Lenovo c40-05 Posting Troubles

[hippiejenrose]

I purchased a new Lenovo C40-05 last year. I have gotten maybe 3 months total use out of it. I have had to have the motherboard replaced twice. The first time it was replaced by my warranty by a professional technician. When I picked it up I forgot my power supply at home so they used theirs and the machine ran around 20 minutes with no issues. When I got it home I plugged it up and began installing a new operating system. It lasted about 10 minutes and stopped posting. After repeated phone calls to Lenovo they finally agreed to send a tech to my home to repair it. The tech determined it was the motherboard again. Again it was replaced. This was just days before the expiration of my warranty. Within 5 to 10 minutes of the tech leaving it occurred again. Now I'm left with a 600 dollar paper weight.
The computer comes, on the power button lights up, but the screen remains black. There is a small button near the power button that when pushed brings up a timer on the screen which leads me to believe that there is nothing wrong with the monitor. It wont post or do anything else for that matter. Once its on the only way to turn it off is to unplug it. It cant be powered down in any of the normal ways like holding the power button down.
What I'm asking is what could the problem be. The computer is still basically new. I'm at a loss as to what to do with it. I don't want to throw good money after bad.
Here are the specs: https://www.cnet.com/products/lenovo-c40-05-all-in-one-a4-6210-1-8-ghz-4-gb-500-gb-led-21-5/specs/ . If anyone has any ideas please let me know. I'm at my wits end.

Thank you in advance for any advice that anyone has.

 

[hang-the-9]

If the motherboard was replaced, maybe it's the power supply. Really this is why all-in-ones are a bad idea, you combine the worst features of a laptop and a desktop without a lot of benefit. If the issue happened again right after the tech left, what did Lenovo do? They should have swapped your unit out at this point or tried something else.