Sir Hemant Choudhary . . . . .
That systems dual polarity, DUAL LEVEL power supply shifts up from the low level, which you currently have, to the full supply level after the filters take on their initial charge.
This is being accomplished by RY100 and its Q1016 driver, at the top of the power supply schematic via command from Q1015.
However . . . . it seems that you have a circuit fault, so the supply never steps up to that full secondary value.
This units problem should be what I was sort of expecting to be the fault on your previous unit.
Consult page 117 of the schematic . . . . .
Then you locate your top STK433-130 power amp module, used for the SURROUND Right and Left channels.
The lower STK433-330 is responsible for the MAIN R and L channels PLUS the extra burden of the center channel.
Inside of the power modules each channel has a pair of output transistors stacked between the Plus 50 and Minus 50 supplies.
If all is well within the module, the voltages balance out and there is a static cancelling out and almost zero volts DC normally being at their outputs, which fed to their speakers.*****
Then, as audio is applied to a channel, a coincidental voltage swing to the waveform is replicated at the output of the module . . . all in accordance as to how high you have the volume advanced..
These modules are sampled for the current consumed by them, the peak voltage swing that they produce ( in case you have no speakers connected, and you then run the volume to max, since you heard nothing ?)
And finally, the the DC voltage at the output to the speaker, of each amp, as I previously related to in *****.
Let's start by having you look at the right edge of the schematic and work from top to bottom in locating the separate sensing transistors Q1007---Q1008---Q1012---Q1011 and Q1006.
Those transistors bases are sampling each channel and the outputs off all of the sampling transistors are collectively fed into Q1013 base, so that fi8nal transistor can respond if any fault is found on any the 5 tracked stages.
There are also being two additional clusters of fault finding circuitry, but lets start with the just mentioned one first.
Connect DC voltage metering with the negative lead to anywhere on the heavy black ground buss.
Positive meter lead, will be going in a testing sequence, to the separate bases of Q1007---Q1008---Q1012---Q1011 and Q1006.
You turn on the set and notice the max voltage reading experienced , just for that instant, and log down.
Then you power down and move on to the next transistor.
Give back the voltages and we will see where we need to go next.
73's de Edd
....