Noblex 32Ld858Ht TV there is no voltage at the source output
RSAG7.820.5268.pdf [1.50mb]
page 42
I still can't get standby v. The standby pin comes from the main card, and at the source it is not attached to any track. Only the pin is in the connector but it is not connected to anything .. I do not understand where the standby voltage comes from .. replace the missing fet mos (a 3n40c with an 8n60, there was another mosfet stk0765 which had symptoms of overheating on 2 pins (dys) for a 7n60, I read and had similar characteristics, and I still have no results.It is silent, I only have tension until the main filter of the hot earth and that tension reaches the drain of the 8n60
When the mosfets fly, the oscillator is almost certainly taken, you must change it. Measure all the components of the hot part, resistors, diodes, transistors, do not be guided by the appearance, measure them with multinetro. The source is repaired disconnected from the main.
If you measured the components with multimeter and observing the diagram, it is not flown, it has overheating marks between those 2 pins, but measuring it outside the plate (diode between dys) is fine, and also performing the shot on the gate measures normally .. I changed it in case that spark affected in something
Sorry for the questions, I am just beginning and I never touch something like that, the sources I reviewed earlier generated the standby and I could locate the 3 sources without problem to find the flaws .. but this I fail to understand at 100x 100 and I would like to achieve it
In fact, these sources are simpler even if the main voltage does not go to stby, it only uses the 12v generated by the source, the only thing that returns from the main is the pwm pulse train for the backlight and the pwr signal also for the backlight The first thing I try in these sources when I arrive are the schotky diodes of the secondary that are not short, then I check that the feedback is working correctly, once confirmed this there is no other than the problem in the hot part. Here the oscillator and mosfet are almost always compromised.
Thank you for clarifying these issues that I did not know, I had previously measured whether there was short or low resistance between output and gnd, I measured almost everywhere that I did not cut, in fact I tried to follow all the lines where I had serious doubts, one by one I tried to measure components smd resistors smd capacitors that are not short, (of course I measured each and every one of those that are mounted on the board as well as the state of the diodes) I suspect that integrated since it was the only component that I could not measure and neither I replaced, just check that there is no short between vcc and gnd
And I followed the connection tracks of this integrated, I saw that it is directly related to the optocoupler, which I had replaced, and try to follow the line of vcc, it is fed through resistors r812, r810, r806 (all 270k) placed in series with 2 resistors that apparently its nomenclature says that they are 0 ohms and are connected in parallel with each other. Measuring voltage with the board connected only to the mains I observe that voltage reaches r806 but taking a reading after r28 and 27 placed in parallel the voltage is 0.le ci ncp1251 is not powered