Sharp Aquos 70" LED LC-70LE632U does not power on

[Teletubbie]

I have a 4-year old TV that was working fine all along until last week it just turned off while watching a show. The power light on the front panel does not come on when you try to turn on using the remote or the front power switch.

I have read all the related old threads on this forum and I need some guidance in troubleshooting.

I have attached the service manual, pictures of the back panel, power board, T-con board and main board.

I have a multimeter and a soldering iron if needed for repairs.

Thanks in advance.

[budwich]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

disconnect one of the two tcon cables and see if it powers up. If not, try the other. Still if not, disconnect both. After that still nothing, you need to start checking voltages on the power board.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Disconnected the cable from T-con to the main board and it did not power up.
There are two more ribbon cables that run from T-con to the bottom of the TV panel. Not sure how to disconnect them; cannot find any tabs to press. I do not want to try something and damage that cable. Any suggestion how to disconnect the T-con ribbon cables?

Edit: Found out here how to disconnect those ribbon cables.

Disconnected both the cables one at a time and then disconnected both together and it did not power up the TV for any of the cases.

Let me know what voltages do you want me to check on the power board.
Thanks!

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Can anyone help me troubleshoot my TV?

[awyatt2]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

you don't have standby, look at the power board and see where the stby comes from, have you checked fuses?

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

I checked the fuse on the power board. How do I check the standby?

[budwich]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

:-(

you can try to reset the tv... unplug the set. then on the side panel, depress volume up and channel down at the same time, hold, and then plug the tv back in.... do you get any response. (note release, the buttons once something happens).

Further, get a meter and follow the power in from the cord to the power board and check a few point s there after to see if it is actually getting anything. Go from there... there should be voltage labels on the board to help you "trace things".

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Tried the reset procedure and there is no response from the TV.

Should I power up the TV when I check the voltage?

Here is a higher resolution image of the power board from ShopJimmy.

[budwich]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

just ensure the tv is plugged into a working socket. Hope you know how to use a multimeter to measure things. Be careful as you are going to "visit" areas that can kill you if you do things wrong with your fingers. Measure the voltage coming into the set. It should be line voltage. It is likely going to some form of switch power supply / rectifiers. check some points around the area to see what you find... there should be labels at connectors, at some various points if you are lucky. You can work either forward from the incoming ac plug or backwards from the connectors leaving the power board.

There are service manuals on this site (search / look around), although typically the power supply is not included but some info can be gleamed from the other board's info.

People (good guys) will respond to you IF you post good info (hint -> pictures.... read the sticky on how to use the forum / posting).

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Power Board Testing

I tested the voltage at the input point and it checked out okay at 123V. The fuse also tested okay.

Did a visual inspection of the capacitors and there is no obvious bulging or leaks.

I set the multimeter to Diode mode and all the diodes on the board tested around .45 V except the one marked in red in the attachment which showed 0.

I am assuming the components marked with FB on the board are ferrite bead and they appear like a diodes with a solid black color without any color band. Do I need to test them?

[budwich]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

sorry but I can't seem to see what you reference the "red marked diode".... do you have a component number. If the diode (s) are all similar in response and one is not, its a good chance that you may have found your issue. However, "in-circuit" testing isn't always "concise". Potentially, you might have to "lift" one lead of component from the board to isolate it a bit and go from there.

[budwich]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

as for the ferrite beads... they are basically jumpers, so unless they have significant issues (broken / burnt / cracked solder joint), I doubt they are the problem.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

sorry but I can't seem to see what you reference the "red marked diode".... do you have a component number. If the diode (s) are all similar in response and one is not, its a good chance that you may have found your issue. However, "in-circuit" testing isn't always "concise". Potentially, you might have to "lift" one lead of component from the board to isolate it a bit and go from there.

I do not have a parts list for this board. I see there are two numbers printed on that red-marked diode. "10" on the first row and "22" on the second row. Do you think I should desolder this diode to get an accurate reading?

[budwich]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

the device reference number from the board is d7951. Anyways, once you desolder one side, you will likely see what the actual component number is. Further, if you look on the circuit side of the board, you should be able to potentially see what it is connected to. From the picture, it is near a transformer so it is likely taking an output from one of the legs of the T and rectifying it. Potentially, once you see the output of the transformer and accessible "test access points", you should be able to check for voltages coming out of the transformer in some form just to further confirm your suspicions about the diode... maybe.... as opposed to possibly the transformer being shorted which might have thrown of the "in-circuit" diode test.

[freakaftr8]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

On the PD connector do you get any output dc voltages at all? Looking for a pin with 5v or 3.3v. also what is the.voltage you measure across capacitors C7800 a thru c?

[freakaftr8]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Also agreed on the diode. It could be in parallel with the transformer giving an off reading. The only way to test that diode is desolder one side and read it's measurement.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

On the PD connector do you get any output dc voltages at all? Looking for a pin with 5v or 3.3v. also what is the.voltage you measure across capacitors C7800 a thru c?

Connected the TV power plug and checked the PD connector. No voltage present on any test points.

Disconnected the power and checked the C7800s. All the capacitors A thru C measured 39.3 V DC.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

the device reference number from the board is d7951. Anyways, once you desolder one side, you will likely see what the actual component number is. Further, if you look on the circuit side of the board, you should be able to potentially see what it is connected to. From the picture, it is near a transformer so it is likely taking an output from one of the legs of the T and rectifying it. Potentially, once you see the output of the transformer and accessible "test access points", you should be able to check for voltages coming out of the transformer in some form just to further confirm your suspicions about the diode... maybe.... as opposed to possibly the transformer being shorted which might have thrown of the "in-circuit" diode test.

After I turn the board over, how do I test the transformer? I would like to first check the transformer voltages and make sure it is not shorted before I desolder the diode. Thanks.

[freakaftr8]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

You need to check the main PFC capacitors with the power plugged in. Black lead to negative on capacitor and positive with red lead. You should have about 170 volts DC across each of those capacitors

[freakaftr8]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

After I turn the board over, how do I test the transformer? I would like to first check the transformer voltages and make sure it is not shorted before I desolder the diode. Thanks.

I seriously doubt anything's wrong with the transformer. The reason i mentioned desoldering and pulling up one side of the diode is to properly test it out of circuit. The transformer will give a Non conclusive reading With the diode in circuit due to the fact that the transformer is completing a circuit on both sides of the diode