Image fuzzy by poor video frequency amplifier, focusing tube voltage change and display their own bad cause, brightness is not enough by tube power supply voltage, such as accelerating voltage, control the bias, anode voltage and other abnormal and kinescope consenescence, cathode emission ability is not enough to cause. 2jtservice manual download site
(1) receiving image signal, will light up, adjustable focus potentiometer, observation scanning and image details, found that raise or lower the focus voltage when the image is less clear, focus voltage is normal. 2jtservice manual download site
(2) is set to accelerate teaching voltage adjustment potentiometer R371 found high voltage adjustable brightness increased slightly, but the image is more fuzzy, and immediately have a flyback lines appear, which showed that the accelerating voltage is normal. 2jtservice manual download site
(3) the observation line did not change, when accelerating voltage of high voltage circuit basic normal, measuring 900 v output rectifier is also normal, high pressure circuit can be ruled out. 2jtservice manual download site
(4) according to the above analysis, basically can determine is tube ageing. For the purpose of reliable. The string on the R558, ammeter to measure 110 mu A maximum beam current. Everything is back to normal after replacing kinescope.2jtservice manual download site