DEAD SET.
Troubleshoot should startup with AC mains power cord itself. Just check the two conductors of the power cord for continuity. Can check it continuity by using a multimeter set to Ohms range.
In these sets, AC mains power is passed through a fuse [galss cartidge type]; can be located at the main power reulator section. The fuse is marked [F801 - AC 250V 4 AMPS]. Check this fuse first. If it is found opened, never insert an other fuse with same rating. There will he some reason for the blow out of this fuse.
Set the multimeter to measure Ohms range. Measure the reistance across capacitor [C801 - 0.47MFD AC250V]. The meter should measure a very high resistace. If it show very low resistance, make sure that some short circuit is there at the AC input circuit.
Check the load reisistor [Negative] (R802 - 3.3Ohms 7W). If this reisistor found open, check the four mains rectifier diodes [D837_D838_D839 & D840]. If any one among them has junction short, the mains fuse and R802 might get damaged. It is best to replace all these four diodes. Four of them are [LT 2A05G]. You can use any rectifier diodes, such as 1N4007 or so.
Desolder out [L802] and check the resistance across [C805 - 100MFD 400V _ MAIN DC FILTER]. If resistance acorss this capacitor is found very low, must check all the four rectifer diodes and four disc ceramic capacitors connected in parellel with these four diodes for leak. Still the multimeter reads low resistance across [C805], check the freewheeling capacitors (C842 - 1000Pf 1KV & C807 - 2200Pf 1.5Kv ). These two capaciors are of special types, and replacement must be done with capcitors have similar characteristics. It might be leaky, and will be the fault for the blown up fuse.
If all said above components are OK, and there is no short circuit measured with multimenter, after desolder out [L802], make sure that the main switching MOSFET [ Q801 - SK2671] is faulty. check the resistance between the source and drain leads of this MOSFET. If the MOSFET is good, there should be very high resistance in one direction. If it shows very low reistance in both directions, the MOSFET is damaged.
If the set do not switch ON, even if all the above components are good, and Fuse is Ok, check the two resistors connected in seris to the Gate of the swiching MOSFET and AC input line. These two reistors in series, supplies the start voltage. If any one among them is open, there will be no start voltage to MOSFET. The start supply voltage to main switching control IC [I802 - DPM001TIA], pon number (5) too get through these reistors.
There are five output voltages from the secondary side of the SMPS transformer. 133VDC, 45VDC, 16VDC, 12VDC & 5V regulated DC].
When work with power supply section of this set, tempeorarly desolder out [Q802 - KSA 1013Y]. Replace it only after all work has been done.
On the secondary side of the SMPS transormer, not much fault has been detected. The only fault found so far is the failure of protection zener diode [D835 - R2M].
Check all the solder terminals of components, which will heat up during working. If any dry solder is detected, desolder them by applying a little more fresh solder. It is a good practice to resolder all the suspected solder terminls.
If anybody want the service manual to this set, contact me.
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