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SAFETY AND ISOLATION
SAFETY AND ISOLATION
Under no circumstances should any form of repair or
maintenance be attempted by any person other than a
competent technician or engineer. Most of the circuitry on
the chassis is isolated from the AC supply by T801, C831,
R821, IC802 and 6mm air gaps. To maintain this safety
factor ensure that, after repair, any gaps or leakage paths
are not reduced by protruding wires etc., following
component replacement
NOTE: although the output supply paths from the power
supply section are isolated from the incoming AC supply, the
bridge rectifier and the control and regulation circuits are not
isolated. Therefore, when servicing the power supply section
of the chassis, the AC supply should be connected via an
isolating transformer of at least 200 watts rating.
The power supply section remains charged with respect to
chassis for 30–60 seconds after switching off. Care should
be taken to avoid touching the power supply area of the
chassis during this time.
Components marked ! in the parts list are safety approved
types and should be replaced only with components supplied
or approved by our Service Department. It is also
recommended that components not marked with the safety
symbol should be replaced with parts of the type originally
fitted. This applies particularly to those resistors which are
'stood off' the printed circuit boards.
Chassis Operation and Alignment
The majority of chassis functions are implemented within
IC504 and its associated circuitry. These are controlled by
the micro-controller IC701 via the I²C bus, a two wire bus
(SDA, Serial Data and SCL, Serial Clock). The micro-
controller contains twenty adjustable parameters between
00–13 (hex) which are used to control the functions of IC504
See
. (
Adjustments
these
.)
Handling Precautions - Static Electrical Charge
The receiver contains devices which may be damaged by
static electrical charges during handling. To avoid damage,
soldering irons should be earthed, and service personnel
should, ideally, wear wrist straps earthed through a 1M ohm
resistor. If the latter is not practical, they should discharge
themselves by touching an earthed point. Sensitive static
devices should be packed in suitable conductive containers.
IMPORTANT: although the receiver chassis is isolated, the
AC supply should be disconnected during service
replacement of such static devices.
3
for further details on how to adjust or reset
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