Tab 4 shows a black screen with vertical lines

My son's Samsung Tab 4 (7") was left out on an enclosed screen porch. It rained that night, but not directly on the tablet. Perhaps it was affected by the air's severe moisture and humidity? My husband replaced the digitizer, and that did not solve the problem. The tablet makes normal sounds and the touchscreen still works. We just cannot see anything but the black screen with lines. Is there another part that we can try to replace to fix the problem?