Lenovo E470 Hardware Maintenance Manual

Also see for 20H4: User guide

Power system checkoutTo verify a power symptom, do the following:1. Turn off the computer.2. Connect the ac power adapter.3. Turn on the computer. If the computer can be turned on, it means that either the battery pack or the acpower adapter is functional.4. Insert a straightened paper clip into the emergency reset hole to reset the computer. If the computer isstill powered on, it means that the ac power adapter is functional.5. Turn off the computer.6. Disconnect the ac power adapter and turn on the computer. If the computer can be turned on, it meansthat the battery pack is functional.If you suspect a power problem, see the appropriate one of the following power supply checkouts:• “Checking the ac power adapter” on page 29• “Checking the built-in battery and operational charging” on page 29• “Checking the coin-cell battery” on page 30Checking the ac power adapterYou are here because the computer fails only when the ac power adapter is used.• If the power problem occurs only when the docking station or the port replicator is used, replace thedocking station or the port replicator.• If the system status indficator does not blink three times when an ac power source is connected, checkthe power cord of the ac power adapter for correct continuity and installation.• If the computer does not charge during operation, go to “Checking the built-in battery and operationalcharging” on page 29.To check the ac power adapter, do the following:1. Unplug the ac power adapter cable from the computer.2. Measure the output voltage at the plug of the ac power adapter cable. See the following illustration:(20V)132Pin Voltage (V dc)1 +202 03 GroundNote: Output voltage of pin 2 of the ac power adapter might differ from the one you are servicing.3. If the voltage is not correct, replace the ac power adapter.4. If the voltage is acceptable, replace the system board.Note: Noise from the ac power adapter does not always indicate a defect.Checking the built-in battery and operational chargingThis computer supports only batteries specially designed for this specific system and manufactured byLenovo or an authorized builder. The system does not support unauthorized batteries or batteries designedfor other systems. If an unauthorized battery or a battery designed for another systems is installed, thesystem will not charge.Chapter 3. General checkout 29