Open observation, components and solder joints on printed circuit boards did not see unusual, measuring line output tube Q501c of resistance within the normal range. Try on the power switch, after waiting for the start-up observed kinescope filament light, don't stay there grating was put out, immediately issued a "ji ji" sound, switch the power source if cut off the power immediately after boot, appear filament can't light up and turned on "ji ji" sound, shutdown boot filament can light up again a few seconds, then fault again. 5mrservice manual download site
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Failure, measured Q501e voltage is normal, b voltage for ov, preliminary judgment line output circuit is normal, the fault may be a protection circuit action, causing IC601 (AN5601) no conduct caused by excitation signal output. AN5601 (42) foot line to start the 8.6 V power supply side, (41) foot line for excitation signal output terminal, AN5601 did not see the X-ray protection, X-ray protection is by controlling (42) foot line to start the power supply, R529, R561 and I) 502 X-ray sampling circuit (see chart). D523, C582 and D522, D520 filament over-voltage/under-voltage sampling circuit; R411, Q451 form field power supply current detection circuit; R420, R415, R426 form field output voltage, current sampling circuit. Normal work, line change T501 (5) to (3) on the winding line flyback pulse; Except for the filament power supply in another path D523, C582 rectifier filter after about 24 V dc voltage, after R541 R542 points, will be about 9.3 V voltage is added to the D522, D520 cathode, D520, D522 partial cut-off, Q503, Q504 also ended, the normal work of the machine. When the voltage increase (or decrease) + B or other causes of the filament winding line flyback pulse significantly higher or lower, after rectification, filtering, partial pressure circuit voltage is higher (or lower), when the voltage rise D522 against wizard sense, Q504 due to B and e are extremely partial saturation conduction, Q503b, e is partial saturation conduction. Because Q503 self-locking circuit, Q504 into silicon controlled type, therefore, no matter which one leading expert will make them have saturated conductivity, cause IC601 (42) JiaoHang start power flow, line oscillation circuit and losing electricity cannot be maintained. Line output stage because there was no excitation signal to stop work, so as to achieve the purpose of protection. Limited to space, other protective circuit principle.

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