Maintenance 5-8 X-2 Technical Service Manual
Publication No: 15-02047
5. Check, whilst changing channels, the Enable, Data and Clock pulses
are present at input of synthesizer integrated circuits IC5
[F5]
at pins 12,
10 and 11 and IC11
[G7]
at pins 13, 12 and 11.
6. If only VCO2 is unlocked and the previous checks appear correct,
incorrect alignment may be the cause of failure. Re-set VCO2 as
detailed in the VCO2 Adjust Section 7.6.3.
5.3.6 PA Failure
To optimise the amplifier performance, the PA output transistors are
matched in pairs by a coloured dot or letter code. Measurements in this area
depend upon the matched pair of transistors fitted and the frequency of
transmission.
Table 5.1 provides a guide to the peak to peak voltages expected at the
specified points in the PA circuit. They are given for full power output when
driven with a two-tone input. For these tests the supply voltage should be
13.6 V and the output terminated into 50 Ω.
Frequency Battery V10
(Vpp)
V11
(Vpp)
V13/V14
(Vpp)
V18/V19
(Vpp)
(MHz) (Amps) E C E C B C B
2.5 9.5 0.20 0.40 0.20 1.10 0.20 20 2.2
3.5 9.5 0.20 0.45 0.25 1.10 0.20 20 2.3
5.5 9.5 0.25 0.45 0.25 1.10 0.20 25 2.7
8.5 10.0 0.35 0.60 0.40 1.20 0.27 28 3.2
15.5 9 0.55 1.30 0.60 1.00 0.70 35 4.0
17.9 10.0 0.60 1.50 0.60 1.10 0.80 20 4.5
Table 5.1: Peak to Peak Voltages
5.4 Dismantling and Assembling
5.4.1. General
It may be necessary to remove printed circuit boards from the transceiver in
order to carry out certain repairs. The following paragraphs give instructions
on the removal and installation of the boards. While carrying out these
procedures the following general points should be observed:
Screwdriver
Screws with Pozidrive heads are used in almost all locations. Ensure that the
appropriate screwdriver of the correct size is used.
To Next Page
Loading...
Need help?
General
