Chassis E9-service manual
GENERAL INSTRUCTIONS
X-RAY RADIATION
Picture tube is potential source of X-radiation of colour TV. Use exclusively original types of
replacement picture tubes, specified in technical documentation. Accelerating high voltage must not
exceed 30 kV. Supply voltage "B+" for horizontal output stage must be set according to the
specifications given in service manual.
SAFETY INSTRUCTIONS
Service interventions on colour TV can be performed by authorised and qualified personnel only,
considering the following instructions:
" During service interventions connect the TV set to mains voltage through separating (isolating)
transformer.
" During servicing procedures (replacement of individual components) disconnect the cord from mains
connector.
" After disconnection and before servicing wait about 30 sec. so that charged electrolytes and picture
tube are discharged.
" Provide for additional discharge of picture tube when replacing it and use protective means to
prevent injuries due to eventually broken glass.
" When changing modules or complete chassis, fix it with adequate elements (screws, latches, ...).
" Wires inside the TV set should not come in contact with sharp or hot areas.
" Integrated circuits and other semiconductors on chassis are sensitive to overvoltages and high
temperatures.
During service interventions they should be protected against too long heating with soldering iron (5
sec.), electrostatic discharges, short circuits between connectors etc. Therefore the following general
instructions should be followed:
" Use low impedance disconnecting transformer for connection of chassis to mains voltage.
" Use low voltage soldering irons with protective earthing.
" Chassis earthing should be equal to earthing of measuring and calibrating equipment and tools.
" When connecting instruments, first connect negative connector (mass, earth) and afterwards signal
connector.
" Voltages to be checked should be measured with suitable instruments. Do not use "short-circuit
methods" with pincets or screwdriver.
" Conductors under high voltage should not be placed near semiconductors on chassis.
" Installed IC?s, transistors and MOSFET?s are made in various semiconductor technologies (CMOS,
MOS, BIMOS or bipolar technology) and are more or less sensitive to exterior effects during
handling. All these elements should be handled in accordance with the requirements for
electrostatic protection. If these requirements are fulfilled, you prevent formation of undesired
electrostatic discharges which can destruct semiconductors or can activate destructive mechanisms,
which destroy circuit during operation.
Accumulated electrostatic charge is discharged through individual connectors of IC or transistor during
electrostatic discharges and current runs through semiconductor structure. Considering that thicknesses
of semiconductor substrate, used for IC, are very small, this current can cause damages to IC or destroy
it. For the protection of circuits the currents originating from discharges should be discharged under
control. This is obtained in the following ways:
" Staff handling the ICs should have earthed hands by means of a suitable wire and resistor.
" Working table should as well be earthed. Working surface should be made of conducting material
(conducting rubber), soldering irons and all required equipment should be earthed.
" Carrying and storing is permissible only in original packaging (antistatic tubes, conducting
sponges).
" If IC is mounted on a base, it should not be replaced under voltage.
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ACEC
