Hisense 40K360 I changed the oscillator 4071 x 4071B and it only gives
Friend seekude thanks for answering, maybe your source is similar because I do not have the transistor you mention I have the v946 with 1P license plate, I also did not understand where to place the 12 v source, could you continue helping me ?, if you have the diagram you could help me facilitate ?, friend dni20 I will check what you say you will not have the diagram ?, I will continue commenting on your help
https://www.electronica-pt.com/esquema/lcd/rsag7.820.4737-38072/ What is done from the external source is done to see if the feedback stage is cold. Since upon reaching the established tension you must saturate the opto. The transistor that I mention is the one that saturates when a high level arrives from on in the main, this to simulate the source as if the TV was on.
friend seekude, note that the transistor mentioned V916 is not present on the board, even though I bridge where CE should go ?, also where I connect the external 12V source and if something has to be disconnected, could you indicate if it is not too much trouble ?
As is, it appears in the diagram but not on the plate, which the source is at its tension in the same way in standby as in operation, so you can place a regulating source.
Note, also replace optocoupler, see if the tl431 is correctly placed and that you are of the same voltage reference. I leave the points to be measured, I do this procedure with all the sources that I repair, it never fails:
https://drive.google.com/file/d/1zzddQFSiL-yZOGuWWuOOtA6O7WrW0MtU
friend to do the test, I mark about 5.2 K ohms to increase the low voltage to 800 ohms, so you tell me the feed back is fine right?
something else to check?
It is stable, but let me tell you that the voltages in the primary section are not stable: VD622 ranges from 12 to 6 Volts, in VD804 from 95 V to 65 V, I did the test replacing some zeners and remains the same and in the output in the secondary As I mentioned at the beginning it ranges between 6.3 and 9.2 Volts, which could already check or change the dream but it must stay and more with your valuable help
What happens is that the oscillator ic first at the start takes tension from ac with a half wave rectifier (vd804-r810) pin 8 hv, once it started to oscillate it is fed from a winding of the vcc chopper. What is happening is that it enters a loop, starts, cuts and so on. See that the v946 is healthy.
According to the diagram is an MBT2222A, change to test with a normal mounting PN2222A and remain the same
They measure well, how to know if the problem is in the primary and not in the secondary
The secondary is easy to discard. As I indicated before measuring in the optocoupler, and making sure if there are no diodes like those of the chopper output in short, you can also place an external source and check consumption, which should be infamous when not having a load. I think that this source is feeling bad current, that is, tell me if you repaired any of these R849 r844 and r847. You can remove the protection to see if it comes there, but you run the risk of carrying the mosfet and the oscillator. The other diagram indicates that it carries an ncp1271a
no, do not change the resistors that you mention because they measure their value well, indeed the oscillator originally had the ncp1271A, I got the ncp 1271 B, according to the data sheet it supports more frequency than I put it, but seeing that it was exactly the same fault I returned the original ncp1271A
Okay. Well, what we could try is to see if it comes from an incorrect sensing, the only problem is that if there is a safe overconsumption the mosfet will fly and you can wear the oscillator too, as security, well whenever you repair sources it is convenient place a lamp (incandescent bulb or if it does not get halogen) in series with the mains plug, we would say about 40w incandescent or 65w halogen, this in case there is a short or high consumption will act as a limiter without burning, the lamp if there is a short will turn on brightly, if not ...
... when the source is empty, it will only turn on a second at the beginning when the capacitors are empty. Well if you want to proceed to disconnect the current sensing that the oscillator has, what you should do is lift R845, but as I said before you can get to burn mosfet, but very attentive to the lamp, if it is on, disconnect quickly. Comment
friend seekude thanks for your help the measurements you mentioned are pin 1 adj almost 500mV, pin 3 CS 3mV and pin 6 VDC ranges from 6 to 11.5 V
friend seekude, I have changed your suggestions and remain the same, I put a focus of 12 volts where there should be 12V and the voltage stabilizes at 8.3 V, I made measurements in the primary in VZ801 and I have 13.4 V, in VD831 and there are 12V, the VD828 does not exist and rare thing in VD 816 according to the diagram there must be 60 V and it measures me 110 V
In the test with variable source when the voltage increased and half the optocoupler pins to which voltage this decreased the resistance? Before I said that after 12v, but just in case we will try again. If you have a variable source that goes from <3v to 13v, you could measure while the voltage is increasing slowly, as I mentioned before, it should mark on the Mhoms scale and when it reaches the regulation point it should fall to <1kohm, if it falls before it is bad the regulation part.
that you think, I already have 12V, several surface resistors that involved the reference voltage of the TL431 were devalued. But now just turn on a front LED below where the Hisense brand is, but the stnby LED does not turn on, now the problem has to be in the main will you have the main diagram? is the RSAG7.820.5028 / ROH
Friend I want to thank you for your great help, the problem has already been solved, the front ed was precisely the stnby, check some things and I'm here, I will value your great help and close this thread. I will see how, greetings and thank you very much
Friend as I value you and commented that the fault had been resolved, but I think it remains open, if you want to publish any suggestions such as changing the regulator or whatever to give you as the solution.
regards