Repair Procedures And Techniques - General - Motorola EX500 Basic Service Manual

Repair Procedures and Techniques — General
3.4 Repair Procedures and Techniques — General
Parts Replacement and Substitution
When damaged parts are replaced, identical parts should be used. If the identical replacement part is
not locally available, check the parts list for the proper Motorola part number and order the part from
the nearest Motorola Communications parts center listed in section 1.2.3 on page 1-2 of this manual.
Rigid Circuit Boards
This family of radios uses bonded, multi-layer, printed circuit boards. Since the inner layers are not
accessible, some special considerations are required when soldering and unsoldering components.
The printed-through holes may interconnect multiple layers of the printed circuit. Therefore, exercise
care to avoid pulling the plated circuit out of the hole.
When soldering near the 20-pin and 40-pin connectors:
Avoid accidentally getting solder in the connector.
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Be careful not to form solder bridges between the connector pins.
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Examine your work closely for shorts due to solder bridges.
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Flexible Circuits
The flexible circuits are made from a different material than the rigid boards, and require different
soldering techniques. Excessive prolonged heat on a flexible circuit can damage the material.
Therefore, avoid excessive heat and excessive bending.
For parts replacement, use the ST-1087 Temperature-Controlled Solder Station with a 600-700°F tip,
and use small diameter solder such as ST-633. The smaller size solder will melt faster and require
less heat to be applied to the circuit.
To replace a component on a flexible circuit:
1. Grasp with seizers (hemostats) the edge of the flexible circuit near the part to be removed.
2. Pull gently.
3. Apply the tip of the soldering iron to the component connections while pulling with the seizers.
NOTE Do not attempt to puddle-out components. Prolonged application of heat may damage the
flexible circuit.
Chip Components
Use either the RLN-4062 Hot-Air Repair Station or the Motorola 0180381B45 Repair Station for chip
component replacement. When using the 0180381B45 Repair Station, select the TJ-65 mini-
thermojet hand piece. On either unit, adjust the temperature control to 700°F. (370°C), and adjust the
airflow to a minimum setting. Airflow can vary due to component density.
To remove a chip component, select a hot-air hand piece and position the nozzle of the hand
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piece approximately 1/8" above the component to be removed. Begin applying the hot air. Once
the solder reflows, remove the component using a pair of tweezers. Using solder wick and a
soldering iron or a power desoldering station, remove the excess solder from the pads.
To replace a chip component using a soldering iron, select the appropriate micro-tipped
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soldering iron and apply fresh solder to one of the solder pads. Using a pair of tweezers, position
the new chip component in place while heating the fresh solder. Once solder wicks onto the new
component, remove the heat from the solder. Heat the remaining pad with the soldering iron and
apply solder until it wicks to the component. If necessary, touch up the first side. All solder joints
should be smooth and shiny.
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