8525B/8528 Technical Service Manual Maintenance 6-3
Publication No: 15-02036 Issue 6
• Integrated circuit replacement—In some cases it is possible to desolder
and remove components from the board without damage to the
component or the board. However, integrated circuits with a large
number of connections, mounted on double-sided circuit boards with
plated-through holes are almost impossible to remove intact, and the
operation is likely to damage the circuit boards. To replace these
components their leads must be cut individually until the body of the
component can be removed from the board. Individual leads must then
be unsoldered and removed. Excess solder must be removed before
inserting the replacement component.
6.1.3 Transmitter Precautions
When making measurements of the low level stages of the exciter it is
advisable to remove the drive to the PA stages by disconnecting P2 on the
PA and filter PCB. The supply voltage is applied to the PA at all times when
the transceiver is switched on. Due care should be exercised when
connecting probes.
6.1.4 Probe Precautions
The following should be observed when connecting CRO probes to the
transceiver:
• When connecting probes to the PA assembly, the earth clip lead should
be wound around the body of the probe so that the earth clip just
reaches the probe tip. This reduces stray pick-up.
• The earth clip should be connected to the ground plane immediately
adjacent to the point of measurement to which the probe tip is
connected.
• It is not advisable to connect two probes at the same time, particularly
when one is earthed to the PA ground plane and the other is earthed to
the chassis, as this may cause earth loop problems.
• Probes should be connected after power has been applied to the
transceiver and the test equipment. The earth connection should be
made first and disconnected last.
6.1.5 Surface Mounted Components
Surface mounted components are used on some printed circuit boards. For
removal and replacement of these components it is essential to use tools
specifically designed for the purpose. Repairs to these boards should not be
attempted unless the appropriate tools are available.
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