HP 570-p055na does not start after power interruption during shutdown.

[Dave_Lonsdale]

Monitor (hdmi) stays black, no signal.  Monitor is OK on another system.  All PSU voltages OK (3.3, 5, 12).  PC is drawing power (approx 30W).  Ethernet port not active.  USB ports not active.

removed and replaced motherboard button cell (voltage was OK at 3.2V)

Please advise what to do next.

[Dave_Lonsdale]

I didn’t look at the screen when I pulled the plug during shutdown, perhaps it was installing an update at the time.

[savvy2]

aC power lost.

w10 not a problem mostly

fans dead you did not say PC is silent, so...

you need to learn 2 things first ,  Intel reset and long hard reset .

1: intel reset, push power button for 10 seconds and release, the intel south bridge sees that and RESETS.

2: long hard AC power reset,1,2,3,4 (not the coin cell that causes huge problems that but sure 3.3v sure is smart check.

AC power loss love to create a huge surge when it recovers, or is ligthning caused

PCs have magic protection inside call input latchup protections (aka crow bar to techs)

what happens  to the chips are the inputs are clamped, and latched up now to prevent CMOS gate destruction.

the sure is simple no AC power and get all DC caps it the PC at 0vdc. (zero volts) or below at least 0.4vdc.

doing so ends the protectors latch up mode.

do all this no USB connecting,.

once BIOS works (goal #1) you now see all setting now are wrong, many ,  coin cell pulled.

• PXE turned off in BIOS and not allowed on the boot order page/
• secure boot if active may not be,  what was there before is lost.
• if secure boot was active go to boot older and put the boot drive back to windows boot manager, as it was.

[savvy2 · Accepted solution]

no sounds told,. fans and beeps or flashing led

is the PC power light correct not amber or blinking

fans blow

dvd ejects by real button? front tray

I can not watch you nor hear it and both matter.

all  leds and sounds. and screen dead we see and means PC is dead.

windows updates can NOT stop fans, I repeat CAN NOT,

bios runs fans and if first. BIOS sceens, BIOS keeps fans running, and even the PSU has fan, some PC have 4 fans.

one on GPU ,1 case , 1PSU , 1CPU , fans matter big time in any DIAGNOSIS OF ANY DEAD PC.

just so you know.😘

[Dave_Lonsdale]

Hi Savvy2, may thanks for your quick reply.

I forgot to say that the fans are spinning normally and the disk drawer opens when pressing its button.  The pc did beep when power was reconnected but I had walked out of the room and my wife didn’t recall the detail.  I guess as you say, the first step is for the bios to function.  Unfortunately the 10s reset did not work, nor pulling the power cord for 10 minutes etc.  I will leave it unplugged for 2 hours and try again.

If this does not work, would it be possible to try the SSD from a brand new HP 290 that I have just bought or because the bios is not operating perhaps this would not help?

Please tell me what to do next.

Thanks

[Dave_Lonsdale]

PS, the power button on top of the machine switches power on and off as normal - does that use the bios?

[Dave_Lonsdale]

Good morning Savvy2

Guess what, leaving the power off overnight has solved the problem - the screen is on and Windows has started - yippee!  I must say that yesterday I was very sceptical it would be successful.

Very many thanks for your help, I will now check to see if anything has been corrupted.