Disassembling And Reassembling The Radio - General - Motorola HT750 - UHF/VHF/Low Band - Radio Service Manual

Maintenance
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
degree 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.
3.5 Disassembling and Reassembling the Radio — General
Since these radios may be disassembled and reassembled with the use of only four (board to casting)
screws, it is important to pay particular attention to the snaps and tabs, and how parts align with each
other.
The following tools are required for disassembling the radio:
3/16" flat blade screwdriver
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Penknife-size screwdriver
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TORX™ T6 screwdriver
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If a unit requires more complete testing or service than is customarily performed at the basic level,
send this unit to a Motorola Authorized Service Center. (See Chapter, section 1.2.4 Technical Support
on page 1-3 for a list of authorized service centers.)
The following disassembly procedures should be performed only if necessary:
section 3.6.2 Chassis Assembly/Disassembly on page 3-6
section 3.6.3 Keypad, Display, and Keypad/PassPort/Option Board Disassembly on page 3-6
section 3.6.4 Speaker, Microphone, and Universal Connector Flex Disassembly on page 3-8
section 3.6.5 PTT Disassembly on page 3-9
section 3.6.6 Control Top Disassembly on page 3-9
section 3.7.7 DTMF Retrofit Kit Procedure (Optional Upgrade Procedure) on page 3-12
section 3.7.8 Option Board Installation on page 3-13
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