AC power
is initially applied or is re-applied to the transmitter.
The “Reset A” and “Reset B” function is the same as for Type
1 Faults.
Q.4.3
Type 3 Faults
Type 3 Faults are VSWR faults or Temperature Induced
LOWER faults. Single VSWR “hits” simply turn the PA OFF
for 14 to 19 milliseconds, by a “VSWR-H” logic pulse to “PA
Off” OR gate U40. Long-term reflected power causes repeated
VSWR “hits” which lower transmitter power until the reflected
power is below the VSWR detector threshold. A “VSWR/Temp
Induced Lower” logic signal to the Controller operates the
LOWER command.
Inputs to “Type 3 Fault” VSWR logic on the LED Board are
logic LOW pulses from the Output Monitor, and a logic HIGH
input from the Driver Encoder/Temp Sense Board.
In addition to the “VSWR-H” logic pulse to PA Off Gate U40,
the VSWR Logic on the LED Board also generates an RF Drive
Switch-over logic signal, a VSWR/Temp Induced Lower Com-
mand, a remote “Type 3 Fault” status indication logic output,
and a “VSWR-H” logic signal to the VSWR Self-Test circuits.
A “Controller Supply Fault-L” input disables fault circuits to
prevent false indications when AC power is initially applied or
is re-applied.
The “Reset A” and “Reset B” function is the same as for Type
1 Faults.
Additional descriptions for circuits using the output from the
VSWR Fault Logic can be found as follows:
a. RF Drive Switch-over signal: Refer to SECTION A, Os-
cillator.
b. VSWR Induced Lower: Refer to SECTION P, Controller.
The VSWR Self-Test circuit checks the VSWR Fault logic by
simulating a VSWR signal from the Output Monitor phase
detector output. The VSWR Fault logic circuit is checked each
time AC power is initially applied or re-applied. There is also a
Manual SELF TEST button on the ColorStat™ panel to check
the operation of the circuit at any time.
NOTE
Depressing this button will cause a PA OFF command, and out-
put power will momentarily decrease.
Q.4.4
Type 4 Faults
Type 4 faults include all supply faults on the Analog Input Board
and Analog to Digital Converter. A supply fault on either board
affects the digital data to the PA modules. A Type 4 Fault
generates a “PA Off” output to the modulation encoder and turns
all PA modules OFF.
Q.4.5
Type 5 Faults
Type 5 Faults are Conversion Error faults generated by circuits
on the Analog to Digital Converter and then sent to a status
indicator circuit on the LED Board. For a description of Con-
version Error fault circuits, refer to SECTION K, Analog to
Digital Converter.
Q.4.6
Type 6 Faults
Type 6 Faults are Blown Fuse faults from an open B+ fuse on a
PA Module. A PA Module failure results in missing “Steps” that
make up the modulated RF signal. Blown Fuse faults generate
a “Fault” status indication to alert the operator of a Fault
condition, but do not result in any change in the operation of the
transmitter.
Q.4.7
RF Sense Circuits
RF Sense circuits on the LED Board operate “Oscillator,”
“Buffer,” and “Predriver” indicators on the ColorStat™ panel.
If RF output is present at each stage, all three status indicators
are GREEN. If a stage fails, the status indicator for that stage
will be RED.
Q.4.8
Reset Circuit
The RESET circuit resets Type 1, Type 2 or Type 3 Fault LED
INDICATIONS on the ColorStat™ panel. Fault DETECTION
circuits act whenever a fault is present, whether the LED indi-
cation has been “reset” or not. As soon as a fault is cleared, the
transmitter can be turned back ON, even if the indication has not
been “reset.”
As long as a Type 1 Fault is present, the transmitter will remain
OFF and cannot be turned back ON (except for “Supply Fault”
and “Overvoltage” faults which will turn the transmitter OFF
during or immediately after the step-start sequence if still pre-
sent).
For Type 2 faults, the transmitter can be turned ON again, but if
the cause of the fault remains (Supply Overload, Overdrive or
Underdrive), the Type 2 fault circuits will operate again.
DX-25U
Q-4 888-2297-002 Rev. R: 11-11-96
WARNING: Disconnect primary power prior to servicing.