Sometimes can work normally low luminance color TV Hitachi CHF 321 or the signal is weak; but when the high brightness or when a strong signal is received, immediately "fault repair method -" -Service Manual Download|Circuit Download|Download Drawings|schematic download|route map download|free download user manual

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Sometimes can work normally low luminance color TV Hitachi CHF 321 or the signal is weak; but when the high brightness or when a strong signal is received, immediately "fault repair method -"

Time：2014-07-22 09:40:56 Source：Network Author：Unknown Clicks：1318

According to the user, the machine had repaired many times to the person, ever changing three pipe, two ignition coil, a power thick film circuit STR - 6020, but every time is always not how long it is broken again after repair. naeservice manual download site
Look from the fault phenomena like is "ABC" circuit, but the M51393 o14. GIF (65 bytes), o15. GIF (66 bytes) feet peripheral components carefully check them one by one, it found that these components are good. The two feet of potential explains basic normal, the fault is related to brightness and signal strength, but the root cause of failure is not in the circuit. naeservice manual download site
naeservice manual download site
naeservice manual download site
Measured at the end of the three level depending on the pipes of the collector tube (that is, the cathode) only about 120 v voltage, slightly lower than normal, but depending on the power supply circuit is normal, namely D377 negative terminal voltage is greater than 180 v. naeservice manual download site
Then check over current protection circuit. When using a multimeter in the zener 2 d751 negative terminal monitoring over-current voltage change situation, found that the voltage to 3.5 ~ 3.7 V, appears "stall", shows that the zener "too sensitive". The pipe down to measure (leakage) found its reverse resistance smaller. Replace a new tube boot after test, the results into a point at which the voltage to 3.7 ~ 4 v has not "shut down", but when the over-current voltage rise to about 5 v, still "shut down" phenomenon will happen. naeservice manual download site
At this time, should make key check for the power circuit. Directly connect with multimeter voltage in power supply output voltage monitoring changes. Finally found the power supply voltage will automatically jump from 120 v to 120 v or above, more than once to the high voltage power supply part have a slight "squeak" cries, cries like a "line", "stall" very quickly at the same time, this action shows that automatic over-voltage protection circuit.

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