1. Whole screen does not work (black screen)
(1)  Check power supply
(2)  Check signal connection (cat5,DVI cable)  (synchronous screen)
(3)  If synchronous screen, check the green led of sending card and receiving card whether it is twinkling or not.
(4)  Check the monitor of PC whether it is protected as black,or screen display area is black or pure blue. (synchronous screen)

2.Whole LED module does not work(black module)
(1)  Successive modules in horizontal do not work, please check the ribbon cable between the  normal unit module and unnormal unit module whether it is connectted or not, or replace the first module from right side when facing the screen. 
(2)  Successive moudels in vertical do not work,please check the power supply of all the modules.

3.One row lamps of module does not work.
(1)  Check this row whether connecting to output pin of 4953. 
(2)  Check 138 encoder.
(3)  Check 4953.
(4)  Check Vcc and GND of 4953.
(5)  Check output of 74HC138 and 4953's controlling pin whether connectted or not.

4.Unit module doesn't work.
(1)  Check 595 normal or not.
(2)  Checking the up and down moudle corresponded common pin connect or not.
(3)  Check 595 output pin to moudle pin connect or not.

5.One color lacked in half or whole LED panel.
(1)  Check 245 R, G, B data output.
(2)  Check normal 595 output pin and unmormal 595 input pin whether it is connectted well or not.

Real and virtual-pixel screen is the corresponding.

Simply, real pixel is each LED of three red-green-blue LED which constitute a screen display is only involved in the use of an imaging pixel, in order to obtain sufficient brightness

Virtual screen is to use software algorithms to control the LED of each color to participate in the final number of adjacent pixels of the image, making the lamp with less LED to achieve greater resolution, it can increase about four times resolution.

As we all know, the largest cost is Led chip for Led display, one of our target is that we can save the cost but do not less the brightness. The virtual technology is a development direction. The virtual technology is not  a simple tube to participate in imaging, it impact much for the brightness, gray. It requires the control system coordinate with the driver chips, to use the software algorithms and driver chips to combine response time, to save the Led cost but do not less the brightness.