12/20/11
888-2595-001
4-13
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
ZX Series
The logic output of U13 is shifted via voltage divider network R78-R79 to
approxi2V when logic high and 0V when logic low. This line is diode-or
combined with +5V pulses coming from either the auto restart timer U14 or
optoisolator U30A controlled by the ON pushbutton and passed through buffer
transistor Q13 to increase its ability to drive low impedance loads. The result in the
ON_OFF_RESET signal which assumes the following values to command the PA & PS
modules in the transmitter chassis:
•
0V = Tx is off. Turn off all PS modules.
•
1V = Tx in on. Turn on all PS modules.
•
4V = Reset all faults.
NOTE:
The values have shifted slightly due to the voltage drop in the diode-or network
and the base-emitter junction of Q13.
The logic output of U13 can be overridden and forced to zero by transistor Q7 –
comparator U26C if the external interlock line is broken. This forces an emergency
transmitter shut down if the external interlock is not satisfied. A similar shutdown will
occur via transistor Q8 if the load temperature sensor circuit detects a combiner load
temperature in excess of 125 degrees centigrade.
Comparator U26D samples the logic output of U13 and provides a logic high output to
signal when the transmitter state is off. This status is available via the remote control
interface and also mutes the APC circuit by forcing the output of APC comparator
U25A to zero via CR10 (page 3).
4.12.1.1 Auto Restart
The purpose of the auto restart circuit is to send an ON command to restart PA modules
that may have shut off during a transient event such as an arc in the output transmission
line. The auto restart circuit sends +5V reset pulses from timer U14 at approximately
five second intervals whenever all of the following conditions are met:
•
Transmitter is latched ON (TX_OFF_STAT is false)
•
All PS modules are off. i.e. all PA modules have shut down (TX_ON_STAT
is false)
•
AC mains power is good (AC_FAULT is false)
•
The external interlock is satisfied (ILOCK_FAULT is false)
•
The restart circuit has not timed out (RESTART_FAULT is false)
Содержание ZX10
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Страница 80: ...3 12 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing Section 3 Operation ZX Series ...
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