HP 8112A, Operating, Programming And Servicing Manual

Page: 177 / 406

1 0
l nt;roduction to Servicing
Safety
Considerations
Warning
Safety Check
Dangerous voltages, capable of causing serious personal injury, are
present in this instrument. Use extreme caution when handling, testing
an(i adjusting.
The servicing described in the following chapters is performed with the
instrument switched on and its protective covers removed. Therefore,
servicing
must
only be carried out by a skilled person, who is aware
of the hazards involved, and in ttte presence of another person who is
capable of rendering first aid and resuscitation.
Capacitors inside the instrument may still be charged after the
instrument h�s been disconnected from its external power supply
•
•
ATTENTION
Static Sensitive
The HP 81 12A contains static-sensitive devices.
Ensure that "static-safe " precautions are taken to
prevent electro-static discharge when the instrument
covers are removed.
The following safety checks must be carried out after any servicing is
completed:
1. Disconnect the power cord from the external voltage supply.
2. Inspect the interior of the instrument for any signs of abnormal
overheating or arcing, such as:
•
Discolored circuit board
•
Discolored components
•
Damaged insulation
If
a problem exists, it
must
be investigated and fixed before
proceeding.
3. Check the case to power-cord ground-pin continuity in
accordance with IEC & VDE. Flex the power cord during
the measurement to check for any intermittent discontinuity.
If a problem exists, it must be investigated and fixed before
proceeding.
4. Check the internal ground connections between circuit boards
and the instrument frame. If a problem exists, it must be
investigated and fixed before proceeding.
Introduction to Servicing 1 0-1