Wednesday, September 6, 2017

new display monitor

Only a while ago I wanted to update one of the two 1920x1200 LCD monitors for my Windows 7 PC to a Samsung 4k monitor. I ran into the problem with the new graphic expansion card. I decided to call off the upgrade and live with the two 1920x1200 Dell monitors.

Both of these monitors are between 10 to 15 years old and has cold cathode florescent backlight. The older of the two has became quite dim as well as spectrum shift to color temperature that is too low. Still I use it as the secondary (off axis) monitor. Recently one day when I woke the computer from sleep the resolution dropped to 1024x768. I swapped the DVI I cables and the connections to the graphic card and the XGA resolution remains with the same monitor. If I force the Windows OS to re-detect the monitors, the monitor would disappear (drops off).

I knew right away the problem must lies with the DDC signals. It has been so long that I think about DVI interface I struggled to remember if the DDC is imbedded into the LVDS video signal pairs. This is important as if the DDC signals are dedicated, it is consistent with the symptoms. My suspicion is the one of the two DDC lines must become marginal either in voltage level, or timing. I really do not feel like opening up the monitor and try to trouble shoot it given how old it is. However despite these two monitors are so old, today only very few monitors are made in 1920x1200. You can pick up a 1920x1080 monitor for next to nothing, but if you are like me, insist on 1920x1200 you have to pay a premium for one made by Dell. Additionally both of these monitors are ISP (in plant switching) type LCDs.

I then realize I can confirm my suspicion without trying to debug the monitor by opening it. I can use the VGA interface. I know the DDC signals for the VGA interface is likely another pair of signals not sharing with that in the DVI interface. A very good chance the VGA interface is usable. I turned the house upside down to look for a DVI to VGA adapter. I knew while such an adapter is obsolete I would have kept one for the rainy days event like this.

Found one I did, as well as a VGA cable. I substitute them in place of the DVI cable and bingo the monitor is once again 1920x1200. There is no discernible display artifact. A week would go by and I was happy to have both monitors.

A few days ago I came across a number of labor day deals on Arstechnica. Among the discounted items is a 24-inch 1920x1200 Dell ISP monitor, for just $179. It is a no-brainer and I immediately order one seeing it has DVI, VGA, and Display Port interfaces. Of course it has LED backlight. A few days later it arrived, and I immediately set it up. It is so much lighter and slightly thinner than the old Dell display it replaces.

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