After Service Product Safety Checks - Agilent Technologies 4284A Service Manual

3-4. AFTER SERVICE PRODUCT SAFETY CHECKS

WHENEVER I T APPEARS LIKELY THAT PROTECTIVE SAFETY PROVISIONS
HAVE BEEN IMPAIRED, THE APPARATUS SHALL BE MARKED AS INOPERATIVE
AND SHOULD BE SECURED AGAINST ANY UNINTENDED OPERATION. T H E
PROTECTION PROVISIONS WILL HAVE LIKELY BEEN COMPROMISED IF, FOR
EXAMPLE:
INSTRUMENT SHOWS VISIBLE 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 five checks to verify the 4284A's safety (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, s u c h a s discolored printed circuit boards a n d components,
damaged insulation, or evidence of arcing. Determine the cause and repair.
2. Use an ohmmeter which can accurately measure 0.5 n to check the resistance
from the instrument enclosure t o the power cord's ground pin. T h e resistance
must be less than 0.5 S2. Flex the power cord while making this measurement to
determine if any intermittent discontinuities exist.
3. Check the GUARD terminal on the front panel using the procedure outlined in step
2.
4. Unplug the 4284A's power plug from the power source. S e t the power switch to
ON. Ti e the line and neutral pins of the power connector together and check the
resistance between them and the instrument's enclosure. The minimum acceptable
resistance is 2 M . Find and replace any component which causes the instrument
to fail this test.
5. Verify that the correct fuse is installed.
WARNING I
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