Sharp LC-70le550u back light flashes

[nwcs]

I have this sharp lc-70le550u that originally when turned on the back lights would lite up with no picture but had audio then would fade to black. Now the back light just flashes every few seconds and when they flash the 12v to the t-con from the power supply would drop to 0v then back up to 12v. If I disconnect the 12v to the t-con the led's stay lit. Sears had been out to the customers house and replaced the t-con and the main board with no fix. I am guessing that the power supply may be the problem. All other voltages seem to be good. Seems I have seen this problem before but can not find the fix. Does anyone have a thought?

[budwich]

Re: Sharp LC-70le550u back light flashes

disconnect one of the tcon cables (either side) and see what happens. You should get at least half a picture (depending on the side). Go from there once you get a stable screen hopefully.

[nwcs]

Re: Sharp LC-70le550u back light flashes

A little bit more info I do get 1.5v from pin 13 AC_Det and 5v from pin 15. No other voltages since it died.

[nwcs]

Re: Sharp LC-70le550u back light flashes

Somehow my last post did not get in. I did re seat the t-con cables to the panel and now the led's stay lit but still no picture. So I was checking voltages on the main board and when I got to pin 9 the set died. Now I only get pin 13 and pin 15 voltages on power supply. All else nothing. I am guessing I must have shorted two pins and killed the main board.

[budwich]

Re: Sharp LC-70le550u back light flashes

OK... but I don't want you to reseat the cable... I want to disconnect it and power it up. "things" should happen there after. IF nothing happens picture wise, then try the other cable on the other side of the tcon.... same test. report the results.

[nwcs]

Re: Sharp LC-70le550u back light flashes

Well as luck would have it I got in a lc-60le550u with different problem so I was able to do a little more trouble shooting with a know good t-con and main board. Back to original problem TV turns on backlight lights and no picture on screen. So unless power supply is the issue I think I have a bad panel. I had also replaced all of the cables with same problem.

[budwich]

Re: Sharp LC-70le550u back light flashes

But you need to do a test with the tcon cable disconnect (ONE). Input a signal and look for a picture. Then if nothing, do the other cable, same test. You should be getting something. Finally, if nothing, then with tcon all CONNECTED, disconnect the CORNER cable... this a small cable interconnecting the bottom edge boards to the side edge boards. What happens? If nothing, try the other corner cable on the other side.
bad panel??? doubt it..... but maybe ...SAVEABLE panel, probably... :-)

Of course, from your other post... "shorting" isn't good but I doubt you took out the main board, more likely your power board may have an issue... anyways. Again do the tests that I suggested and report the results.

[nwcs]

Re: Sharp LC-70le550u back light flashes

I will try all of that once I get it back up on the bench. Thanks for the help, I really appreciate it. I do not want to call it a bad panel unless it is.

[freakaftr8]

Re: Sharp LC-70le550u back light flashes

As far as I know I'm pretty confident that the 60 inch T CON will not work in the 70 inch panel even though they look identical the suffix at the end of the tcon is different as out t cons are suffixed ZH. I believe the 60 has a suffix of ze Anyhow I'm still thinking that you may have a bad side driver Make sure your T CON is putting out the acceptable proper voltages. First verify that you have 12 volts going into the tcon then if you look at previous posts you will find that you can check voltage is off each one of those small round coils on the tcon. This will verify that the T CON is putting out proper voltages to drive the panel

[nwcs]

Re: Sharp LC-70le550u back light flashes

deleted

[freakaftr8]

Re: Sharp LC-70le550u back light flashes

So no 5v and no flashing inverted v?

[nwcs]

Re: Sharp LC-70le550u back light flashes

Correct. I do have the 5v though. I thought I did not but it is there.

[budwich]

Re: Sharp LC-70le550u back light flashes

are we confused yet? :-) I am, first 70, then 60, then no voltage, then voltage... :-)

As suggested, try disconnecting one of the corner cables (of the panel), assuming you have voltages (confirm all the voltages on the printings of the power board), power up and see if you get a picture. If not, try the other corner cable.

Hopefully, the set will come up.

[freakaftr8]

Re: Sharp LC-70le550u back light flashes

Then your power supply is most likely okay

[nwcs]

Re: Sharp LC-70le550u back light flashes

The problem is I am doing way too many tv repairs 4 or 5 at a time and sometimes miss something. Anyway I did like you and freakaftr8 said and no picture. The TV was powering up with backlight at one time but now the only voltage I have is 5V. I even changed the battery in my meter to make sure. I removed one tcon cable at a time still no voltages or backlight of course.

[freakaftr8]

Re: Sharp LC-70le550u back light flashes

Okay let's start from the beginning. There are two white flat ribnon cables going from the tcon board to the panel. I want you to disconnect one side then power it up. Do you have a picture showing on 1/2 of the screen? If not then plug that one in and disconnect the other side and power up. Do you have a picture on that side of the screen?

[freakaftr8]

Re: Sharp LC-70le550u back light flashes

Ok just read that. You have no flashing inverted V representing an error code underneath the sharp symbol?

[nwcs]

Re: Sharp LC-70le550u back light flashes

did that and no there is no picture.

[nwcs]

Re: Sharp LC-70le550u back light flashes

no flashing v at all.

[budwich]

Re: Sharp LC-70le550u back light flashes

Does the "v" light up at all? You need to check ALL the voltages that are labeled on the power card.... especially those associated with the backlight powering. Do a diode check of the diodes and in and power from the transformers.