Tait TB7100, Service Manual

Page: 226 / 370

228 Transmitter Fault Finding (25W) TB7100 Service Manual
© Tait Electronics Limited October 2005
13.2 Transmitter RF Power
Introduction
If there is no fault with the power supplies, check the transmitter RF power
and correct any fault. The procedure is covered in the following eight tasks:
■
Task 4 : check forward and reverse powers
■
Task 5 : check RF output power
■
Task 6 : power unchanged regardless of setting
■
Task 7 : check for inhibiting of transmitter
■
Task 8 : check temperature sensor
■
Task 9 : power and current are skewed
■
Task 10 : repair output matching circuitry
■
Task 11 : power and current are low
The measurement points for diagnosing faults concerning the transmitter
RF power are summarized in
Figure 13.5 . Data required for the first task
(checking the forward and reverse powers) are supplied in Table 13.3 .
Table 13.3 Voltages in millivolts corresponding to nominal forward and reverse powers
Frequency band Forward power (318 command) Reverse power (319 command)
B1 1100 to 2000 < 500
H5 2500 to 3500 < 1000
H6 2800 to 3900 < 1000