This simple circuit provided here is for those who are restoring old tube-type TV sets. I don't recommend that you tackle TV restoration unless you have prior experience with  television restoration or repair. Picture become weak or dim usually happen after the monitor have been used for many years. Again it depends on the quality of the picture tube or cathode ray tube (CRT). Some grade A CRT can last for many years, but for the lower grade one it can only last for couples of year. Don’t be surprise that I do come across picture tube that had gone dim in less than a year! If you switch on your monitor for 24 hours without turning it off, then expect the tube to become dim fast.

Besides dim (weak emission) , CRT may also develop many problems such as open filament, short between cathode and heater, G1 and G2 short, poor gamma performance, stripped cathode and focus and G2 short. The cathode ray determines the brightness and sharpness of a picture tube. Its electrons are emitted from the cathode surface into the cathode ray tube’s vacuum. The electrons then strike the screen in the form of a ray and cause it to shine. Weak or used up cathodes produce few electrons and emit weak electron rays. This causes the picture to become dark and fuzzy. Sometimes the cathode emission ceased due to a layer of contamination coating covers the cathode surface. This contamination prevents the electrons from leaving the cathode’s surface thus you get a dim picture. All CRT restorers, including the most expensive, are based on the same principle applying discharges between RGB cathodes and  G1 inside the tube to remove from the cathodes microscopical particles deposed on them during the CRT lifetime. Those particles diminish the electron emission, and by removing them the tube may be restored.

   The homemade device pictured here is good enough to do this work and gives a good service to the TV and monitor repairer in all cases when the tube is not totally unrecoverable (all vacuum electron emitters have a limit). I have tested it with many types of tubes and found it useful except in Samsung and some EMC tubes, in  monitors. I  guess Samsung tubes are  the worst. I have never tested it  with Trinitron  tubes, but I do not see any  reason for not trying it,  only that I have  not yet met any exhausted  tube of these. The circuit  is very simple, and  you can make it  recovering old materials.