Question about ViewSonic G70fmb (Black) 17" CRT Monitor
I've had a Viewsonic G70fmb graphic monitor for a while. It's really been a wonderful CRT monitor...extra-fine .21 dot pitch.
Suddenly, it has lost the ability to display the color red. Naturally, all the colors now no longer display properly, though the monitor itself otherwise works fine. Any ideas? I could take it apart and fix something, if I new what to look for.
If you think that electronic repair is very difficult to learn then you have to read this article where only by using a solder gun could solve a Monitor color problem. Of course there were many tough dog cases (very difficult to find out the fault) in electronic repair but at the same time there were also many cases that can be solve by some simple ways. This G70fmb Monitor came in with no blue color problem. How do I know if the blue color was missing? Simply run a color test (that you may also download from the internet) or from a Monitor testing program generator, you could clearly see as which of the color is missing when you run the color bar test.
A missing blue color in the Monitor could cause the display to turn yellowish. Troubleshooting color problem is one of the easiest in Monitor repairing. Whether the missing color is from blue, red or green there are some areas that you need to check in order to successfully repair it. Here are some of the points that you need to check:
- A bended color pin at the VGA connector. (If pin one is bend then there would be no red color)
- A defective VGA signal cable. If the internal wires were broken then there would be missing colors. You can check if the signal cable is good or bad by doing a continuity test using a multimeter.
- Dry joints in the CRT board such as in the CRT socket pins, video pre amp and driver IC and even at the connector pins. In fact this problem contributed about 80% of Monitor color problems. Applying fresh solder would usually solve the color problem.
- A defective IC either in the Video Pre-amp or Video Driver IC.
- Faulty components in the CRT board. It could be a shorted driver transistor or even electrolytic capacitors that the ESR reading had shot up!
- A bad CRT socket. Sometimes decayed glue could cause the internal pins rusted and thus affecting the colors. Replacing only the CRT socket would definitely solve the problem.
- A weak or a defective picture tube (CRT tube). Yes, I do came across one of the electron gun (most probably the cathode materials had used up) in the tube faulty caused a missing color in the screen. There’s no way to repair this type of problem-the only way is to replace the CRT tube.
- In the newer type of Monitor, color setting is save in the EEPROM IC . Thus, if the EEprom data is corrupted, you would also get a missing color! The only way to repair it is to reprogram the IC or use a soft jig to tune it back the color setting.
Now, which one of the above is the easiest to start with first when comes to troubleshooting the color problem? I believe you would agree with me that the first, second and the third are the easiest compare to the rest. Normally I would hit the Monitor with my bare hands to see if there are any changes in color at the display (be careful not to hit too hard till the casing broken). If there is a change or flashes then I can say that the Monitor has dry joints. And if it stills the same no matter how many times I hit it, I will then starts check the VGA connector and the cable.
In the above Monitor, the problem was dry joints because when I softly hit it with my hand at the side of the Monitor, the blue color immediately appears. The aluminum shielding at the CRT board was opened and I could clearly see lots of dry joints especially in the video pre amplifier and the video driver IC. When you resolder please don’t just touch on the IC’s only, you need to resolder others area as well like the CRT socket pins. Doing this would prevent any color loss again in the future. A good job would prevent call back and to save you time and money and most of all your reputation!
After everything was done, you then need to gently knock at the CRT board again with the plastic handle of the screw driver to see if the color problem still exists. You may also knock on the main board just in case there is any dry joints there. One more thing, if you find that the Monitor is a bit dusty, you may use a vacuum cleaner and a brush to clean up the dirty area.
Whether you are repairing the g70fmb or any other brand of Monitors, if you come across any monitor color problem, you can always use the procedure above to find out the fault. If the VGA signal cable is okay and there were no dry joints in the Monitor, I guess the only way is to use voltage testing method and start checking components with your tester or meter.
Posted on Aug 05, 2008
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Posted on Jan 02, 2017
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