After Service Product Safety Checks - Agilent Technologies 4339B Service Manual

After Service Product Safety Checks

Whenever it appears likely that protective safety provisions have been
Warning
impaired, the apparatus shall be marked as inoperative and should be
secured against any unintended operation. The protection provisions will
have likely been compromised if, for example:
The instrument shows visible signs of damage.
The instrument fails to perform the intended measurement.
The unit has undergone prolonged storage under unfavorable conditions.
The instrument was severely stressed in transport.
Perform the following ve safety checks to verify the safety condition of the 4339B (these
checks may also be used for safety checks after troubleshooting and repair).
1. Visually inspect the interior of the instrument for any signs of abnormal internally generated
heat, such as discolored printed circuit boards and components, damaged insulation, or
evidence of arcing. Determine the cause, and repair.
2. Use an ohmmeter which can accurately measure 0.1 to check the resistance from the
instrument enclosure to the power cord's ground pin. The resistance must be less than
0.1 . Flex the power cord while making this measurement to determine if any intermittent
discontinuities exist.
3. Unplug the 4339B's power plug from the power source. Set the line switch to ON. Tie the
line and neutral pins of the power connector together and check the resistance between
them and enclosure. The minimum acceptable resistance is 5 M . Find and replace any
component which causes the instrument to fail this test.
4. Verify that the correct fuse is installed.
5. Make sure that the grounding wire (green/yellow) is secured to the chassis by a screw and
washer.
4-2 T roubleshooting