Motorola Two Way Portable Radio Ht750 Ht1250 Mtx850 Mtx1250 Mtx8250 Mtx9250 Basic 68p80906z54 D Manual

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Chapter 3
Maintenance
3.1 Introduction
This chapter provides details about the following:
lPreventive maintenance (inspection and cleaning) 
lSafe handling of CMOS and LDMOS devices
lDisassembly and reassembly of the radio
lInstallation of Optional Retrofit Kit
lInstallation of Option Boards
3.2 Preventive Maintenance
The radios do not require a scheduled preventive maintenance program; however, periodic visual 
inspection and cleaning is recommended.
3.2.1 Inspection
Check that the external surfaces...

3-2Maintenance
dislodged material out and away from the inside of the radio. Make sure that controls or tunable 
components are not soaked with alcohol. Do not use high-pressure air to hasten the drying process 
since this could cause the liquid to collect in unwanted places. After completing of the cleaning 
process, use a soft, absorbent, lintless cloth to dry the area. Do not brush or apply any isopropyl 
alcohol to the frame, front cover, or back cover.
3.3 Safe Handling of CMOS and LDMOS Devices...

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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: 
lAvoid accidentally getting solder in the connector....

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3.6 Detailed Radio Disassembly
3.6.1 Front Cover from Chassis Disassembly
1. Turn off the radio.
2. Remove the battery:
a. Pull down on the two battery-release buttons.
b. With the buttons pulled down, the top of the battery will fall from the radio.
c. Remove the battery completely from the radio.
Figure 3-1: Battery Removal
3. Remove the antenna.
3. Pull the volume and channel selector knobs off their shafts.
Figure 3-2:  Knob Removal  NOTE: Both knobs slide on and off. However, they are...

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4. Separate the chassis from the internal electronics front cover assembly as follows:
a. Insert a small, 3/16” flat-blade screwdriver, or similar instrument, in between the thin 
remaining wall and the chassis at the bottom of the radio. Do not mar the O-ring sealing area 
on the housing.
b. Slowly pry the bottom of the chassis from the cover by pushing the 3/16” flat-blade 
screwdriver down, and rotating the handle of the tool over and behind the base of the radio. 
This prying action...

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3.6.2 Chassis Assembly/Disassembly
1. If disassembly of the chassis or the main board is required, then use a TORX™ screwdriver with 
a T6 head to remove the four screws holding the main board to the chassis.
Figure 3-5: Remove Main Board from Chassis
2. Lift the main board from the chassis (refer to Figure 3-5).
3. Remove the small O-ring retainers from their slots in the chassis. Note the alignment of the 
retainers for reassembly.
4. Remove the O-ring.
5. If required in disassembly,...

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3. To remove the keypad retainer shield:
a. Insert the tip of a “penknife size,” flat blade screwdriver in the opening at the end of the 
keypad retainer arm tab. 
b. Pry the tab away from the side of the front cover until it moves past the ledges on the side 
wall. Repeat this procedure for the four remaining retainer arm tabs.
Figure 3-6: Remove Retainer
4. Note that the two “top hooks” are still held underneath the front cover—right below the speaker. 
Lift the keypad retainer out of...

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Figure 3-5:  Removing the Keypad Retainer and Other Boards from the Radio
3.6.4 Speaker, Microphone, and Universal Connector Flex Disassembly
1. If disassembly of the speaker-microphone assembly is necessary, remove the dustcover by 
turning the screw at the bottom of the dustcover counterclockwise with your fingers. Lift the 
dustcover out of its pocket.
2. Using a screwdriver, push down on the portion of the speaker retainer bracket pointing toward the 
bottom of the radio. Then, remove...

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6. After the universal connector tail of the speaker-microphone assembly is removed, the assembly 
can be completely removed. If it is necessary to replace the speaker or microphone, or both, do it 
while the flex circuit is removed from the front cover. When reassembling the microphone in its 
boot, make sure the microphone port faces the round hole in the bottom of the boot.
Figure 3-6:  Removal Speaker-Microphone Assembly
3.6.5 PTT Disassembly
If required, the PTT bezel and the PTT seal...

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3.7 Detailed Radio Reassembly
3.7.1 Control Top Reassembly
1. Replace transmit light pipe and control top seal. 
2. Peel off the liners from a new control top escutcheon and place it in the recess in the front cover. 
Press the control top escutcheon firmly against the adhesive.
3.7.2 PTT Reassembly
1. Put the PTT seal in the PTT bezel.
2. Place the bezel top tab in the top slot inside the front cover PTT opening. Slightly bow the bezel 
so that the bottom tab can fall inside the bottom...