After commissioning found that there are three fault phenomenon at the same time: uZnservice manual download site
Line 1. The range is narrow and pincushion distortion: 2. The screen from time to time automatic popup menu "lock". Can't adjust the simulation parameters: 3. The image is too large. A grey one. uZnservice manual download site
 uZnservice manual download site
When the "lock" menu don't appear. Adjusting the simulation parameters, found that in addition to the line, both pincushion correction data change, the grating constant, the rest of the project to adjust the image has the change, but adjust brightness, contrast to the minimum value into the screen is still bright. uZnservice manual download site
 uZnservice manual download site
 uZnservice manual download site
Considering the screen don't appears regularly lock "menu", can't line, pincushion distortion amplitude regulation failure caused by it? When machine to work properly if the menu button for 15 seconds. Lock will appear "menu". Therefore suspect the fault in the key circuit, row line after fault still pull the panel buttons, illustrates the fault in the main circuit. uZnservice manual download site
 uZnservice manual download site
The machine from keying ribbon cable to the CPU pins only two components: stabilivolt C211 ZD211, capacitor, tests were normal. Inadvertently found the CPU + 5 V power supply voltage of 6.5 V above, measuring voltage regulator to block IC601 (S78DL05L) output voltage is 6.5 V. Doubt its performance is bad, try common three-terminal voltage regulator block 7805 after replacement, measuring its normal output voltage of 4.9 V, and the word "lock" menu will no longer appear. But then adjust the amplitude, grating pincushion distortion calibration still don't move! uZnservice manual download site
 uZnservice manual download site
In desperation, considering the image brightness is too high. Brightness is line circuit failure, pillow school adjustment is not normal? Brightness by the analysis of circuit, the machine is controlled by the CPU through the bus visual circuitry change a picture tube cathode voltage to control the screen brightness level. Rather than through kinescope G1 voltage to control, so the G1 voltage to a fixed value. It is by the line. T502 (9) foot after D504, C509 rectifier filter - 160 - v voltage. Then through R516, R515 partial pressure. Measured C509 on both ends of the voltage of 160 v.

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