Fan Control; Power Supplies; Temperature Monitoring - Tait TB8100 Service Manual

7.1.6

Fan Control

7.1.7

Power Supplies

7.1.8

Temperature Monitoring

TB8100 Service Manual
© Tait Electronics Limited September 2006
The fan is supplied from a +24V controlled supply on pin 13 of the IDC
connector (ground is on pin 14). The status of the fan supply voltage is
dependent on the operating temperature of the PA. The fan is turned on
when the PA operating temperature exceeds the user-defined thresholds set
using the Service Kit. The Service Kit also has an option to turn the fan on
only when the operating temperature exceeds the thresholds and the PA is
transmitting. The fan remains on until the operating temperature of the PA
falls to 5°C below the threshold temperature.
Power is supplied to the fan via the 16-way ribbon cable from the PA to the
subrack interconnect board. From there it is fed through the control panel
to the fan. If two PAs are fitted in a subrack, either PA will turn on the fan
when required.
Note
The PA fan must be in position and running to get an accurate
reading on the Air intake temperature gauge in the Service Kit.
You can use the fan test (Diagnose > Power Amplifier > Control
Tests) to make the fan run. Note also that the reading displayed
for a 100W PA may be slightly high, due to the location of the
temperature sensor board in the heatsink airflow.
The PA operates off a single +28VDC external power supply. The normal
range of operation is +26 to +30VDC. If the supply voltage falls to
between +24 and +26VDC or rises to between +30 and +32VDC, the PA
will reduce its output power to foldback levels. If the supply voltage falls
below +24VDC or rises above +32VDC, the PA will cease transmission
(shutdown).
The PA also has four internal power supplies to produce –3, +2.5, +5 and
+10VDC.
The PA monitors the temperatures of the 6W board, 60W board 1 and
60W board 2. The operating temperatures can be requested via an I
message.
If any board reaches the designated maximum temperature, the PA software
will report an alarm via the I
may be set using the Service Kit. In addition to activating alarms, the board
temperatures are also used to activate the PA fan, and power foldback. The
foldback thresholds are set in the factory and cannot be adjusted by the user.
A recovery hysteresis of 5°C is applied to all temperature thresholds.
2
C bus. The maximum temperature thresholds
Power Amplifier Circuit Description
2
C bus
119