Circuit Boards - Codan X-2 Service Manual

Maintenance 5-2
5.2.2

Circuit Boards

When servicing printed circuit boards the following should be observed:
Excessive heat
Excessive heat may lift the track from circuit boards, causing serious
damage. Avoid the use of high powered soldering irons. A 60W maximum
iron, preferably temperature controlled at approximately 370°C, is sufficient
for most tasks. A slightly higher temperature (425°C) iron may be required
for heavier components such as PA transistors. Apply the iron only long
enough to unsolder an existing joint or to solder a new one.
Unsoldering
When unsoldering use a solder-sucker or Solderwick to remove solder.
Do not use sharp metal tools such as screwdrivers or twist drills as these
will damage the printed circuit track.
Component substitution
Avoid unnecessary component substitution as this may damage the
component, the circuit track or adjacent components.
Component replacement
When a component is diagnosed as defective, or the fault cannot be
diagnosed in any other way than by substitution, observe the following when
installing replacement:
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•
Never force the leads through the holes as this will damage the circuit track,
particularly where plated through holes are used.
Axial leads - Components with axial leads, such as resistors and tubular
capacitors, can often be replaced without unsoldering the joints on the
boards. The defective component can be removed by clipping its leads
close to the component leaving the leads soldered to the board. These
leads should be straightened so that the leads of the replacement can be
wrapped around them and soldered. After soldering, the excess lead
should be clipped off.
Remove solder - When a component has been unsoldered from the
board ensure the holes are clear of solder before inserting the leads of
the replacement.
X-2 Technical Service Manual
ICAUTION
ICAUTION
Publication No: 15-02047