Microprocessor Control Circuitry; Diagnostics And Alarms - Tait TB8100 Service Manual

7.1

Microprocessor Control Circuitry

7.1.1

Diagnostics and Alarms

TB8100 Service Manual
© Tait Electronics Limited September 2006
Refer to Figure 7.2 on page
The PA has a microprocessor which performs the following functions:
monitors the operating conditions of the PA
controls the RF power level
reports faults (by generating alarms)
takes preventative action to protect the PA under fault conditions.
The alarms and diagnostics are accessed through I
reciter, control panel and Service Kit.
There are no manual adjustments in the PA because all the calibration
voltages and currents required to control and protect the PA are monitored
by the microprocessor. The software also automatically detects the PA
configuration and controls the PA accordingly.
The diagnostic functions and alarms monitored by the PA include:
the temperature of the 6W board
the temperatures of 60W board 1 (50W and 100W PAs) and 60W
board 2 (100W PA)
the ambient temperature of the intake air (ambient temperature is
defined as the temperature of the air from the cooling fan; the PA fan
must be in position and running to get an accurate reading in the Service
Kit)
forward and reverse power
load VSWR
the transmit current of the 6W driver transistor
the transmit current of the final transistors on 60W board 1 (50W and
100W PAs) and 60W board 2 (100W PA)
the current imbalance between the final transistors on 60W boards 1 and
2 (100W PA)
the supply voltage
the summary alarm.
Most alarms have two thresholds. The first threshold activates the alarm and
is usually set by the user via the Service Kit. The second threshold defines
the limit of operation of the PA and the software will either foldback the RF
transmit power or suspend transmission until the fault condition is
recovered. The values for the second threshold are set in the factory and
cannot be changed. In all instances there is a small amount of hysteresis
between the value at which the alarm, foldback or shutdown activates and
the value at which the alarm or shutdown is cleared.
117.
2
Power Amplifier Circuit Description
C bus messages via the
115