All in one stuck on logo screen and inability to access the BIOS

[virtualzeta]

Hi! I was given a computer to repair that wouldn't start. I restored the OS on the PC and used it for 3/4 days, keeping it turned on 24 hours a day and doing several reboots.

Performed comprehensive diagnostic testing of the system outside of Windows and no errors were present.
Performed disk checks and defragmentation (not even necessary as it is already OK) in Windows.

Everything worked even if it wasn't fast and some updates gave some problems but by retrying several times we moved forward. After yet another post-update reboot, it hangs on the words "Restarting" (without hourglass) and the mouse pointer is visible but blocked. I waited about 30 minutes but I already understood that it wasn't like the times I had to wait up to an hour for it to restart (with hourglass present).

From that moment on every time I turn on the HP logo appears but nothing else can be done and no function keys access the BIOS, diagnostics or anything else.

Years earlier, HP customer service replaced the motherboard due to a problem with code SYSE01 ("Can't power on") with a spare part ASSY MBD Crane4G SKL MesoXT BC (now apparently unobtainable).

HP Pavilion All-in-One - 27-n200nl
T1H23EA
Windows 10 64bit

Tested operations:

- fast repeated pressing of the ESC, F1, F2, F8, F9, F10, DELETE, BASKSPACE keys (and all the other functions keys) does not activate/open anything at startup;

- pressing WIN + B, WIN + V, B, or V, at startup (pressed and held down before and after turning on for over a minute) to start BIOS recovery from HDD but it does nothing;

- pressing WIN + B, WIN + V, B, or V, at startup (pressed and held down before and after turning on for over a minute) to start BIOS recovery from USB flash but it does nothing;

- pressing CTRL + ESCAPE at startup (by holding down or repeatedly) but it does nothing;

- disconnect all components (HDD, M.2 WiFi module, speakers, webcam, keyboard, mouse, etc.) and CMOS battery, except RAM (without it there are beeps) and converter board (if disconnected the LED power button flashes and the computer does not turn on) without any result or warning of peripheral failure;
- use all combinations of the two RAM modules (RAM #1 in slot # and RAM #2 in slot #2, RAM #2 in slot #1, RAM #1 in slot #2, RAM #1 in slot #1, RAM #1 in slot #2, RAM #2, in slot #1, RAM #2 in slot #2);

- changed the CMOS battery (still quite charged) with a new one (more charged);

- tested wireless and wired keyboard both in rear and lower USB;
- clean and degreased motherboard on both sides;
- waited a night with the computer unplugged and the power supply unplugged.

Nothing I have done has produced the slightest result. Only and always the HP logo.

Thanks for any help/advice.

[WAWood]

You realize, I am sure, that from here, with no access to the PC, all we can do is GUESS -- and my guess, based on what you have said and done, is that the motherboard has failed.  If it was just the drive, or the windows install, you could go into the BIOS and run diagnostics -- which you did, earlier.  But now, you say that you can not even do that.  You could try a different keyboard on the wild chance the keyboard has gone bad, but my guess is that will make no difference.

You mentioned the motherboard was replaced already -- so to me, it looks like the second one has failed, now.

[virtualzeta]

First of all, thanks for the reply and your opinion.

It's clear that we can only make assumptions here, as with any other post, and these are precisely the reasonings I'm looking for.

I have already tried two wired keyboards and one wireless one from HP.

Although I also tend to think that it is the motherboard, I would like to be able to consider other hypotheses, because unfortunately it is not possible to find that card on the market or as a used one. Furthermore, there are particular cases in which the bump on the HP logo is not necessarily linked to a motherboard failure and I try to understand, with the advice of those who have had experience, whether there could be another cause.

Furthermore, I would add with respect to what was said before, that before handing over the computer to me it was in a service center for months where they had assumed it was the motherboard but they couldn't find it and they returned everything to the customer without having done anything.

I'm talking about a non-HP repair center and it has nothing to do with the replacement of the card from years ago.

If the technicians before me had managed to enter the BIOS they would have done everything I did subsequently BUT perhaps they were not able to do it. But that's just my guess because, from what I know, they haven't really gotten into WIndows.

So perhaps this situation in which I find myself now was already present in the past but can be overcome in some way that I cannot understand. Maybe it's a problem that sometimes occurs and sometimes doesn't, which is obviously always a problem because it can't work like that.

Even though it seems strange to me, I also thought it could be the external power supply and that's why I kept everything turned off for at least one night. After all, when I turned it on, it certainly hadn't been turned on for a long time and it could have been a discriminator, although not that likely.

When the computer arrived to me the first time I turned it on it was in this situation BUT after keeping it on for a while the screen went black (overcoming the logo freeze condition). Since this happened after about 30/60 minutes I didn't see if anything else appeared but this certainly isn't something that has happened again. The next time I restarted the computer I was able to access the diagnostics, something I hadn't even tried to do before because I wanted to see what it did without intervening.

In essence, although the card had been changed years before (but due to a failure to turn on and the logo not being blocked) and it didn't even start, in the last few days the computer turned on anyway and remained on constantly for 24 hours a day and then only stopped during yet another reboot. (although it was slow).

So something makes me think that maybe this fluctuating situation I can post to another answer. Furthermore, the fact that the motherboard has been changed could also be seen from a different perspective: that is, being "new" it would perhaps be difficult for the same bad luck to happen to it, without pretending that this is necessarily the case.

What I notice is:

- I see the HP logo;
- when I turn off the power without turning it off it recognizes the state of power cut and when I reconnect the cable it turns on by itself;
- if I remove the RAM it emits beeps;
- if I remove the converter board the light flashes and does not come on;

so it would seem that the BIOS is doing its job and works but then it is unable to manage its boot sequence which is stored outside in volatile memory which should MAYBE be inside the southbridge, and if even disconnecting and reconnecting the battery it doesn't work then perhaps it's really the motherboard.

Yet it could perhaps be something else, given that every computer reacts differently even in the same conditions.

For example, could it be that the processor that in the end was no longer there because I noticed that sometimes it gets very hot when I try to turn it on and the fan starts at full speed even though only the HP logo is present? Maybe he came back to life for a short while and then died permanently. That one can easily be found at a low price and honestly I have already ordered it to try.

I would expect the computer's BIOS to tell me that the processor is not working, but maybe that's not how it's supposed to go in this case.

[virtualzeta]

In the meantime:

- I tested the CPU socket (LGA 1151) with an LED device that checks that the connections with the northbridge are also working and the result was positive;
- I tried a new Intel Core I5-6400T SR2L1 2.2GHz processor but nothing changed;
- I continued to look for the motherboard (828620-606 DAN61AMB6F0) but I can't find the exact model but only compatible ones (with different or absent microphone and webcam connectors).