HP 840 G3 motherboard upgrade/memory issue

[d015]

My HP 840 G3 has been failing to POST intermittently with the memory error code (3 long flashes, 2 short). The problem appears and persists no matter what is done, and vanishes randomly. Re-seating everything, swapping RAM stick slots, bios updates, etc, nothing seems to be helping, although it did appear to work for a while after taking the whole laptop apart and putting it back. The RAM sticks test good, using the built-in memory tester. Since it's likely a motherboard issue, I'm wondering if there're newer replacement motherboard models that can reuse the rest of the hardware. Where can I find more information? Any suggestions related to the boot issue are welcome as well.

[Jupitero]

Hello.

Occasional problems despite everything you have done sounds very much like a system board problem. Thermal cycles may have produced a fault somewhere in some chip connector or such, hard to say.

Check the Maintenance and Service Guide for HP Elitebook 840 G3, page 72. HP has produced 5 different system boards for HP 840 G3, the only difference with them is only the CPU model. All 5 models also have two sub-models, with/without a Windows license. If you are to replace the system board with a non-licensed model, your Windows deactivates itself and will ask for a product key.

If you have already taken apart the laptop succesfully, you'll likely can replace the system board yourself as well. The guide has the required instructions for this. You can try to obtain a system board from HP Parts Store, online marketplaces such as Ebay or Amazon or ask your local HP Service center to source on for you from a distributor.