Analysis of Common Faults of Samsung 40 - inch DMB Program BacklightWDsservice manual download site
1) do not light, fried 5A insurance F2 ~ F3 oneWDsservice manual download site
The following are the same as the "WDsservice manual download site
Two 5A insulators are connected in series with 10 dual MOSFETs on the power push-pull circuit, where F2 is connected in series on the right Q1-Q2 and Q5 to Q7 pairs of MOSFETs, F3 in series on the left Q15 to Q16, Q19 to Q20 and Q22 MOSFICT on.WDsservice manual download site
In general, which fuse fuses, it must be related to its double-stranded short-circuit breakdown. Replace the short circuit after the dual MOSFET can solve the problem.WDsservice manual download site
2) do not light, 5A insurance intact 5A insurance intactWDsservice manual download site
The following are the same as the "WDsservice manual download site
Indicating that there is no short circuit between XgMOSF'ET in series, and the fault should focus on the backlight control IC (DMB8110D) and its peripheral circuits.WDsservice manual download site
First check the power supply of the DMB8110 [1]. If the power supply is normal. Should check its reference voltage VREF feet have 5V voltage output, oscillation circuit with special triangular wave oscillation signal, DMB8110D 17 voltage is normal, there is especially the excitation signal output.WDsservice manual download site
In general, no lighting phenomenon with dual MOSFET and transformer composed of power push-pull output circuit and six IR2184S excitation circuit is not directly linked. Because the backlight board has lO push-pull output and 6 excitation circuit, can not be damaged at the same time, as long as there is a group of normal, DMB81IOD excitation pulse output, then the lamp can be lit and then protected.WDsservice manual download site
3) Turn on the lamp, but turn off instantlyWDsservice manual download site
The following are the same as the "WDsservice manual download site
This is obviously a backlight protection fault. Back of the backlight described in front of the situation there are two, one is overvoltage protection 0VP. One is overload protection 0LP. In the actual maintenance process, are overload protection 0LP work.WDsservice manual download site
Normal operation when the DMB8110D 11 pin voltage is low level 60mV or so.WDsservice manual download site
Protection transition to 5V. Artificial cancellation of the Protin protection point or U5 (L, M339) 14 or 9 feet with a short circuit to the ground, then the lamp is no longer off but the brightness will be reduced.WDsservice manual download site
For the maintenance of this failure, the first man to cancel the protection. Let it work lO minutes or more. Touch the temperature of the transformer one by one. If a transformer becomes hot, it is the transformer inter-turn short circuit. Replace the fault can be excluded: If the 20 transformer temperature rise are normal. It should focus on checking the power output circuit and protection circuit for open circuit failure.WDsservice manual download site
Distinguish between which way protection: measured D36, IM6, D59 six diode anode voltage, normal when the 30mV, if measured which way high. Q32, Q30, Q32, Q33 base voltage, normal when the O-3V, if the low is still fault in front of the sampling circuit. If normal, then the fault in the transistor and its bias; measured diode D45, D63 and other cathode voltage. Normal O.56V, the deviation should be checked when the transformer sampling and its bias.WDsservice manual download site