HP All-in-One 24-f0066 - 3 beeps followed by 4 beeps

[plb2000]

According to the HP beep code page:

Hardware

3.4

The system board displays a power failure (crowbar).*

Indicates potential power system failure.

1. Reduce to minimum config (CPU, System board, PSU, 1 DIMM of memory) and isolate failed component.
2. Reduce further if issue persists.
3. Test known good PSU.
4. Replace affected component.
5. If unable to confirm source, replace CPU, System Board, PSU.

However, the All-In-One unit uses an external power brick and no internet PSU.  I have used 3 separate bricks and they all result in the same 3.4 beeps.  I have removed everything from the motherboard except the CPU fan and the speakers yet still 3.4 beeps.  When I completely remove the memory I end up with the:

Hardware

3.2

The embedded controller has timed out waiting for BIOS to return from memory initialization.

Indicates potential memory failure.

1. Reseat memory.
2. Correct memory configuration (correct DIMM placement and size/type matching).
3. Test with known good memory.
4. Replace affected component.

Since this is an All-In-One where should I go from here?  There is nothing obvious I should do.

[Hibb1]

Do you have one memory module or two?
If you have two, try one at a time.

Otherwise, I'd say your mainboard is dead. 😞

[plb2000]

I have two memory modules, 4GB each and I have moved them around between the slots together and individually and this has changed nothing.  So, I purchased a known good replacement motherboard and I still get the exact same beeps.  Any other ideas?  Maybe I need to try all new memory?

[Hibb1]

Weird... Doubtful that BOTH ram sticks are faulty, Also doubtful that an Intel CPU is faulty. DId you get any kind of power surge prior to the unit failing? If you did, that could have blown the CPU and RAM. I've had a power surge kill a dual xeon cpu setup.

Also are you using a HP branded 65w power adapter?

Also check there are no bent pins in the CPU socket. I seen it before where you just get POST beeps when there's a bent pin.