Motorola MTP850, Service Manual

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6 - 2 MTP850 TETRA Handportable Terminal / Basic Service Manual MAINTENANCE
Cleaning External Plastic Surfaces
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 (100%) 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 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.
Safe Handling of CMOS Devices
Complementary metal-oxide semiconductor (CMOS) devices are used in the
radio. While the attributes of CMOS devices are many, their characteristics make
them susceptible to damage by electrostatic or high voltage charges. Damage
can be latent, resulting in failure occurring weeks or months later. Therefore,
special precautions must be taken to prevent device damage during disassembly,
troubleshooting, and repair. The following handling precautions are mandatory
for CMOS circuits, and are especially important in low humidity conditions.
• All CMOS devices must be stored or transported in conductive material so that
all exposed leads are shorted together. CMOS devices must not be inserted
into conventional plastic “snow” or plastic trays of the type that are used for
storage or transportation of other semiconductor devices.
• All CMOS devices must be placed on a grounded bench surface and the
technician must also be grounded before handling the devices. This is done
most effectively by having the technician wear a conductive wrist strap in
series with a 100k
Ω
resistor to ground.
• Do not wear nylon clothing while handling CMOS circuits.
• Do not insert or remove CMOS devices with power applied. Check all power
supplies to be used for testing CMOS devices and be certain there are no
voltage transients present.
• When straightening CMOS device leads, provide ground straps for the
apparatus used.
• When soldering, use a grounded soldering iron.
• All power must be turned off in a system before printed circuit boards
containing CMOS devices are inserted, removed, or soldered.
NOTE: Always use a fresh supply of alcohol and a clean container to prevent
contamination by dissolved material (from previous usage).