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5. FAULT FINDING AND RECALIBRATION
5.1 Fault Finding
In general, faults in attenuators are due to input
levels in excess of the rated maximum or dirty
switch contacts. If the location of the fault
does not become apparent following avisual
inspection, then proceed as follows, using a
suitable oscillator and level measuring instru-
ment:
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With all the controls set to 'OdB' ,check that a
'through' balanced signal can be obtained. This
will indicate that the input/output wiring and the
'bridging' switches are in circuit and functioning
correctly.
Check each step of the four attenuator sections in
turn, and each whole section against astep of the
following section until the fault condition is
shown.
If resistors are at fault they must be replaced by
the types specified in the Parts Lists at the rear
of this manual.
5.2 Recalibration
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If the fault proves to be more than just asimple
replacement of aresistor or the cleaning of
switch contacts, then the attenuator should be
checked against a'standard' unit and the tests
called for in the manufacturing specification
carried out. It is strongly recommended that
recalibration be carried out by the Service Dept.
of Wandel &Goltennann Ltd. or an approved organi-
sation appointed for this purpose. 5-1
