Safe Handling Of Cmos Devices; Repair Procedures And Techniques - Motorola HT-1000 Service Manual

Safe Handling of
CMOS Devices
Repair Procedures
and Techniques
General
Parts Replacement and
Substitution
Rigid Circuit Boards
42
Alcohol is a high-wetting liquid and can carry contamination into
unwanted places if an excessive quantity is used. Make sure that
controls or tunable components are not soaked with the liquid. Do not
use high-pressure air to hasten the drying process, since this could
cause the liquid to puddle and collect in unwanted places.
Upon completion 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).
Complementary metal-oxide semiconductor (CMOS) devices are used
in this family of radios. While the benefits of CMOS are many, their
characteristics make them susceptible to damage by electrostatic or
high voltage charges. Damage can be latent, resulting in failures
occurring weeks or months later. Therefore, you must take special
precautions 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 CMOS CAUTION paragraph in the Disassembly and
Reassembly section of the manual.
Refer to the Disassembly and Reassembly section of the manual for
pertinent information prior to replacing and substituting parts.
Special care should be taken to be as certain as possible that a
suspected component is actually the one at fault. This special care will
eliminate unnecessary unsoldering and removal of parts, which could
damage or weaken other components or the printed circuit board
itself.
When damaged parts are replaced, identical parts should be used. If
the identical replacement component is not locally available, check
the parts list for the proper Motorola part number and order the
component from the nearest Motorola Communications Parts office
listed in the "Replacement Parts Ordering" section of this manual.
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, care should be exercised to avoid pulling the plated
circuit out of the hole.
When soldering near the module socket pins, use care to avoid
accidentally getting solder in the socket. Also, be careful not to form
solder bridges between the module socket pins. Closely examine your