Samsung Syncmaster S23A550H no video on VGA

[budm]

Re: Samsung Syncmaster S23A550H no video on VGA

If the monitor does not detect signal from PC, it will go into standby mode, that is why I have you check and see if the signal lines are shorted to ground or not. i believe right now the video processing circuit is not seeing the VGA signal from the VGA port.

[tibimakai]

Re: Samsung Syncmaster S23A550H no video on VGA

Removed the diodes and tested them and they are all good.
The monitor still doesn't run without them. Must be something else.
Why would the backlight turn off when the VGA is plugged in?

[budm]

Re: Samsung Syncmaster S23A550H no video on VGA

The monitor will still work without the Diodes, so you can remove the suspect diode one at at time to see if it VGA will work. The 75 Ohm may be the termination resistors for the Red, Green, and Blue signal lines (pin 1, 2, 3) that you can see in the diagram.

[tibimakai]

Re: Samsung Syncmaster S23A550H no video on VGA

It looks very similar.
There are three double diodes(like a SMD transistor) and two double zenner diodes(same as the other three).
The zenners look good, but the three diodes between two legs show 75.5 Ohm on all three diodes.
All three could be bad? Or should I remove them and check again.
On the HDMI side they show as I would expect to show a good diode.
Camera battery is charging now.

[budm]

Re: Samsung Syncmaster S23A550H no video on VGA

You can use Ohm mode to look for shorted out Diode since we are looking for low resistance, when semiconductor shorted out it will be just like low value resistor (low ohm reading both ways).
As you can see in the sample in the PDF, the Diodes have one leg connected to ground (see if your monitor uses the same setup), so you can use Ohm meter between the Ground and check each as shown in the Diagram to see if one of those signal pin is shorted to ground.
Per diagram, the protections Diodes are on pin 1, 2, 3, 5, 9, 12, and 15.

[tibimakai]

Re: Samsung Syncmaster S23A550H no video on VGA

There are three double diodes and two double zenners behind the D-Sub connector.The diodes are MFW15 and the zenners are KZ4 Y6.
On the diodes I measure on one pin 4.99Z and )V on the other two pins.
On the zenners on both double pins are )V and on the single pin side on one zenner is 0V and on the other I measure between 0.34-0.7V.
Not sure what should I check.
Those three double diodes, if I check with the diode checker one side shows on all three 0.5V and the other side 0.075V and beeps.
The zenners shows exactly the same as on the HDMI side. The diodes are not showing the same readings.
In the next hour I will post some pictures.

[budm]

Re: Samsung Syncmaster S23A550H no video on VGA

I would check the protection diodes for each signal pins around the VGA connector.
See PDF for example.

[tibimakai]

I have got this monitor from my work place, since it would not work with a VGA signal.
They didn't test it out with other inputs, but I have tried it out with an HDMI signal and the monitor works.
It tries to switch to analog, but then the picture becomes black, even the backlight turns off.
It seems that the analog signal doesn't work, but the digital it works.
What could it be the problem with it.
It has the latest firmware, at least the software that what is states when I try to install it.