Sharp LC-90LE745U 3 slow and 1 fast Blink

[RDC55]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

I had thought about different strips and sizes that might cause a difference in Vf, but was hoping you would find an obvious issue like an open strip. The fact that they all appear the same my first thought is there is not an issue with the individual strips.

And just to ask what LED tester did you purchase? Most of the more inexpensive ones do not supply much current so on rare occasions they can give a false indication of the strips.

As for the number of LED's here is a link to an 80 inch backlit Sharp, and by my count there are 450 LED's (who would of thought that many?) so it is not a stretch to imagine the 90 inch having 500+ LED's.

http://www.tvpartscentral.com/sharp-...e632u-led-set/

The other question is why were the measured LED voltages so different when the forced on was done and the voltages measured? I can't find anything that says this TV has local area dimming, but that doesn't mean it can't individually control the LED strips to conserve energy. Perhaps others can weigh in on that? Perhaps we need to consider how to force the Power Supply backlight on to measure the strips to get a better evaluation of the Power Supply / LED strip. Budwich suggested something similar to this earlier but didn't provide details on how to enable the backlights - my guess is the STB pin but for now that's is just a guess so I don't want to direct the OP in that direction.

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

can't find a pic of this size with the screen removed LOL

to use the back light tester, i just put the positive on the LED1_A Pin then the black negative to the LED1_K pin. and when the LED light up, I noted the voltage on the tester. I'm assuming it's giving 197/198V on that one strip? then proceeded to LED2_A and LED2_K and so on up to LED16. all are showing 197/198V. if one strip is showing a different voltage then at least it should show that strip is defective. can we assume the backlight strips are ok? or maybe they are all bad LOL that's why it's showing all the same hahaha

oh dont touch the lead at the same time.....

[mmartell]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

That doesn't sound right even for a screen of that size does it ? Almost 1000 3v leds or even 500 at 6v ? I could be wrong of course...

Also some edge lit sets have leds at the top and sides and since they're different lengths the strings will have different forward voltages.

Would be good to see an internet pic of one of these with the screen removed.

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Got the backlight tester and tested all 16 strips.

They all light up and the voltage display is showing 197/198Volts.

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Yes, you will be checking the strips as you suggested above and not the individual LED's. However, when the LED tester is used on the strips the displayed voltage should be virtually identical for all the strips, which in essence verifies each LED is producing the correct Vf.

I have done some searching on replacement strips and haven't seen anything. It is nice to know what to expect and if you know the number of LED's per strip then it is easy to make an initial estimate.

Thank you. So if I understand it, when testing using the backlight tester to test the strips. They should all have the same/similar voltage. If a strip is showing more voltage (or less) then we can assume the strip is bad?

Hopefully we don't need to go that far.. removing that panel will be a pain LOL as just the TV itself is heavy and removing the panel at the same time trying to not to break LOL hahahah

[RDC55]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

To test the backlight, I'm assuming I will connect the backlight tester to the LED 1-A and LED 1-K which will be the + and - for the LED Strip? the power supply has 2 Connectors going to the LED strips. L1 connector is marked LED1-A, LED2-A, etc then L2 connector is marked LED1-K, LED2-k. once connected, I have to see if the backlight LED strip will light up right? through the small holes in the chassis? the test I'm going to do is to see if all strip will light up and not the individual LED lights right?

Yes, you will be checking the strips as you suggested above and not the individual LED's. However, when the LED tester is used on the strips the displayed voltage should be virtually identical for all the strips, which in essence verifies each LED is producing the correct Vf.

I have done some searching on replacement strips and haven't seen anything. It is nice to know what to expect and if you know the number of LED's per strip then it is easy to make an initial estimate.

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

To test the backlight, I'm assuming I will connect the backlight tester to the LED 1-A and LED 1-K which will be the + and - for the LED Strip? the power supply has 2 Connectors going to the LED strips. L1 connector is marked LED1-A, LED2-A, etc then L2 connector is marked LED1-K, LED2-k. once connected, I have to see if the backlight LED strip will light up right? through the small holes in the chassis? the test I'm going to do is to see if all strip will light up and not the individual LED lights right?

When we initially installed the main board, the heartbeat blinks once during the power and the tv tried to turn on the shutdown after with the 1-1 blinks. Tried few times then it went to the 1-1 immediately. So the count might have reach 5. But can’t reset it as can’t go to the service menu I think it's storing the Code on the main board as the power supply does not power on/click anymore when it's doing the 1-1. the Main board might not be sending the PN-ON and PN-POW signal to the Power Supply to turn it on.

For the heartbeat, if the TV is on the blinking 1-1 state, the main board does not blink anymore. But if we force boot or try to go to Service menu. Then it’s flashes.

Ordered a back light tester and will test and update.

again, thank you very much for all the assistance and knowledge

[RDC55]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

You can purchase a backlight tester fairly cheap, in the area of $20 USA.

No need to remove the screen to test the backlights. You can do it from the connectors that mate with the power supply.

And yes, removing that panel is probably the last thing you want to do, so a thorough diagnosis needs to be done first.

I was curious also, is the heartbeat indicator flashing every 2 seconds or so with the new board?

It is also an interesting thought about where the backlight fail count is stored. Say for example if it was stored on the Main board and the board you received has exceeded the 4 count and needs to be reset, or is it stored on the Power Supply and reported to the Main?

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Do you have an LED tester? It appears the TV is a full array backlit version with nothing about local dimming that I could find. When looking at the LED voltages that you posted a couple are suspicious, which I think warrants checking each individual string.

And just to add it was stated earlier that STB was standby, but you can find other info posted about Sharp TV's indicating that is the actual BL_ON command.

How old is the TV?

The TV is around 7-8 years old.

I dont have a back light tester, i can check and see if they are not that expensive that I can purchase. To test the back light strip, do we need to remove the panel/screen or can we do it just on the wire connector?

coz I've seen videos of repairing the strip but that involved removing the screen panel itself and that thing is delicate hahahd and removing a 90 inches screen is not going to be fun hahahah

I'm just checking the power supply board to see if there's any shorts if not, then we'll decide if we still going to have it repaired or for parts.

[RDC55]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Do you have an LED tester? It appears the TV is a full array backlit version with nothing about local dimming that I could find. When looking at the LED voltages that you posted a couple are suspicious, which I think warrants checking each individual string.

And just to add it was stated earlier that STB was standby, but you can find other info posted about Sharp TV's indicating that is the actual BL_ON command.

How old is the TV?

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Hello, it sounds like you need to go into service mode and clear the backlight error count. Doing the force turn on does not clear anything it is just for testing for troubleshooting. Once the error count is clear you should not get the 1-1 blink (unless there is still a led issue) any longer.

Yeah unfortunately pressing the input and volume down. The tv flash and the backlight flicker and then back to 1-1 blinks

[nicholas1110]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Hello, it sounds like you need to go into service mode and clear the backlight error count. Doing the force turn on does not clear anything it is just for testing for troubleshooting. Once the error count is clear you should not get the 1-1 blink (unless there is still a led issue) any longer.

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Deleted, duplicate post

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Here are the pics of the board and connection. can't take the whole back as it's standing in the hallway and can't back out more hahaha :P

so it seems if we force it to boot up (Channel down and Volume UP), the TV works, can power off/on, change input, access menu etc. as long as we dont unplug it, it will work.

if we unplug it, then replug, it goes to the 1 slow 1 fast blink. the only way we can make it work is to do the force boot up when plugging in.

Also anyone has a schematic of the power supply? I'm measuring 0 Ohms on D7511 and D7508 (not sure if there's a coil parallel to it LOL haven't done the soldering removal yet).

for the L7502 (C1580) is that a transformer? I'm assuming it should be 0 ohms since it's a transformer? I compared the measurement on the bottom 2 C1543 and i'm getting 0 Ohms if measured on both ends of the terminal..

only if we have some schematics on this power supply so it's would be a bit easier to follow LOL

let me know

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Update:

I did the jumper again PIN 14 (PN-ON) and PIN 15 (BU5) without Jumping Pin 16 (PNL-POW). here are the voltages.
Connector to Main board
1-2 0V
5-8 13.05V
13 - 3.04V
14 - 4V
15 5.04V
rest are 0V

L1 Connector:
1 - 16 113V
L2 Connector:
1-26 0V

No Backlight.

when I plugged the Main board and do the force start - Power Channel Down and Volume up.
L1 Connector:
1 - 16 276V
L2 Connector:
1 to 4 106v
7 113V
8 106V
9 104V
13 124V
14 92V
17 106V
19 106V
20 107V
23 107V
24 107V
25 107V
26 107V

when I access the menu, L2 goes to around 92Volts

Connector to Main board
1-2 11.94v
5-8 13.05v
13 3.22v
14. 3v
15 5.04v
16 3.26v
17 0
18 3.27
19. 0.90v
20 3.27V
21 .12V
22 3.26V
24 3.24V

backlight are turning on.

Somehow the regular boot up is detecting there's a failure on the backlight and not going through the whole process. and based on the service manual, there's an option to reset the LAMP count but I cannot access the service adjustment menu

any other suggestion?
Will post some pictures later..... it's on my phone lol

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Got the board today. Just got it installed, I saw the main board led blink 1 once. The screen flashed and got a new error code . 1 fast and 1 slow.

I will try to open the whole back and get the voltage measurement as suggested. This TV has lots of screws hahaha

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

This is interesting concerning the LED on the Main board - from the update manual attached above.

"The Heartbeat indicator will flash about every 2 seconds when the Main PWB is working normally. This is an indication that data communications is operational.
The Heartbeat indicator will also flash 1 time when initial AC power is applied"

Thank you, I saw that one too regarding the heartbeat. that's why i'm wondering LOL

[c00lman]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Thanks. I’m planning to open it next week and follow the test voltage measurements.

[budwich]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

Ah ok. when I plugged in. The ps-on has 3v. Just the pnl-pow is not getting 3v from the main board. So it might not be in standby. If I remember. The voltage on the big caps jumps from 130v to 300++

We'll see next week when the replacement board comes in. If it's still doing the same thing then we'll see hahaha. Can't find any power supply board replacement anymore.

Thank you

the whole point of the test that I suggested is to remove the main board from the system / control so that basically you have the set powering up and creating proper voltages. IF that happens, you can start checking other things by tracing (without powering up) where some of those voltages go from the power board to the main board. Again, lots of this type of problem can be caused by a main board failure but also a panel issue. There are other tests in terms of "cable disconnecting: tcon to panel", etc. That will help determine where a problem might lie.

[RDC55]

Re: Sharp LC-90LE745U 3 slow and 1 fast Blink

This is interesting concerning the LED on the Main board - from the update manual attached above.

"The Heartbeat indicator will flash about every 2 seconds when the Main PWB is working normally. This is an indication that data communications is operational.
The Heartbeat indicator will also flash 1 time when initial AC power is applied"