Hi Raguraman! This may have been a cooperate laptop that was issued to the education sector. However! There is a way around the problem. If you press (Ctrl +d) twice and enter into developer mode. The chromebook will refresh the system back to how it was when new, taking to the (welcome) splash screen. DO_NOT_UNPLUG the mains or switch it off, otherwise this will corrupt the system, rendering the machine SERVICEABLE! You will need to press (Ctrl + Alt + Shift + r) once in the welcome screen to delete any BIOS passwords, the system will prompt you again, as it goes through a full power-wash, press the continue key, and after a few minutes the Chromebook will reset…

Upgrading ACER-c720 Chromebook on-board system memory! If your machine has only 2GB of system memory on-board, you can have an engineer flow the empty spaces with more memory allowing the system to reach the maximum of 4GB, However, this can be achieved by you if you have electronic skills. I purchased a dead mother board from eBay, found that the video card had failed, so I replaced the SMD component with a 2nd hand part from another Motherboard using a hot air gun, and it worked fine, the same applies to adding memory . Although, these components are not necessarily replaceable. This is just a myth, in order for the customer to buy a new Chromebook. The whole re-work procedure should take no-longer than 5-minutes to complete. See (you-tube) videos on replacing 2nd-hand SMD components! ONE NOTE to point out is, if you do change or upgrade the Motherboard, you may have to re-install the Operating System from an SD-card back to the SSD. You could also upgrade the SSD to 32, 64 or 128GB giving you ample...

The reason behind this is, that the laptops circuitry diverts all the ampere from the USB back to the main CPU when the lid is open (back from standby mode). If however, you laptop has a USB3.0 port, then there shouldn’t be a problem as these 3.0 ports can deliver upto 1.25 amps enough to power or charge any iPhone on the market.

Are you receiving any sound using headphones? If not, then it could be that a dry joint has occurred at the socket on the circuit-board! this is very common with low end laptops. You’ll need to take out the motherboard to do some basic tests. If you don’t have a multi-meter handy, then using a magnifying lens, you should see what is known as a dry-joint, which resembles a dull and crusty joint. They should be shiny in appearance. But before resorting to the latter, try un-plugging the speaker lead from the board first, this can be found on the right hand side and has 3-wires. Then re-insert the connector. Sometimes, that’s all it takes as static build-up (ESD) can often play a part. If all the above steps don’t work, then it’s the SMD chip-on-board is the culprit, that will have to re-flowed by a computer expert.

Try re-connecting the video cable on the motherboard and at the back of the display. NOTE:- You will need to take apart the machine to do this. But, at your own risk. See “YouTube” videos for this, if you are unsure of the dismantling procedure. If you do this, and it still plays up, then you need a new “video” cable… There are plenty to be had on eBay! Hope this helps?

Have you tried going into settings/sound and checking to see if it is switched on?