Emerson LF501EM4F turn on then off.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

Well I pulled it apart and guess what I found. Yep one strip of L.E.D's are not working. So I tested it with one of the other plugs. It acts up sometimes it comes on sometimes it doesn't and I see one led out on the strip but after like 10 secs it starts to flicker and it comes on.
I looked on ebay there is a set but they say Samsung these in mine are LG. but they look identical.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

Yep I think I'm going to do that. Open her up and see for sure

[SLK001]

Re: Emerson LF501EM4F turn on then off.

Zero volts on PROTECT3 indicates a failure mode for the LEDs. Are you sure all the backlight strings are on, or just one of the three, or two of the three? Pin 7 of the LED controllers are all tied together, so if one fails, PROTECT3 will be pulled to ground, indicating a failure mode.

I'm afraid that you're going to have to crack her open and examine those LEDs.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

And they stay on as long as the AC is applied to the board?
Also check the DCV at the PROTECT 3 jumper to see if it has 2~3VDC on that jumper.
BTW, it the PROTECT 3 signal is OK, then we will need to look at PROTECT 1 signal.

OK I just had the backlight on for 10 minutes no problem. Stayed on the whole time. I checked protect 3 in like 4 different spots but I'm not getting any voltage. The spot for protect1 there is no jumper there it only shows this sign. - - - - - - - - - - -

[budm]

Re: Emerson LF501EM4F turn on then off.

And they stay on as long as the AC is applied to the board?
Also check the DCV at the PROTECT 3 jumper to see if it has 2~3VDC on that jumper.
BTW, it the PROTECT 3 signal is OK, then we will need to look at PROTECT 1 signal.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

OK, I look at the diagram, it does not have any pull-up resistor for the BL-ADJUST, so you need to add another 1K between the BL-ADJ and the 3.3v stby.

OK jumped bl-adj/J137 and backlight is on...

[budm]

Re: Emerson LF501EM4F turn on then off.

OK, I look at the diagram, it does not have any pull-up resistor for the BL-ADJUST, so you need to add another 1K between the BL-ADJ and the 3.3v stby.

[budm]

Re: Emerson LF501EM4F turn on then off.

OK , you need to look for the BACKLIGHT-ADJUST jumper (BL-ADJ J137), it should have around 2~3VDC on it, if not we will need to use another resistor.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

So when you put the resistor between the 3.3v and the P-OB-H2, do get the DCV at the P-ON 21V? if you do then the power supply is being forced ON OK. You did use 1K resistor, right? 2V should be more than enough to turn on all 3 switched Transistors on that power supply board.
Looking at the diagrams:
PROTECT 3 is the error signal generated by the backlights circuit to tell the main board the condition of the backlights circuit.

PROTECT 1 is the error signal if the power supply lost the AMP+13V or p-on+21V.
Normal condition the DCV at PROTECT 1 and 3 should be around 2~3VDC, <1V = bad.

OK just picked up 1k 1/2 watt resistors. Tested it all over again.
Jumped 3.3v to j106/bl-sw with 1k resistor getting 3.2v there.
Jumped 3.3v to ps-on_h2 with 1k resistor getting 2.4v on ps-on_h2.
I'm getting 21v at p-on+21v and I'm getting 12v at amp+13v.
So PS is on.
I do have the backlights plugged in and they ARE NOT lighting up..

[SLK001]

Re: Emerson LF501EM4F turn on then off.

Do you have the rest of the service manual or the download link? Thanks!
I download this one and it looks the same.

I downloaded from here

There is only the power supply that I found, but I had to search by the board number. You might be able to find more data with a search by board number of interested components.

[budm]

Re: Emerson LF501EM4F turn on then off.

Here's a good set of schematics for this board.

https://www.badcaps.net/forum/attach...1&d=1463019635

Do you have the rest of the service manual or the download link? Thanks!
I download this one and it looks the same.

[budm]

Re: Emerson LF501EM4F turn on then off.

It might be my testing. Imy having a hard time finding a 1k resistor. From 3.3v to p-on_h2. I'm getting at the end of the resistor 3.3v but once I touch it to p-on_h2 it drops down to 2.0v. Which might be to low.

So when you put the resistor between the 3.3v and the P-OB-H2, do get the DCV at the P-ON 21V? if you do then the power supply is being forced ON OK. You did use 1K resistor, right? 2V should be more than enough to turn on all 3 switched Transistors on that power supply board.
Looking at the diagrams:
PROTECT 3 is the error signal generated by the backlights circuit to tell the main board the condition of the backlights circuit.
PROTECT 1 is the error signal if the power supply lost the AMP+13V or p-on+21V.
Normal condition the DCV at PROTECT 1 and 3 should be around 2~3VDC, <1V = bad.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

Here's a good set of schematics for this board.

https://www.badcaps.net/forum/attach...1&d=1463019635

Ty I'm having a hard time reading it. Little blurry

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

It might be my testing. Imy having a hard time finding a 1k resistor. From 3.3v to p-on_h2. I'm getting at the end of the resistor 3.3v but once I touch it to p-on_h2 it drops down to 2.0v. Which might be to low.

[SLK001]

Re: Emerson LF501EM4F turn on then off.

Here's a good set of schematics for this board.

https://www.badcaps.net/forum/attach...1&d=1463019635

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

No cable between the power supply board and the main board, LED connector in place, do the resistor jumper for the PS-ON (P-ON-H2) as before, then another resistor between the jumper J106/ BL-SW and the 3.3V to force the backlight on, see if the backlights will stay on.
Pictures provided by shopjimmy.
http://www.shopjimmy.com/emerson-a3a...pply-unit.htm#
Emerson A3AU0MPW-001 Power Supply for LF501EM4 / LF501EM4F

OK I jumped 3.3v to j106. But backlight didn't come on.

[budm]

Re: Emerson LF501EM4F turn on then off.

No cable between the power supply board and the main board, LED connector in place, do the resistor jumper for the PS-ON (P-ON-H2) as before, then another resistor between the jumper J106/ BL-SW and the 3.3V to force the backlight on, see if the backlights will stay on.
Pictures provided by shopjimmy.
http://www.shopjimmy.com/emerson-a3a...pply-unit.htm#
Emerson A3AU0MPW-001 Power Supply for LF501EM4 / LF501EM4F

[SLK001]

Re: Emerson LF501EM4F turn on then off.

Yea I understand that but it does it even went I have the back lights disconnected.
I have only power to the ps board and the ribbon from ps to the main and it still shuts down.
And if I jump 3.3v to ps-on the ps board stays on all with correct volts.
It just seems like a bad main board. But it is from shopjimmy.

You should get an LED FAIL signal with the backlights disconnected, too (open circuit detected).

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

The description sounds like you have bad LEDs in your backlight. There appears to be more than one string of LED power. When you turn the TV on, the working strings will light up until the chip controlling the bad string flags a failure mode, shutting down the entire set to protection mode.

The exact same problem presented itself to me with a VIZIO set. I struggled thinking that it was a PS problem for two days, then finally realizing that the LED FAULT line was being pulled low (indicating a fault). It is very slow to respond (over 6+ seconds), thus giving the impression that the backlights are okay. However, the backlights were NOT okay and a teardown of the panel showed two LEDs out in one of the strings. I am waiting for LEDs to replace them.

Yea I understand that but it does it even went I have the back lights disconnected.
I have only power to the ps board and the ribbon from ps to the main and it still shuts down.
And if I jump 3.3v to ps-on the ps board stays on all with correct volts.
It just seems like a bad main board. But it is from shopjimmy.

[SLK001]

Re: Emerson LF501EM4F turn on then off.

The description sounds like you have bad LEDs in your backlight. There appears to be more than one string of LED power. When you turn the TV on, the working strings will light up until the chip controlling the bad string flags a failure mode, shutting down the entire set to protection mode.

The exact same problem presented itself to me with a VIZIO set. I struggled thinking that it was a PS problem for two days, then finally realizing that the LED FAULT line was being pulled low (indicating a fault). It is very slow to respond (over 6+ seconds), thus giving the impression that the backlights are okay. However, the backlights were NOT okay and a teardown of the panel showed two LEDs out in one of the strings. I am waiting for LEDs to replace them.