My wife's old HP (not a probook) had such and it was the indicator the main battery had failed. New battery and all fixed. It may need the CMOS battery as well.
This is NOT a sure thing. Get the service manual for your laptop to confirm.
My probook HP 440. Power on led is continually blinking and also the power cord socket led. No display coming but laptop smps fan is running. Can anyone help. Thanks

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