HP EliteBook 850 G4 Maintenance And Service Manual page 114

NOTE: Refer to battery replacement section
for removing/replacing the battery
The sections below are intended for authorized service providers/technicians.
NOTE: 2015 mWS does not have the power
cable between system board and power
connector on chassis
102 Chapter 8 Troubleshooting guide
● Check power light (7. Status lights, blinking light codes, troubleshooting lights,
and POST error messages on page
to the computer is good.
Verify battery condition/status
1. Check battery condition (overall result, cycle life, voltage, etc.) using HP PC
Hardware Diagnostics (UEFI) or HPSA tools.
2. Verify that battery is installed properly in battery bay without a gap and that
latch locks are tight (for models with removable batteries).
3. Check battery status light
lights, and POST error messages on page
discharged, preventing system from booting.
4. Determine whether the computer can turn on with battery only.
5. Remove service door and test with a verified working battery. If the computer
boots, inspect original battery before replacement.
6. Test battery with a verified working computer to verify that it is OK.
7. If there is still no boot, remove battery and boot on AC power only.
Verify AC adapter – voltage
1. Measure DC voltage output that should be around 19.5 VDC and acceptable
voltage range is from 18.5 – 20.5 VDC.
2. If the DC voltage is out of range, replace the AC adapter.
NOTE: This action requires a digital voltmeter.
Verify power button, power connector
1. Be sure that power button is not stuck.
2. Reseat power connector cable (if applicable).
3. Replace new power connector cable (if the cable exists and is defective)
4. To isolate faulty power connector cable and power button, technicians can short
power-on pads/pins to power up the computer. Contact HP Engineering for this
information.
Verify blinking lights (7. Status lights, blinking light codes, troubleshooting lights,
and POST error messages on page
At this point, there should be sufficient power from the AC adapter to the system
board. Expect to hear the fan spinning and see blinking lights or error messages (i.e.,
faulty memory, HDD, etc)
Verify Power Good (Troubleshooting) lights
1. Verify if the system board has power-on issue related. If there is no power-on
issue, move to next steps. For more information, see
(Troubleshooting) lights on page
2. Verify all connections and reseat parts
on page 96).
Verify system board
1. Test essential hardware configuration
on page 97, 12. Test with verified working configuration (hardware and/or
92). Rear power light indicates external power
(7. Status lights, blinking light codes, troubleshooting
92). Be sure that battery is not fully
92)
Power Good
94.
(10. Reseat cables and connections
(11. Test with minimum configuration