Failure analysis and maintenance for LED unit board ?
A. All board is not bright,
1. Check power supply and signal lines if connect well.
2. Check if test card identify the interface.
3. Check 74HC245 with or without virtual welding short-circuit
4. Signal input and output feet on 245 if virtual welding or short circuit to other lines.
B. A line or lines are not bright.
1. Check 138 to 4953 circuit if have open circuit, virtual welding or short circuit.
2. Find control pin of this line,
C. There is a single point or multi-point (irregular) is not bright.
1. To find module corresponding control foot measurement If happen short circuit with its line.
2. Replace the module or single lamp.To check whether connect with driver IC output.
D. With a single point or single highlighted, Or entire line highlighted, but not be controlled.
1. Check whether the line connect with the power or short circuit.
2. To test whether this link short circuit with positive pole.
3. Replace the driver IC.
E. Display chaos, but output signal is normal to next board.
1. Test 245 corresponding STB Latched output if connect IC Latch end, or signal is short circuit
to the other line.Other situation,display chaos, output is still not normal. There are other ways to check it.
2. Testing the clock CLK latch and STB signal is short circuit.
3. Check If there is a input/output from 245 clock CLK.
4. Test the clock signal if short circuit to other line.
Notes: Main testing the clock and the latch signal is OK.
F. Show lack of color.
1. Check whether color data of 245 have input and output.
2. Check color data signal if short circuit to other line.
3. Check color data signal’s concatenation data port if open circuit , short circuit or virtual welding
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