Grating suddenly became bright, tube beam current increases suddenly. After the beam current is too large, over-current protection circuit starts, the main power shut down, "squeak" screams the machine. Tjxservice manual download site
Cause of beam current is too large has: (1) the apparent breakdown, at the end of the tube to tube cathode potential; Breakdown, (2) three inspect the pipes Q303 reduce apparent at the end of the tube emitter voltage and collector potential decreased, and (3) the two apparent Q302 open, make Q302 collector potential drop, 0303 base and emitter voltage drop, lower the apparent at the end of the pipe collector potential; (4) anode and kinescope filament, cathode and grid pole, lower the cathode potential; (5) the luminance channel damage of other components, such as breakdown of C307 D301 strike chuan, etc., will cause the loss of tube cathode voltage, beam current increase. Tjxservice manual download site
(1) the beam current is too large to produce protection action. Can put board will consider first when maintenance M801 from tube inserted, and then electricity, tube beam current, nature is no protections. Tjxservice manual download site
(2) and electricity at the end of the test tube collector voltage, only 10 V (typically 140 ~ 150 V), measuring M800Y input terminal voltage of 0 V, three depending on the tube at the end of the emitter is only 4.6 V. Brightness channel is out of order, to see at the end of the pipe emitter collector voltage is reduced, so that the Cambodian current increases, the tube itself is good. Tjxservice manual download site
Three (3) the test as the pipes Q303 emitter voltage of 0 V, the base voltage 5.6 V, that as of 0303, emitter to ground fault. Tjxservice manual download site
(4) check Q303 emitter circuit component, found ZD301 breakdown, causing Q303 emitter of short circuit. After replacement ZD301, 11 v voltage regulator tube, troubleshooting. Tjxservice manual download site
Breakdown, caused by the common cause failure are: C303 Q307 breakdown, Q302 open, C304 open circuit, etc.Tjxservice manual download site