Corrective Maintenance; Transistors And Integrated Circuits - Philips PM3208 Service Manual

7 CORRECTIVE MAINTENANCE
7.1 REPLACEMENTS
WARNING: The opening of covers or removal of parts, except those to which
access can be gained by hand, is likely to expose live parts, and also
accessible terminals may be live.
The instruments shall be disconnected from all voltage sources before
any adjustment, replacement or maintenance or repair during which
the instrument will be opened.
if afterwards any adjustment, maintenance or repair of the opened
instrument under voltage is inevitable, it shall be carried out only by a
qualified person who is aware of the hazard involved.
Bear in mind that capacitors inside the instrument may still be charged
even if the instrument has been separated from all voltage sources.
714A Standard parts
Electrical and mechanical replacement parts can be obtained through your local Philips
organisation or representative. However, many of the standard electronic components
can be obtained from other local suppliers.
Before purchasing or ordering replacement parts, check the parts list for value tolerance,
rating and description.
NOTE: . Physical size and shape of a component may affect instrument performance,
particularly at high frequencies. Always use direct-replacement components,
unless it is known that a substitute will not degrade instrument performance.
71.2 Special parts
in addition to the standard electronic components, some special components. are used.
-. Components manufactured or selected by Philips to meet specific performance
requirements.
7.1.3 Transistors and integrated circuits
Transistors and iC s (integrated circults) should not be replaced unless they are actually
defective. If removed from their sockets. during routine maintenance, return them to:heir
original sockets. Unnecessary replacement or exchanging of semiconductor devices may
affect the calibration of the instrument. When a transistor is replaced, check the
operation of the part of the instrument that may be affected.
WARNING: Handle silicone grease with care. Avoid getting silicone grease in ine
eyes. Wash hands thoroughly after use.
Any replacement component should be of the original type or a direct replacement.
7.1REPLACEMENTS