Changhong color TV C2151 grating expansion and contraction fault repair example - Appliances

SMD aluminum electrolytic capacitor

Tantalum capacitor

A3 movement color TV grating expansion and contraction common reasons to repair a Changhong C2151 color TV, the fault is the full scale of the grating when starting, and soon a large expansion and contraction, measuring ten B1 voltage (130V) between 130V ~ 90V ~ 130V change, The pulse width control tube V512 (2SC3807) b-pole voltage varies between -3.6V and -3.0V, and this voltage is -1.8V when it is normal. After investigation, the capacity of the feedback winding rectification filter capacitor C515 (0.015μF/63V) has been reduced to 4700pF. Later, he repaired two Huangshan H2588C/R color TVs. One of the power indicators was on. The output of the 10B (130V) terminal was measured. The pulse width control tube V312 (2SC3807) b voltage was 0.6V, and the feedback winding rectification was removed. Filter capacitor.
C317 (0.015μF/63V) is measured with a capacitance meter and has no capacity. Another dimming small grating that shrinks after power-on, measures V312 b voltage between -2.6V and -3V, +B voltage varies from 70V to 100V, and removes C317 to measure its capacity is only 4460pF. It can be seen that when the A3 movement color TV has the above-mentioned fault or occasionally fails to start the power, it is possible to measure the b-pole voltage of the switching power supply pulse width control tube first, so as to quickly determine the fault location. To prevent this from happening again, it is recommended to replace this 0.015μF/63V polyester capacitor with a 0.015μF/160V metal film capacitor. At the same time, it should be noted that it is not possible to turn on the machine for a long time when overhauling the faulty machine with large shrinkage of the grating, so as to avoid the unstable under-low +B voltage causing the over-current of the pipe to break down.