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888-2406-002
WARNING: Disconnect primary power prior to servicing.
Overall System Theory
4.7.6.1.9 Forward Power Sample
The forward power sample from the directional coupler enters the Life Support
Board at J2. The sample is detected by CR8 and buffered by U1-14. The DC voltage
at TP8 is directly proportional to the forward power output of the transmitter. This is
sent to the Master Controller where it is used for monitoring, display, automatic
power control or APC and calibration.
4.7.6.1.9.1 CPLR_DISC_FAULT
This is an interlock fault which will mute the transmitter if the cable to the forward
directional coupler is disconnected. The fault line is pulled up through R1 to +5V. If
the coupler is connected, the line is pulled low and no fault occurs. When
disconnected, the line will pull high and the Master Controller will mute the
transmitter.
4.7.6.1.10 Reflected Power
The reflected power sample enters the board at J3. It is detected by CR10 and
buffered by U1-1. The voltage at TP7 is directly proportional to the amount of
reflected power coming back to the transmitter from the antenna or transmission
line. This DC sample voltage is sent to the Master Controller, via J1-A19, for
VSWR protection and monitoring when the Master Controller is operational. The
VSWR fault comparator output at U3-2 will only be able to effect transmitter
operation in Life Support Mode.
4.7.6.2 Life Support Mode
The following contains all pertinent circuit information for operating in the Life
Support Mode. This is when the Master Controller has failed and the Life Support
Board has taken over control of the transmitter.
4.7.6.2.1 Master Controller Failure
The Master Controller has what is referred to as a “Watchdog Timer”. As long as the
micro-controller on the Master Controller board is working and executing its
program normally, the Watchdog Timer will be sending out a pulse every 1.0msec.
These pulses are detected by 1/2 of U4 on the Life Support Board (U4-4), a re-
triggerable one-shot with a 2msec time-out, which will stay triggered (SET) as long
as the Watchdog Timer pulses continue. If the Watchdog Timer pulses are
interrupted (which means the Master Controller has failed), U4 will time-out and go
to the RESET mode. The Q output will go low and Q_NOT will go high. The low
signal from the Q output is inverted at U16-13, and pulls the
MASTER_NORMAL(BAR) signal high (this signal is normally low when the
Master Controller is working). The high Q_NOT signal at U4-7 is inverted at U16-
14 and U16-15. U16-14 pulls the MSTR_NORMAL 1 signal low while U16-15
pulls the MASTER_NORMAL signal low (these signals are normally high when
the Master Controller is working).
Содержание Platinum Z2 CD
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Страница 156: ...5 26 888 2406 002 WARNING Disconnect primary power prior to servicing Maintenance and Alignment ...
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