The HP ZBook 15 G5 laptop does not booting up

[Kapha]

The HP ZBook 15 G5 laptop begins booting up with its keyboard flashing, accompanied by blinking Caps Lock and Num Lock keys, along with a loud startup sound of fans, all while the screen remains black.

[Jupitero]

Hello.

Identify the blink pattern codes with this HP Support document. If your blink code does not match any of the codes on the page or the remediation steps don't help or are not listed for the particular problem, we can continue on this message thread about further things to do.

[Kapha]

Thank you @Jupitero, the indicator blinks five times for Caps Lock and Num Lock.

And here's what I discovered:

[Jupitero · Accepted solution]

Hello again.

System board (motherboard) is the main component in your laptop that works as an interconnect for all devices in your laptop: CPU, memory, storage, graphics, keyboard - everything. One of the hundreds of components in it has produced a fault and the damage may not be visible. Repairing one would require special tools and knowhow - I cannot help you there.

The system board is replaceable but it is an expensive part. There are several system board models listed in the Maintenance and Service Guide, page 67. You could go for any model on the list, but changing from e.g. AMD to NVidia graphics (or vice versa) will also require replacing the heat sink; replacing the Core i5/i7 with Xeon (or vice versa) will also require replacing the memory modules. (all listed in the same guide)

You can either look for the part(s) yourself at parts.hp.com or seek them in Amazon and other online marketplaces. Not every possible system board may be available. You could also look out for similar Zbook 15 G5's with broken displays and buy it for the parts - or sell your old laptop for parts.

The actual system board replacement may take an hour or more even if you are a repair professional and is perhaps the trickiest thing to replace in a laptop. If you are not familiar with fixing laptops, I highly recommend taking it to a local HP Service Center and have them give you a cost estimate, order the part and do the work.

Whether it is economical to repairt this laptop is up to you of course.