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Problem VGA tester not work

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rho-bot

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Fix the HW design.
RGB and H/VSync signals are defined as analog signals (0,7Vss @ 75Ohm). Therefore you have to adapt the 5V PIC signals to this level. This can be achieved by putting a series resistor of 470R in each signal line (together with the 75R termination in the VGA monitor they will act as a voltage divider)
 

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Fix the HW design.
RGB and H/VSync signals are defined as analog signals (0,7Vss @ 75Ohm). Therefore you have to adapt the 5V PIC signals to this level. This can be achieved by putting a series resistor of 470R in each signal line (together with the 75R termination in the VGA monitor they will act as a voltage divider)
please share if u schematic modification.thanks before
 

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Attached you will find the modified schematic.

As the maximum current is 25mA per PortPin, maybe the PIC is already damaged by the actual circuit (5V/75R=67mA). Therefore I would recommend to change it before proceeding...
 

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Attached you will find the modified schematic.

As the maximum current is 25mA per PortPin, maybe the PIC is already damaged by the actual circuit (5V/75R=67mA). Therefore I would recommend to change it before proceeding...
yes..... my first modification to the attachment below test 3pcs VGA monitor results 2pcs OK but 1pc VGA monitor why the result rolling TEXT picture.
then use your schematic modification why the result is a text image noise vertical line.
how to cope if there is the rolling image?, what solution
thanks before
 

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rho-bot

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With my schematic you should see a fullscreen green picture, assuming the HV timing is correct.
Can you describe the results a litte more in detail? What is "rolling text picture" and what "text image noise vertical line"? Maybe you can attach a photo...
The 150R in your attachment should be removed, as the VGA monitors have a builtin 75R termination resistor at each RGB signal. But there are different definitions for the HV signals, depending of the VGA monitor interface (0.7V/5V, see here).
 

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With my schematic you should see a fullscreen green picture, assuming the HV timing is correct.
Can you describe the results a litte more in detail? What is "rolling text picture" and what "text image noise vertical line"? Maybe you can attach a photo...
The 150R in your attachment should be removed, as the VGA monitors have a builtin 75R termination resistor at each RGB signal. But there are different definitions for the HV signals, depending of the VGA monitor interface (0.7V/5V, see here).
modif resistor 150R to 75R test with 4pcs VGA monitor Result same 3pcs vga monitor OK (still image text) dan 1pc VGA monitor images text rolling (running up ):NG should appear TECT if OK, see in attachment
text image noise problem has been overcome because the input voltage Ic 7805 is too large
 

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modif resistor 150R to 75R
No, the Pulldown resistor should be removed in your schematic, it is already present in the Monitor.
Schematic should look like this:


test with 4pcs VGA monitor Result same 3pcs vga monitor OK (still image text) dan 1pc VGA monitor images text rolling (running up ):NG should appear TECT if OK, see in attachment
This sounds to me like a timing problem related to the Hsync signal. Maybe the sync pulse is too short to be recognized by this special monitor. Or there are reflections on the Hsync signal line, therefore the 470R series resistor will help.
 

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No, the Pulldown resistor should be removed in your schematic, it is already present in the Monitor.
Schematic should look like this:



This sounds to me like a timing problem related to the Hsync signal. Maybe the sync pulse is too short to be recognized by this special monitor. Or there are reflections on the Hsync signal line, therefore the 470R series resistor will help.
Thanks brother..,problem is solved and OK Now:-D
 

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Good to hear this :)
What was the problem? Have you changed the circuit according to my proposal, or have you modified the SW?
 

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