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 of the radio are clean, and that all external controls and switches are 
functional. It is not recommended to inspect the interior electronic circuitry.
3.2.2 Cleaning Procedures
The following procedures describe the recommended cleaning agents and the methods to be used 
when cleaning the external and internal surfaces of the radio. External surfaces include the front 
cover, housing assembly, and battery case. These surfaces should be cleaned whenever a periodic 
visual inspection reveals the presence of smudges, grease, and/or grime.
The only recommended agent for cleaning the external radio surfaces is a 0.5% solution of a mild 
dishwashing detergent in water. The only factory recommended liquid for cleaning the printed circuit 
boards and their components is isopropyl alcohol (70% by volume).
Cleaning External Plastic Surface
Apply the 0.5% detergent-water solution sparingly with a stiff, non-metallic, short-bristled brush to 
work all loose dirt away from the radio. Use a soft, absorbent, lintless cloth or tissue to remove the 
solution and dry the radio. Make sure that no water remains entrapped near the connectors, cracks, 
or crevices
Cleaning Internal Circuit Boards and Components
Isopropyl alcohol (70%) may be applied with a stiff, non-metallic, short-bristled brush to dislodge 
embedded or caked materials located in hard-to-reach areas. The brush stroke should direct the NOTE: Internal surfaces should be cleaned only when the radio is disassembled for service 
or repair.
CAUTION: Certain chemicals and their vapors can have harmful effects on certain 
plastics. Avoid using aerosol sprays, tuner cleaners, and other chemicals.!
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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
Complementary metal-oxide semiconductor (CMOS) devices are used in this family of radios, and are 
susceptible to damage by electrostatic or high voltage charges. Damage can be latent, resulting in 
failures occurring weeks or months later. Therefore, special precautions must be taken to prevent 
device damage during disassembly, troubleshooting, and repair. 
Handling precautions are mandatory for CMOS circuits and are especially important in low humidity 
conditions. DO NOT attempt to disassemble the radio without first referring to the following CAUTION 
statement. 
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 the “Piece Parts” section of this manual 
(See page 1-2).NOTE: Always use a fresh supply of alcohol and a clean container to prevent contamination 
by dissolved material (from previous usage).
CAUTION: This radio contains static-sensitive devices. Do not open the radio unless 
you are properly grounded. Take the following precautions when working on this 
unit:
lStore and transport all CMOS devices in conductive material so that all exposed 
leads are shorted together. Do not insert CMOS devices into conventional plastic 
“snow” trays used for storage and transportation of other semiconductor devices.
lGround the working surface of the service bench to protect the CMOS device. We 
recommend using the Motorola Static Protection Assembly (part number 
0180386A82), which includes a wrist strap, two ground cords, a table mat, and a 
floor mat.
lWear a conductive wrist strap in series with a 100k resistor to ground. 
(Replacement wrist straps that connect to the bench top covering are Motorola 
part number RSX-4015.)
lDo not wear nylon clothing while handling CMOS devices.
lDo not insert or remove CMOS devices with power applied. Check all power 
supplies used for testing CMOS devices to be certain that there are no voltage 
transients present.
lWhen straightening CMOS pins, provide ground straps for the apparatus used.
lWhen soldering, use a grounded soldering iron.
lIf at all possible, handle CMOS devices by the package and not by the leads. Prior 
to touching the unit, touch an electrical ground to remove any static charge that 
you may have accumulated. The package and substrate may be electrically 
common. If so, the reaction of a discharge to the case would cause the same 
damage as touching the leads.
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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. 
lBe careful not to form solder bridges between the connector pins. 
lExamine your work closely for shorts due to solder bridges.
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.
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:
l3/16” flat blade screwdriver
lPenknife-size screwdriver
lTORX™ T6 screwdriver
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 3-13NOTE: Do not attempt to puddle-out components. Prolonged application of heat may 
damage the flexible circuit. 
						

							3-4Maintenance
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 supposed to fit very tightly on their 
shafts.
Battery
Battery
Release
Buttons
Knobs 
						

							Maintenance3-5
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 forces the thin inner plastic wall toward the base of the radio, releasing the 
two chassis base tabs.
Figure 3-3:  Chassis Removal 
6. Lay the chassis down. Rotate the front cover backward and slightly away from the chassis.
5. Lift the latches on the main circuit board to release the flexes from their connectors.
Figure 3-4:  Unlatch Flex Connectors
CAUTION: Marring the front cover O-ring sealing area will prevent the radio from 
sealing properly.
NOTE: Flexible ribbon circuits (flexes) connecting the front cover assembly and the 
chassis prevent you from completely separating the two units. Display radios and 
radios with option boards have two flexes. 
Radio 
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Flex ConnectorLatches 
						

							3-6Maintenance
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, slide off the ground contact from the top corner boss of the radio 
chassis.
3.6.3 Keypad, Display, and Keypad/PassPort/Option Board Disassembly
1. If the disassembly of the keypad or the keypad printed circuit board, is required, lift the 
microphone flex circuit up, and carefully remove the microphone and its boot from the front cover 
pocket. (See Figure 3-6 on page 3-7).
2. Lay this flex circuit to one side.NOTE: At this point, if necessary, the DTMF Retrofit Kit Procedure can be performed. 
(See section 3.7.7 DTMF Retrofit Kit Procedure (Optional Upgrade Procedure) on page 
3-12).
CAUTION:  Refer to the CMOS CAUTION in paragraph on page 3-2 before removing 
the main board. Be sure to use electrostatic discharge (ESD) protection when 
handling circuit boards.
Main 
Board
Screws (4)
Radio
Chassis
O-Ring
Retaining
Features
Compliant
Ground
Contact
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							Maintenance3-7
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 the front cover, then lift and pivot the two hooks out of the front 
cover.
5. If disassembly involves the removal of the display module, disconnect the display flex from the 
keypad option board connector by lifting the latch on the connector. (This is similar to the process 
for releasing the flexes.) (see page 3-5.)
6. The display module is attached to the front cover with a double-sided adhesive pad. Carefully pull 
up on the display module, using a small screwdriver, if necessary, and remove it from the front 
cover. Use a new piece of double-sided adhesive to re-mount the display to the cover.
7. The keypad/PassPort/option board can be removed without the use of tools.
CAUTION Take care not to damage the display. Do not cut, bend, or pinch the heat 
seal. Display modules contain CMOS devices. Be sure to use ESD protection.
Flat Blade
ScrewdriverSpeaker-Microphone
Flex Circuit Tail
Keypad Retainer
Arm Tabs (4)
Retainer
Top HooksRetainer
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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 the retainer by slightly pushing it toward the top of the radio 
until you slide it past the front cover slot.
3. Pull the rubber microphone boot from its seated position. Unless you are replacing the 
microphone, leave it in the boot.
4. Peel-off the universal connector flex circuit escutcheon (label).
5. Pry the flex circuit (adhesive held) backer board away from the front cover, and remove the 
universal connector tail of the speaker-microphone assembly through its opening in the front 
cover. NOTE: At this point, the Option Board Installation Procedure should be performed, if 
necessary. (See page 3-13)
NOTE: The dustcover must be removed to remove the speaker-microphone assembly flex 
circuit. The speaker is held in place with a two-legged retainer bracket. The bracket 
legs are secured by the front cover slots. Be careful not to damage the speaker when 
removing the retainer bracket.
NOTE: The speaker-microphone assembly flex circuit goes through the front cover wall to 
the outside wall. To replace this assembly, you must peel-off the universal connector 
escutcheon label. The existing escutcheon cannot be reassembled; a new part must 
be used. (See item number 10 on the exploded view drawing on page 3-15).
Retainer
Display
Module
Keypad
Option
Board
Keypad
Radio
Body 
						

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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 assembly can be disassembled using a small screwdriver 
as follows:
Figure 3-7:  PTT Removal 
1. Pry back the T-tab found inside the front cover (in between the four buttons on the PTT 
assembly). 
2. Remove the PTT bezel by slightly bowing it until the top and bottom tabs are released from the 
slots in the front cover. 
3. The PTT seal can be easily lifted from the bezel without the use of tools. 
3.6.6 Control Top Disassembly
1. To remove the control top assembly, place a screwdriver next to the antenna boss, then pry it 
against the control top escutcheon. This lifts the control top escutcheon away from its 
double-sided adhesive. Grab the double-sided adhesive near the volume potentiometer, then lift it 
away.
2. Remove the integrated control top seal, emergency button, and transmit light pipe.
Speaker
Universal
Connector
Ta i l
Microphone
Boot
Microphone
Speaker Microphone
Flex Circuit Assembly
Speaker Orientation
Tab (12:00 Position)
Ta b
PTT
Bezel
T-Shaped
Retainer Tab
Ta b
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 slot. 
3. Press the PTT assembly against the front cover opening.
3.7.3 Speaker, Microphone, and Universal Connector Flex Reassembly
1. Feed the universal connector tail of the speaker-microphone flex assembly through the opening in 
the side wall of the front cover.
2. Peel-off the adhesive liner on the back of the universal connector tail of the flex circuit. Attach the 
flex tail to the front cover using the guide pins for correct alignment.
3. Replace the universal connector escutcheon. Make sure that all the connector openings align 
with the gold pads on the flex circuit.
4. Align the notch in the speaker at the twelve o’clock position with the tab on the front cover as 
shown in Figure 3-8.
5. Place the speaker retainer bracket into the hole on the top of the front cover, and bend the 
retainer down to fit underneath the boss below the speaker.
6. If display, keypad, or keypad option board are not involved, reinsert the microphone and boot into 
the pocket in the front cover
3.7.4 Keypad, Display, and Keypad/PassPort/Option Board Reassembly
1. If you are replacing the display, use a new double-sided adhesive display pad (item number 17 on 
the exploded view diagram in paragraph 3-8). 
2. Replace the keypad, and the keypad/option board. Make sure the display module flex tail is 
connected to the connector on the keypad/option board.
3. Insert the “top hooks” of the keypad retainer into the slots below the speaker (above the display) 
in the front cover. Snap all four of the retainer arm tabs in place in the front cover.
4. Reinsert the microphone and boot into the pocket in the front cover.
5. Lay the speaker-microphone flex on top of keypad/PassPort/option board retainer.NOTE: Look inside the front cover to make sure the T-tab is fully engaged with the front 
cover. If necessary, press the T-tab toward the top of the radio until it becomes fully 
engaged. 
NOTE: Pull the speaker-microphone flex circuit out of the way during reassembly.