Little Help with Sharp LC-80LE642U

[Robottom]

Re: Little Help with Sharp LC-80LE642U

I will post a follow up as soon as the new power board gets here just to let anyone who is interested know if that was the cause or not.

HOWEVER, I really want to say THANK YOU to all the good folks on this forum. Thank you for the help and advice, as Mr. Schwarzenegger would say ... I'll be back.

[budm]

Re: Little Help with Sharp LC-80LE642U

You have 16 strings of LEDs, put the Black probe of the meter on the chassis, red probe go to the LED1- turn on the TV and see what the DC Voltage goes up to and record that number then turn the TV off, move the red probe to LED2- and turn the TV on and record the Voltage, do the same for the other 14 strings of the LEDs and post the result of the reading.

[Robottom]

Re: Little Help with Sharp LC-80LE642U

New board arrived this afternoon, same exact ... start with "Input" & "Vol-" held down, get one short flash of the LEDs and then nothing until the power board clicks then it goes back to one short and one long blink. Dang it!! Was hoping to at least have the LEDs stay on long enough to make sure there weren't any out. I'm still pretty sure they were all on when I saw them flash but I think now I have to assume that it could be a short and the current is going through out of bounds. Is it possible to test for a short across the LED strip with a multimeter? I have a diode setting but when I tried diode and ohms the other day I got OL regardless, swapped leads both directions through the strips.

Also, with respect to testing all of the outputs from the board to the LED strips, I tested several skipping some in between. I figured there are four inverters, so I hit enough places to make sure that I had a pretty good chance of testing all four. I didn't want to keep powering the system up and down because that's been taboo in my experience with other electronic systems.

Anyway, NOT the power board, so I think I'm back to trying to figure out how to get enough voltage and current to power the LED strips individually. Or find a way to test them without power. If anyone has a better idea than stringing a bunch of batteries together I'd love to hear it.

Thanks,
Tom

[dskall]

Re: Little Help with Sharp LC-80LE642U

They sell led testers : https://www.ebay.com/sch/i.html?_fro...tester&_sop=12

[budm]

Re: Little Help with Sharp LC-80LE642U

You have 16 LED- return (you can see 16 MOSFETs on the heatsinks for the LED Cathode returns) for 16 strings of LEDs, we are looking for the return side of the circuit not the supply side, so even with LED tester you still need to test ALL 16 LED strings.

[Robottom]

Re: Little Help with Sharp LC-80LE642U

They sell led testers : https://www.ebay.com/sch/i.html?_fro...tester&_sop=12

Thank you, checking to see if Fry's or another local electronics store has one in stock. If not will order from eBay.

[Robottom]

Re: Little Help with Sharp LC-80LE642U

You have 16 LED- return (you can see 16 MOSFETs on the heatsinks for the LED Cathode returns) for 16 strings of LEDs, we are looking for the return side of the circuit not the supply side, so even with LED tester you still need to test ALL 16 LED strings.

I will test all 16 strings with the tester as soon as I get one.

I was worried about too many cycles power up / down on the boards and didn't want to plug and unplug that many times.

When you say test and looking for the return side, could you be more specific. What does test mean and what would I be looking for?

Thank you!!

[Robottom]

Re: Little Help with Sharp LC-80LE642U

Reading back through this wanted to say that it's really hard to get reliable readings because the power board shuts down the output to the LEDs so quickly.

I've ordered an LED tester from eBay, no one within 50 miles of me had one on the shelf.

[budm]

Re: Little Help with Sharp LC-80LE642U

I will test all 16 strings with the tester as soon as I get one.

I was worried about too many cycles power up / down on the boards and didn't want to plug and unplug that many times.

When you say test and looking for the return side, could you be more specific. What does test mean and what would I be looking for?

Thank you!!

The LED are driven by constant current, the Anode of the LED strings are fed by V+ from Voltage boost converter circuits, the Cathode return of each string is connected to the Drain of the PWM control power MOSFET, the Source pin of the MOSFET is connected to the current sensing resistor, another end of the resistor is connected to the ground return. The Vdrops on the sensing resistor is used as feedback to the LED driver IC to maintain constant current through the LED string by PWM drive the Gate of the MOSFET. The LED driver circuits will go into protection shutdown if it detect open LED circuit, shorted LEDs in the LED strings. So when you look at the LED- you are looking to see if one of the string has open circuit or not, LED tester will tell you if you have open circuit too. The LED tester will be able to tell you if one of the LED string has shorted LED/LEDs or not by comparing the Vf reading of the LED strings since string with shorted LED will still light up but will have lower Vf so you have to look at the Voltage readings on the tester to tell you what you are seeing.
See PDF for example, your TV uses external MOSFETs instead of the internal as shown in the example IC but still the same basic topology.

[Robottom]

Re: Little Help with Sharp LC-80LE642U

The LED are driven by constant current, the Anode of the LED strings are fed by V+ from Voltage boost converter circuits, the Cathode return of each string is connected to the Drain of the PWM control power MOSFET, the Source pin of the MOSFET is connected to the current sensing resistor, another end of the resistor is connected to the ground return. The Vdrops on the sensing resistor is used as feedback to the LED driver IC to maintain constant current through the LED string by PWM drive the Gate of the MOSFET. The LED driver circuits will go into protection shutdown if it detect open LED circuit, shorted LEDs in the LED strings. So when you look at the LED- you are looking to see if one of the string has open circuit or not, LED tester will tell you if you have open circuit too. The LED tester will be able to tell you if one of the LED string has shorted LED/LEDs or not by comparing the Vf reading of the LED strings since string with shorted LED will still light up but will have lower Vf so you have to look at the Voltage readings on the tester to tell you what you are seeing.
See PDF for example, your TV uses external MOSFETs instead of the internal as shown in the example IC but still the same basic topology.

Got it, thank you, will post results sometime next week. The tester is ordered but apparently not shipped yet due to the holiday.

Happy 4th !!!!!

Thanks,
Tom

[Robottom]

Re: Little Help with Sharp LC-80LE642U

Readings with L1 and L2 cables disconnected, using 0-300V backlight tester on the pins of the L1 and L2 male connectors.

L1............LED Strip......Voltage..........L2 (Actual).....(As Marked)

1---------------1---------175v---------------1...................1
2---------------2---------175v---------------2...................2
3---------------3---------175v---------------3...................3
4---------------4---------175v---------------4...................4
5---------------5---------175v---------------7...................7
6---------------6---------175v---------------8...................8
7---------------7---------174v---------------9...................9
8---------------8---------175v---------------13.................13
9---------------9---------175v---------------17........*.......14
10-------------10--------175v---------------19........*.......17
11-------------11--------175v---------------20........*.......19
12-------------12--------174v---------------23........*.......20
13-------------13--------175v---------------24........*.......23
14-------------14--------175v---------------25........*.......24
15-------------15--------175v---------------26........*.......25

Note that the L1 connector wiring matched what was marked on the board and matched which LED strip actually lit up. The L2 connector wiring did NOT match what was marked on the board. The L1 and L2 Actual pin pairs are the ones that lit up the LED strips from top to bottom, counting them as 1 through 15.

Also, all LEDs lit up equally, none were any dimmer or brighter than any other. Of course that based on my naked eyes which aren't very well calibrated any more, but .....

I was not setup to take current measurements, can do that tomorrow, but am not expecting any surprises there either.

The only thing I can think of is that maybe the wiring harness may be shorting to ground or something like that. I tried using an ohm meter earlier to test pins on L1 and L2 to ground but will try again in the morning just to be sure.

Any other suggestions, ideas, tests that could help isolate the problem would be much appreciated.

Thanks and best regards,
Tom

[Robottom]

Re: Little Help with Sharp LC-80LE642U

Performed three different checks this morning, no other indication than normal. Running out of ideas.

Connected backlight tester black lead to chassis ground.
Then put red lead on every connected pin on L1 to see if anything lit up. Nada.
Tested continuity from every connected pin on L1 to chassis ground. Nada.
Tested continuity from every connected pin on L2 to chassis ground. Nada.

Just as a follow up, here's pictures of the connectors and actual pinout verses what's marked on the board.
I can't believe this would have anything to do with my issue though as it's been like this since new.

Note that the board is marked L2 - 14 as if LED 9- were connected there but pin 14 on the L2 connector is empty.
LED 9- is actually connected to L2 - 17 and the remaining wires are all pushed back to the next pin as marked, with LED 15- landing on pin 26 as there is no LED 16.

[budm]

Re: Little Help with Sharp LC-80LE642U

So far the Total Vf readings of the the strips do not show abnormal Vf readings.
https://www.badcaps.net/forum/attach...3&d=1498509608
Can we get the DCV reading of the PD connector when TV is OFF and when power switch is activated?
Please make sure to put down the pin number and follow by the pin name and follow by the reading when TV is OFF and when TV is ON?

[Robottom]

Re: Little Help with Sharp LC-80LE642U

So far the Total Vf readings of the the strips do not show abnormal Vf readings.
https://www.badcaps.net/forum/attach...3&d=1498509608
Can we get the DCV reading of the PD connector when TV is OFF and when power switch is activated?
Please make sure to put down the pin number and follow by the pin name and follow by the reading when TV is OFF and when TV is ON?

These readings were taken with the LCD panel disconnected.
The only way I could get "Power On" was to repeatedly keep resetting.
Meaning that I would unplug, hold "Input" & "Vol -" and plug back in.
The LEDs would all flash on then go out and power would only stay on only for a few seconds.
Then the power board would click and the Icon light would start flashing again.

Also, not below, I might have missed pin 16 PNL_POW on the on tests.
I have it recorded both time as 0v but think I might have missed it for power on due to the short amount of time I had to take readings.

PIN....NAME..........Power Off.......Power On
1----PNL_12V----------0v----------12v
2----PNL_12V----------0v----------12v
3----GRND-------------0v----------0v
4----GRND-------------0v----------0v
5----UR13.2V----------0v----------13.3v
6----No Name---------0v----------0v
7----UR13.2V----------0v----------13.3v
8----No Name---------0v----------0v
9----GRND-------------0v----------0v
10---No Name---------0v----------0v
11---GRND-------------0v----------0v
12---No Name---------0v----------0v
13---AC_DET-----------0v----------3.3v
14---PS_ON------------0v----------3.3v
15---BU5V-------------5v----------5v
16---PNL_POW--------0v----------0v ***
17---VSYNC(GSP)-----0v----------0v
18---SCL---------------0v----------0v
19---No Name---------0v----------0v
20---SDA--------------0v----------0v
21---OFL--------------0v----------2.3v
22---ERROR-----------0v----------3.3v
23---No Name--------0v----------0v
24---STB--------------0v----------3.3v

Please let me know if this helps and what if any other tests I might perform.
If the Error indication is coming from the Main board, do you think I should replace the main board or test it somehow.

Thank you!
Tom

[Robottom]

Re: Little Help with Sharp LC-80LE642U

Thought I'd try something on my own while waiting for a some feedback on signals posted previously.

I unpinned PD - 22, the ERROR signal and tried resetting, (plugging in with "Input" & "Vol -" held down). I was hoping that the lack of the ERROR signal would allow the power board to light the backlight LEDs and keep them lit. Unfortunately it didn't change anything so I have to assume that the power board is not seeing some signals in whatever order it wants or it's detecting some error on it's own that doesn't come from the main board.

The ERROR signal did go high 3.3V immediately and stayed there until the system shut down again but there was no other change in the sequence.

Reset start produces a short bright flash of all backlight LEDs, icon light stays lit solid for 20 - 30 seconds until the power board clicks and shuts down, then the icon light goes back to flashing one short, one long.

[Robottom]

Re: Little Help with Sharp LC-80LE642U

OK, well here's my last attempt asking for help. The wife is loosing it. I'm going to have to literally pull the plug and buy a new TV if this doesn't work.

After all of the above, I broke down and bought a refurbished Main Board, no joy.
Figured what the heck I'm this far into it, bought a used but good TCon board, still no joy.
Last ditch effort I repined L2 to match what the power board says and still no joy.
(note from above the mismatch between board as marked and L2 as pinned)

So, to summarize:
I tested all of the LEDs.
They all seemed to be good with readings 174 - 175 VDC.
I also tested both sides of the LED strips to ground with an ohm meter.

Then I replaced each board in turn, power, main, and finally tcon .... still no joy.

The symptoms never changed.
Regular start gives one short and one long blink from the icon.
Reset start short bright flash out of the LEDs, then nothing until the power board clicks and the icon goes back to flashing one short one long.

Any last thoughts before I pitch this this thing into the ocean?
Anybody want to buy a bunch of used parts?

Thanks for the help I did get, but can't keep beating this horse.

[martino]

Re: Little Help with Sharp LC-80LE642U

I'm missing one test in all this,unless I read over it.
The 70" models and also 60" suffer from chips on the panel burning up.
To test for that:
Remove left ribbon cable from t-con to panel,reset tv and try it.
Reconnect left ribbon cable,remove right ribbon cable,reset tv and try tv.
If in one of those two tests you get halve a screen that works then the fix is easy.

[budwich]

Re: Little Help with Sharp LC-80LE642U

hopefully, he will get something from this. I mentioned this earlier but didn't really follow up with the "limited" response. There are also "corner cable tests".
Anyways, its tough to see an 80" on the street. :-(

[Robottom]

Re: Little Help with Sharp LC-80LE642U

Disconnected left ribbon cable from the tcon, reset start.
Got one bright flash of the backlight LEDs and a few seconds later the power board shut down and the icon light returned to blinking. (Same as previous)

Reconnected left ribbon cable disconnected right ribbon cable, reset start .... same as previous.
Disconnected both ribbon cables, reset start ..... same as previous.

Disconnected cable between main and tcon reset start got one bright flash of the backlight LEDs but the power board stayed on and the icon light didn't start blinking.

What are corner cable tests?
I'll keep trying until the wife shoots me but have a feeling that won't be much longer.

Thanks again!

[Robottom]

Re: Little Help with Sharp LC-80LE642U

I'm missing one test in all this,unless I read over it.
The 70" models and also 60" suffer from chips on the panel burning up.
To test for that:
Remove left ribbon cable from t-con to panel,reset tv and try it.
Reconnect left ribbon cable,remove right ribbon cable,reset tv and try tv.
If in one of those two tests you get halve a screen that works then the fix is easy.

This all started after a power outage, is it possible that both side chips blew out at the same time?

Where are the chips located?