You can test touch screen without fully installing it onto the iPad, plugging the ribbon cable in will let the touch screen function normally if it’s not faulty.
The glass and the touch screen layer together make up the digitizer.
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The cable has dotted lines near the connector end to tell you how much the cables should be seated in the connector, it should be close to behind the line and not past it. Shouldn’t take too much effort to push the ribbon cable in fully.
You can test touch screen without fully installing it onto the iPad, plugging the ribbon cable in will let the touch screen function normally if it’s not faulty.
The glass and the touch screen layer together make up the digitizer.