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Top Student
Posts: 7
Member Since: ‎03-19-2010
Message 1 of 3 (2,954 Views)

CQ40-505LA: Black Screen and CMOS issue, laptop not starting

Hi Community,


I recently acquired a notebook (4 months) CQ40-505LA and it stopped working. When I “power on” the laptop it only shows a black screen with no information, neither the usual check CMOS messages. The “caps-lock” and “num-lock” led gets blinking. Only once or a couple of times it gave an error message: .. “The CMOS checksum is invalid. The CMOS will reset”


This problem started last week when the laptop was running and suddenly stopped working with the black screen mentioned and no error messages displayed.


I will really appreciate any suggestion to fix the issue or troubleshoot the problem.


An additional question is:  it seems that these new laptops do not have a CMOS battery, that usually where the cause when the CMOS were failing. Is this right? I couldn’t find in the manuals where a CMOS battery could be located for this laptop.






For reference of this laptop model , this is the HP link:

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Grad Student
Posts: 286
Member Since: ‎02-10-2010
Message 2 of 3 (2,937 Views)

Re: CQ40-505LA: Black Screen and CMOS issue, laptop not starting

[ Edited ]

Hi Carlos2000HP, I don't know if your laptop has a CMOS battery, but have you researched blink codes?


Your pc could be telling you something; read this  document fully.


Good luck, and reply back with your progress, please.

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Top Student
Posts: 7
Member Since: ‎03-19-2010
Message 3 of 3 (2,905 Views)

Re: CQ40-505LA: Black Screen and CMOS issue, laptop not starting

Hi compenthusiast,


Thanks for taking the time to answer, I followed the advice but I have not succeeded, I checked for the blink codes, but the laptop keeps blinking the “caps-lock/num-lock” led continuously with no stops, so I cannot match the blink with any code in table (they go from 1 to 6 blinking in the table for the caps-lock/num-lock). The only noise I can hear for a while is the fan cooler and stops a fewer seconds after I power on the laptop.


The other option I tried was to do a “bios hard reset” by taking the battery out, disconnecting the AC Power and pushing down the power button for 20 seconds as indicated in the troubleshooting.


Also y took out the RAM memory module and inserted again just to check In any case thanks for the advice!, If you think there could be other options to try, please let me know and see how to get the BIOS back.


Regards, Carlos.

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