1) don't light, a fried 5A F2 ~ F3 in insurance
Two 5a of insurance is a series consisting of 10 dual MOSFET in power push-pull circuit, which F2 series on the right Q1 Q2, Q5 to Q7 dual MOSFET, F3 Series in the left Q15 ~ Q16, Q19 to Q20 and q22 two MOSFICT.
Generally speaking, which insurance fuse, and the series of double MOSFET breakdown short-circuit related. After the replacement of the short-circuit of the double MOSFET can solve the problem.
2) without a 5A 5A insurance, insurance intact intact
The XgMOSF'ET is not connected with the phenomenon of short circuit, and the fault should focus on the backlight control IC (DMB8110D) and its peripheral circuits..
First, check the power supply of DMB8110[1.. If normal. The voltage output of the VREF pin of the 5V pin of its reference voltage should be checked, and the oscillation signal of the oscillating circuit is especially the oscillating signal of the triangular wave, and the 17 voltage of DMB8110D is normal, and the output of the signal is especially exciting..
In general, the excitation circuit are not light a lamp and dual MOSFET and a transformer, wherein the power push-pull output circuit and six IR2184S without direct contact. Because lo a push-pull output and six excitation circuit, backlight board. At the same time can not be damaged, as long as there is a group of normal and DMB81IOD have excitation pulse output of the lamp can be bright again protection.
3) boot can light the lamp, but the moment extinguished
This is clearly belonging to the backlight protection fault. There are two cases of backlight protection, one is over-voltage protection 0VP. One is overload protection 0LP. In the actual maintenance process, the overload protection of the 0LP function.
At normal working time, the 11 pin voltage of DMB8110D is around 60mV.
Jump into 5V when protected. Artificially canceled protection can be Protin protection points or U5 (L, M339) 14 or 9 pin with a wire to the ground, the lamp is no longer extinguished but the brightness will be reduced.
For the maintenance of this fault, the first person to cancel the protection. Let it work for more than lO minutes. Touch the temperature of the transformer by hand.. If a transformer becomes hot, the transformer turns a short circuit. After the replacement of the fault can be excluded: if the temperature rise of the 20 transformers are normal. The power output circuit and the protection circuit are the key to check the circuit fault..
Which is the protection of the road: D36, IM6, D59 six diode anode voltage, normal 30mV, if the road is high. The road has the problem, the transistor Q24, Q25, Q29, Q30, Q32, Q33 base voltage, normal time O-3V, if the low fault is still in front of the sampling circuit. If normal, the fault in the transistor and its bias; diode D45, D63...... Cathode voltage. At normal time, the transformer sampling and its bias should be checked when the bias is larger for O.56V..