I just fixed one JV-TV2040 monitor that worked intermittently. Turns out the AC power adapter was bad. The wire was cracked inside the strain relief where it goes into the adapter. You can either replace the adapter with a suitable replacement or do like I did and carefully hacksaw the case open, chop out about 4 inches of bad cable, and resolder to the circuit board. I glued the repaired unit back together with silicone glue.
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I just fixed one JV-TV2040 monitor that worked intermittently. Turns out the AC power adapter was bad. The wire was cracked inside the strain relief where it goes into the adapter. You can either replace the adapter with a suitable replacement or do like I did and carefully hacksaw the case open, chop out about 4 inches of bad cable, and resolder to the circuit board. I glued the repaired unit back together with silicone glue.