No matter what you do, you can't get your tablet to turn on.
It is possible that the battery is drained and needs to be recharged. Plug the tablet into the charger and wait a couple of minutes. If it still does not turn on, the battery may be dead and unable to hold a charge. In this case, you will need to replace the battery using this repair guide.
Another possibility is that the battery is fine, but the charging port is broken. The charging port can be replaced using this guide.
It is possible that it appears nothing is happening because the display is bad. In this case, the display will need to be replaced.
The audio coming from the speakers is inaudible or scratchy.
It may just be that the tablet is muted, so check to see if it is.
The volume buttons may be broken, thus, not allowing you to change the volume on your tablet. They will have to be replaced.
If there is audio coming from the speakers but it is scratchy, one or more of the speakers are broken. The broken speakers need to be replaced.
The cameras take bad pictures or don't work at all.
If either (front/back) of the cameras don't work they need to be replaced with new ones. You can find the guide to replace both the front camera and the back camera here.
The device fails to recognize a USB when one is inserted.
It could just be that the USB device you inserted is broken. To test this, try connecting a different USB device to the tablet.
If you have tried multiple USB devices, and none of them worked with the tablet, then the USB port is damaged or broken and will need to be replaced. You can find the guide to replace the USB port here.
You insert either card into the tablet but nothing happens
You may be using a card that the tablet's software can't read. Refer to the user's manual to choose a card that the tablet can recognize.
If you are using a card that the tablet can read, but it still doesn't work, you will have to replace the port.