You've now had multiple confirmations that the system board is faulty.  

On a three year old budget system, carefully consider the cost of a board replacement (with likely at best a 90 day warranty) against the cost of a new system, with at least a 1-year warranty.

Once a system reaches three years old, system replacement is usually the more cost-effective option.

I had given it to a local repair shop. They made it switch on. But it is still getting stuck at logo. He also said motherboard replacement is only option. I got a quote from Dell for the same, but the service centers don't confirm the same. Also, if other local repair shop confirms that it is motherboard issue only, whether dell sends the motherboard and technician at home. I was suggested this by one of the service centers. Typing from mobile and in a rush. Do help .

But now it is starting and even f2 , f12 can be pressed. The problem is that dell is telling me a price for motherboard, but the service center is not confirming the price and also charging a bigger amount for diagnostics. Dell should have their own service centers. Also, heard that dell can sell me part directly and send a technician at home. If I had used the system for 3 years, I would have forgot it. For a year, I used it almost once in 2 months. Then the next 2 years I started using it more slowly. I want to get this sorted as don't want to have a bad experience and remember my worst experience with Dell always. Just fell should help me by understanding the things mentioned above.

Exchange it for an older dell laptop by paying some money. Will buy a newer one soon. Happy that Dell charges lesser than other companies for motherboard replacement. I will want Dell to help me by telling tips to avoid such motherboard issues in future, and also a special discount coupon as because of this I have to switch to a old laptop and need to buy new one.

I'm sorry to be this way, but you are at the point where you need to throw that computer out and buy another one. In my humble opinion, don't buy another Dell! Dell laptops are junk now (look at any reviews) -- not sure what happened with the company, but at this point I would never purchase a Dell branded laptop. HP, by the way, is in the same bad shape. Lenovo is still getting good reviews.

My son's computer started doing the same thing you describe just after the warranty expired. Many hours spent troubleshooting, only to finally realize what a piece of $850 junk Dell sold us.

The main cause of the Dell black screen issue is a bad connection between your graphics drivers and your operating system. Another possible cause is a display adapter driver update issue. You may also run into a Black Screen of Death after system updates or installations, which you may need a reinstallation of Windows