required safety items installed to protect users and service personnel from injury.
This guide addresses only those items. However, good judgment should be used
to identify potential safety hazards due to attachment of features or options not
covered by this inspection guide.
If any unsafe conditions are present, you must determine how serious the
apparent hazard could be and whether you can continue without first correcting
the problem.
Consider these conditions and the safety hazards they present:
• Electrical hazards, especially primary power (primary voltage on the frame can
cause serious or fatal electrical shock).
• Explosive hazards, such as a damaged CRT face or bulging capacitor
• Mechanical hazards, such as loose or missing hardware
The guide consists of a series of steps presented in a checklist. Begin the checks
with the power off, and the power cord disconnected.
Checklist:
1. Check exterior covers for damage (loose, broken, or sharp edges).
2. Power-off the computer. Disconnect the power cord.
3. Check the power cord for:
a. A third-wire ground connector in good condition. Use a meter to measure
third-wire ground continuity for 0.1 ohm or less between the external
ground pin and frame ground.
b. The power cord should be the appropriate type as specified in the parts
listings.
c. Insulation must not be frayed or worn.
4. Remove the cover.
5. Check for any obvious alterations. Use good judgment as to the safety of any
alterations.
6. Check inside the unit for any obvious unsafe conditions, such as metal filings,
contamination, water or other liquids, or signs of fire or smoke damage.
7. Check for worn, frayed, or pinched cables.
8. Check that the power-supply cover fasteners (screws or rivets) have not been
removed or tampered with.
Handling electrostatic discharge-sensitive devices
Any computer part containing transistors or integrated circuits (ICs) should be
considered sensitive to electrostatic discharge (ESD). ESD damage can occur
when there is a difference in charge between objects. Protect against ESD
damage by equalizing the charge so that the machine, the part, the work mat, and
the person handling the part are all at the same charge.
6 Lenovo Legion Y720T Hardware Maintenance Manual
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