Sharp aquos lc-40le820e power on problem

[j120975]

Good afternoon to all of you. First of all sorrybfor my bad English. I have a sharp aquos tv ,and i m dealing this problem. If i leave the power cord disconnected,then it starts normally for one minute approximately. After that the tv restarts and only the touch panel lights working for about 10 seconds and only 1-2 seconds lights up the led panel. After that loop again. No signal lights in center. I think probably is a power supply problem . I can see 5 v ,13.3v in 4 pins . I m a mobile technician and i can follow your instructions if you yave some suggestions. Thank you in advance.

[dick_barton]

Re: Sharp aquos lc-40le820e power on problem

What is the power supply board number. Is it DPS-126CP ????
If it is then you need to measure the voltages on connector PD pins 9, 10 and 12

[j120975]

Re: Sharp aquos lc-40le820e power on problem

Pin 9 1,20v at the beginning and 3,0v after 2 seconds .pin10 3,05v ,pin12 0,12v. Board is dps-126cp-1 a

[dick_barton]

Re: Sharp aquos lc-40le820e power on problem

Pin 12 = 0.12V
The Panel Power (PNL-POW) signal derived from the mainboard is not present (missing). PNL-POW switches on Q7909 to provide the 12V for the Panel,
You should be able to press Menu on the remote control and use a bright light shone on the LCD screen at various angles to see the Menu displayed.

[nomoresonys]

Re: Sharp aquos lc-40le820e power on problem

Maybe check your voltage regulators also, video example there: https://www.youtube.com/watch?v=ocqnqmBxiqY

[j120975]

Re: Sharp aquos lc-40le820e power on problem

this morning update.After many hours with power cord disconnected ,i plugged this morning and everything works fine for 1 minute.All voltages present.13.3v,5.0v,high voltage capacitors 308volts on stand by and 400+when on.But after one minute ,disaster again.Now high voltage capacitors is 316 volts on stand by ,5,0v present and 13v only for 3 seconds when i press the on button on the remote control.And only 2 quick flashes on central pyramid and 1 longer period led off

[nomoresonys]

Re: Sharp aquos lc-40le820e power on problem

Check all the diodes on the powerboard, meter in diode mode, should get a reading in one direction then reverse meter probes should read 1 or OL if any read strange de-solder one leg and test out of circuit, keep in mind that other components on the circuit can make it read strange while still in circuit. So if any read off in circuit tell us which one/s, then we can check if there's a reason why it might read off.

[j120975]

Re: Sharp aquos lc-40le820e power on problem

These diode's are shorted when in circuit.(d7717,d7703) Out of circuit is ok. So ,what component should i check; The strange thing,is that. If i power on the tv today ,after a few days off,is working perfectly for a minute. After that lights on-off.

[nomoresonys]

Re: Sharp aquos lc-40le820e power on problem

Some testing there, does seem like a mainboard issue, maybe check the voltage regulators on the mainboard as he is in the video: https://www.youtube.com/watch?v=ocqnqmBxiqY

[j120975]

Re: Sharp aquos lc-40le820e power on problem

So , update. I check the mainboard today ,and i found that. These three capacitors are shorted to ground when the are on circuit. I desolder them ,and they are ok. The short-circuit is coming fro this ic3604. This is the M2303ADN. Maybe a suggestion of equivalent ic;

[nomoresonys]

Re: Sharp aquos lc-40le820e power on problem

See if that's it: https://cdn.badcaps-static.com/pdfs/...4969373d5b.pdf