Image grow to be weak or dim typically come about soon after the monitor have been employed for a lot of yrs. Once more it is dependent on the top quality of the picture tube or cathode ray tube (CRT). Some quality A CRT can final for a lot of yrs, but for the decreased quality one it can only final for partners of calendar year. Really do not be shock that I do come across picture tube that had long gone dim in much less than a calendar year! If you switch on your monitor for 24 hrs devoid of turning it off, then be expecting the tube to grow to be dim quickly. Apart from dim (weak emission) , CRT might also develop a lot of difficulties these kinds of as open filament, limited between cathode and heater, G1 and G2 limited, weak gamma overall performance, stripped cathode and focus and G2 limited. In this post, I’m likely to contact on the weak emission difficulty only and exhibit you a feasible way to brighten up the picture tube.
The cathode ray decides the brightness and sharpness of a picture tube. Its electrons are emitted from the cathode area into the cathode ray tube’s vacuum. The electrons then strike the monitor in the type of a ray and trigger it to glow. Weak or employed up cathodes create couple electrons and emit weak electron rays. This brings about the picture to grow to be darkish and fuzzy. In some cases the cathode emission ceased owing to a layer of contamination coating addresses the cathode area. This contamination stops the electrons from leaving the cathode’s area hence you get a dim picture.
In purchase to identify whether is the tube that trigger the dim or from lousy elements, one can usually use a CRT tester/meter to check it. Some phone it CRT rejuvenator, CRT restorer and some others named it as CRT regenerator. These testers are built to examination and check CRT and fix it if the picture tubes have difficulties. I personally owned two CRT testers- the BMR 2005 Muter regenerator and a much less element one I acquired from Thailand. With the help of CRT tester, I can know if a picture tube is doing work or not. If you do not have one, do not be concerned because by examining the voltage at the CRT socket pin outs, you will have some thoughts if the CRT is very good or lousy.
From my professional, I recognized that the more mature tube can be brightening up with the help of CRT tester but not for tubes that was built in the calendar year 1994 and previously mentioned. I suspect the getter (built of barium) within the tube have been employed up. The capabilities of getter within the tube are to take in fuel that was launch when the cathodes are warmth up. If the getter fails to take in the fuel, then there is no place to restore a picture tube. I have brightened up a lot of picture tubes with the help of CRT tester and some appears like a new tube. But someway soon after one or two days the picture tube get dim yet again because the getter are not able to take in the fuel and the fuel will travels back again to the cathode area and flip it into carbonate. Electron emission will stop yet again. I even have tried out some household built CRT restorer downloaded from the internet and the consequence is continue to the same-the picture tube will dim back again soon after partners of days.
Following accomplished some study and experiment, I found that the best way to brighten up the tube is to enhance the heater voltage. Standard heater or filament voltage is about 6.3 volt and if you enhance the voltage to about 8 to 9 volts, this indicates the cathode will create more electrons and hence the monitor will grow to be brighter. Bare in mind that do not implement any voltage that is greater than 9 volts to the heater otherwise the internal filament will melt away out and damaged. As soon as it is open then there will be no way to rescue it.
If the picture tube is heading to rubbish dump then there is no harm to check out to restore it. About how very long it will final, I are not able to warranty it. Some will final even more than two yrs and some only partners of months. Not long ago there was a badge of Compaq and Hp 15” monitor that have the symptom of blur show with bright picture. No issue how tricky you check out to alter the focus adjustment at the back again of flyback transformer, the picture continue to look a bit blurs. Applying the strategies previously mentioned I had saved a lot of picture tube (I do not need to have to exchange a second hand one to buyer).
It is a very simple modification and this only applies to the 14 and 15” monitor picture tube only. Initially you need to have to uncover which secondary output that have output from 12 to 15 volts. As soon as you have track down it, then solder a wire at the cathode pin of the diode and join it to the enter pin of 7808 (output 8Volts) voltage regulator. Remember to do not tap from the B+ voltage which is typically 45 volts and previously mentioned and this might eliminate the 7808 IC because this IC can only stand up to voltage up to 38 volts highest. The current drawn from the 14 and 15” picture tube is much less than the 17” tube and if you use this way to brighten up the 17” tube, the ability source might go into shutdown method and at times will even lead to ability blink.
I do know some technicians like to use the method of turning couple rounds of wire at the flyback ferrite main to restore the brightness. This method can work in Television but not in Observe. Laptop screens runs in a lot of resolution and the greater the resolution the greater the B+ voltage and hence producing the output voltage at the wire elevated. This will lead to a sudden brightness and might shutdown the monitor. Even if it didn’t shutdown, the buyer might get annoyed with the Observe brightness (raster) anytime the buyer transform the monitor resolution.
Now solder the pin 2 of 7808 IC to chilly floor and the output of 7808 IC pin 3 to the CRT heater place as shown in the picture. Bear in mind to reduce off the 6.3 volt source line from the ability source because you do not need to have it any longer. What you need to have is the 8 Volt source to the filament in the picture tube. You can also link a reduced ohm protection resistor in collection to the heater place. Just in situation if any limited circuit happens the resistor will open circuit. Make guaranteed you attach the 7808 IC to the heatsink, preferable the heatsink at the flyback transformer.
This method only work for tube that is a bit blur and not way too dim picture. If a picture is incredibly dim even if you raise the heater voltage to 12 volt, you continue to would not see a bright picture. As talked about previously mentioned there is no harm seeking to modify it and who is aware of the tube can be brought to life and provide the buyer for a lot of yrs. Hope you take pleasure in the post.