Chapter 3. General Checkout; What To Do First - Lenovo ThinkPad L420 Hardware Maintenance Manual

Chapter 3. General checkout

This chapter presents following information:
• "What to do first" on page 29
• "Checkout guide" on page 30
– "Diagnostics using PC-Doctor for DOS" on page 30
– "Lenovo ThinkVantage Toolbox" on page 33
– "FRU tests" on page 33
• "Power system checkout" on page 34
The descriptions in this chapter apply to any ThinkPad model that supports the PC-Doctor
diagnostics program. Some descriptions might not apply to your particular computer.
Before you go to the checkout guide, be sure to read the following important notes.
Important notes:
• Only certified trained personnel should service the computer.
• Before replacing any FRU, read the entire page on removing and replacing FRUs.
• When you replace FRUs, use new nylon-coated screws.
• Be extremely careful during such write operations as copying, saving, or formatting. Drives in the computer
that you are servicing sequence might have been altered. If you select an incorrect drive, data or programs
might be overwritten.
• Replace a FRU only with another FRU of the correct model. When you replace a FRU, make sure that the model
of the machine and the FRU part number are correct by referring to the FRU parts list.
• A FRU should not be replaced because of a single, unreproducible failure. Single failures can occur for a
variety of reasons that have nothing to do with a hardware defect, such as cosmic radiation, electrostatic discharge,
or software errors. Consider replacing a FRU only when a problem recurs. If you suspect that a FRU is defective,
clear the error log and run the test again. If the error does not recur, do not replace the FRU.
• Be careful not to replace a nondefective FRU.

What to do first

When you do return a FRU, you must include the following information in the parts exchange form or
parts return form that you attach to it:
1. Name and phone number of service technician
2. Date of service
3. Date on which the machine failed
4. Date of purchase
5. Failure symptoms, error codes appearing on the display, and beep symptoms
6. Procedure index and page number in which the failing FRU was detected
7. Failing FRU name and part number
8. Machine type, model number, and serial number
9. Customer's name and address
Note: During the warranty period, the customer may be responsible for repair costs if the computer damage
was caused by misuse, accident, modification, unsuitable physical or operating environment, or improper
maintenance by the customer. Following is a list of some common items that are not covered under warranty
and some symptoms that might indicate that the system was subjected to stress beyond normal use.
Before checking problems with the computer, determine whether the damage is covered under the warranty
by referring to the following list:
The following are not covered under warranty:
• LCD panel cracked from the application of excessive force or from being dropped
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for DOS
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