I have managed to brick my old low end android phone which is a Spreadtrum SC6820
device and now Im trying to unbrick it.The phone vibrates infinitely when switched ON or plugged into a USB port showing nothing on the screen,this behavior started when I aborted a wrong fastboot flash operation in the middle(fastboot flash system recovery.img).
After this I erased the partitions and flashed them correctly(using the .imgs from the internet) but the problem is still the same ever since ,as per one point I saw in your forum the battery is charged enough so this is necessarily a corrupted OS situation here.
Next I tried ResearchDownload.exe flashing utility but the phone starts buzzing as soon as it is plugged in the USB and is never responsive to the tool.
After installation of the drivers I can find the directory but there is no adb_usb.ini in there,I followed the direction mentioned in Setup ADB and the step was finished successfully(I can still see the "windows driver package - google inc. (winusb) androidusbdeviceclass" from prior installtion in the installed programs list and also can connect to the phone in Fastboot mode).
In point 7,I chose SciU2S.inf and then hit install which shows SCI Android USB TO Serial(com 3) with exclamation on it and google-usb_driver installation just gave me "Data of this type not supported"..