In all likelihood if you have used the printer for > 3 to 4 months the LCD shutter has failed; though such failures are not usually as complete as you describe, however it is the first thing I'd check.
Remove the resin vat and platen assembly, a perform a dry-run "printing" of this file--
LCDTest.stl (1.3 kB). You will have to use Chitubox to slice it and save to a
.cbddlp or
.ctb file.
The
LCDTest.stl file defines a 120 x 68 x 2 mm solid block:
Placed a sheet of white paper over the LCD, and when "printed" in a dry run the LCD should display a relatively bright "white" 120 x 68 mm rectangle:
But more likely with a one-ear-old printer you will see a dim rectangle, or one marred by numerous dark spots caused by dead pixels and clusters of pixels in the LCD.
This is what mine looked like after just 3 months (300 hours or so) of operation:
If possible post some photos of what you see...
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Note: the built-in "exposure test" if just that, an exposure test--it is not a test of the complete LCD (it escapes me why such an onboard test is not available) , it "prints" a 10 x 68 mm frame around a solid central rectangle. The LCD can be in pretty bad shape and still look OK with the exposure test. Here's a shot of the exposure test using the same bad LCD as shown above:
The major flaw is visible once you know it's there, but the overall failure of the LCD is not "in your face"--and a bad LCD, one just dimmed overall, would appear to be fine to an inexperienced user.