First, determine the field circuit may be bad . Observe IC451 (LA7837) was Weld Pins majority state , after careful welding test machine , the same fault . Shake the board found that the level of bright lines instantly expand and there is no relationship between the rocking board , but randomly appear , indicating that the internal circuitry associated with the field of a component is bad or performance deterioration .jaAservice manual download site

IC451 be completed including all fields , including the field oscillation circuit function , simply enter the field of external sync signal , it takes two kinds of +12 V and +24 V supply voltage . Measured IC4511 pin +12 V and +24 V 8 feet were normal and stable, try changing IC451 invalid. Monitoring IC451 associated pin voltage changes, found two feet in the horizontal bright line is about 1.5V, while the bright lines instantly jump into shape when open around 4.5V. IC4512 feet for vertical sync signal input terminal , visible failure is due to vertical sync signal station lost cause . See related circuit drawings and vertical sync signals IC60131 output pin all the way through the Q1104 and other inverted , screen positioning signal for the CPU to make ; another path , such as the magnitude of the Q403 for IC451 for field conversion trigger signal. Since visible on the left side of the green character is compressed when the level of a bright line , so you can think IC60131 foot has a normal signal output , the fault should be between IC4512 IC60131 foot to foot . When no abnormal road test Q403 , R405, R406 resistance is normal, the normal state of repair switch S601 , S601 taking into account the relatively high failure rate , removal of S601, but the fault persists, calm analysis IC4512 foot work and the level of fault unpredictable , indicating a fault with the power supply components should be linked components. So after replacing the R406 (22kΩ, 1/8W), the image back to normal.jaAservice manual download site