Chapter 3. General Checkout - Lenovo ThinkPad T420i Hardware Maintenance Manual

Chapter 3. General checkout

This chapter presents the following information:
• "What to do first" on page 28
• "Checkout guide" on page 29
- "System supporting the Lenovo ThinkVantage Toolbox program and the PC-Doctor for DOS
diagnostics program" on page 29
- "System supporting the Lenovo diagnostics programs" on page 33
• "Power system checkout" on page 37
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, it is recommended to 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.
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