Motorola GM300 Series Manual de serviço básico - Página 18

Procurar online ou descarregar pdf Manual de serviço básico para Rádio Motorola GM300 Series. Motorola GM300 Series 46 páginas. Professional radio

3-2

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

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.

NOTE

Always use a fresh supply of alcohol and a clean container to prevent contamination by

dissolved material (from previous usage).

3.0

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.

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:

Store 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.

Ground 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.

Wear 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 RSX4015_.)

Do not wear nylon clothing while handling CMOS devices.

Do 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.

When straightening CMOS pins, provide ground straps for the apparatus used.

When soldering, use a grounded soldering iron.

If 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.

MAINTENANCE