HP TouchSmart 310-1033 All-in-one always has black screen, at startup I can hear fan running

310 dash what? 310-1000? it really and all-in-one PC.
what is the full model name and number.
no text? screen never ever shows any thing?

is the fan running inside, and blowing air.? it must.

the steps are here at hp.com

https://support.hp.com/us-en/product/hp-touchsmart-310-1000-desktop-pc-series/4273627/manuals

PC boot in serial progression.
power on
fan blows.
BIOS POST's with errors if found. (3 ways) beep ,text or flashing keyboard led codes.
bios text mesages, logos
windows boots.
windows login, screen
last desktop and (startup files load)
where do you land here.?

see no power? there?

Hearing fans and hard drive spin up doesn't necessarily mean system is working - just without video. If you heard a POST beep or the Windows Startup sound that would be different - and good. Is there any video on the screen at all, even just a blinking cursor in upper left of display? If not, your problem is probably hardware such as ram or motherboard. If this system has a VGA or HDMI output to connect to another monitor or TV would be a good check, but AIO system usually don't have that option. Other than that, and this is a shot in the dark: Ensure the system is off, disconnect the power plug, and hold the power button in for 30 sec for a power reset. Then plug in system and try powering it up again. If no go, you may have a hardware problem and will need a PC Tech. Hopefully it is just loose ram.

Hi Howard -
A few questions for you - When you press the Power Button, do you see and flashing LEDs? If so, which LEDs and how many times do they flash?

You can try unplugging the system from any power, hold down the power button for 30 seconds (drains all flea power) and plug it in and try. Basic move, but I've had it work several times before.

Let me know -

M

Defective Videocard onboard..

If you turn on the computer and the lights come on and the fans start but you see no picture, try turning up your volume to listen for the windows startup sound. If you hear the windows startup sound it is likely your video card or the monitor on the laptop. If you hear no sound the power could be faulty or the computer could be completely fried. Follow this link to get your laptop taken care of by HP http://h71036.www7.hp.com/hho/cache/405979-0-0-225-121.html

most PCs this old have bad RTC coin cell inside.
age:11 years old.HP retired it for support.

RTM , read the manual yet, ?

this?
https://www.manualslib.com/h/hp+iq775+service.html

Hi, you may need to do a system restore with your windows CD or try pressing the ESC button during boot up and select start in safe mode, from here you can restore your operating system to a time before the problem started. Hope this helps

sounds like hard drive gas failed

What leds you can see blinking on laptop? Can you hear any bootup sounds? Sometimes my laptop hangs on standby or hibernat, then screen is black and some leds may blink. Usually i need to take charger and battery off for 10 seconds and boot up again. If that dont help then there must be some hardware damage.