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Always Full Speed Fan Runing after restart of my Z400

HP Recommended
Microsoft Windows 10 (64-bit)

Hello.   I have an issue about "Z400 does not start windows 10 launching" ONLY after restarting.
Only after restarting.  When I have this issue, I switch power supply off and press power switch on.  Then my z400 goes to launch properly.

Symptom is like this:

1. I am working on Z400 as usual.

2. Sometime I need to restart Z400 , for example, after updating windows 10 etc.

3. Z400 can turn off to stop running properly.

4. But when it comes for Restarting, Z400 fails and maybe CPU fan runs at full speed.

5. So Z400 won't launch any.  Display shows black screen.  Only fan runs at full speed.

6.  Nothing changes even waiting long time.

7.  So I switch power supply button off.

8. a few second I turn on the power supply button.

9.  Then Z400 launches windows 10 properly.


What do you think of this issue and can you show any ideas if I may ask?

My Z400's spec:  Xeon W3520 2.67GHz.  10GB Ram, Windows 10 Pro v1909

Graphic card GTX660.  Power supply watt is original 475W.

I suppose there must be some setting tweak will recover this issue.  But I could not find good solution so far.
Please lend a hand!


Level 12
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I would look at the power supply first.


High speed fans and no peripheral action such as the keyboard and mouse suggests either the power supply or a motherboard problem.


Have you tried reducing the PC to a minimum configuration?





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