Funai (Emerson) LF501EM4F not turning on

[dick_barton]

Re: Funai (Emerson) LF501EM4F not turning on

LCD Panel name and #?? Where do i find that.

On the back of the LCD panel stuck normally on a white label to the metal chassis.

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

On the back of the LCD panel stuck normally on a white label to the metal chassis.

Panel Sticker Number: U3AU1XH

CN1001 TO LCD PANEL ASSEMBLY Tested with ground to GP001
1 VLED1=47vdc
2 ILED1=.006vdc
3 VLED2=77vdc
4 ILED2=.074vdc
5 VLED3=76.5vdc
6 ILED3=.074vdc

[dick_barton]

Re: Funai (Emerson) LF501EM4F not turning on

Those readings above would indicate a faulty Vled1 string. I have to be honest but I'm now out of ideas.

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

Those readings above would indicate a faulty Vled1 string. I have to be honest but I'm now out of ideas.

Sorry I didnt mention it quick i was taking reading again ABOVE TEST WAS Power board+led forced on


For some reason PROTECT 3 shows .075 at all spots and drops down to .017 when bl is forced on

POWER BOARD+LED +MAIN BOARD (NORMAL) TEST NO JUMP NO FORCE ON
1 VLED1=47vdc
2 ILED1=.001vdc
3 VLED2=47vdc
4 ILED2=3.8vdc
5 VLED3=47vdc
6 ILED3=2.5vdc

POWER BOARD+LED+MAIN (NORMAL HOOKUP+BACKLIGHTS FORCED ON) PROTECT 3=.075 Still
1 VLED1=47vdc
2 ILED1=.006vdc
3 VLED2=77vdc
4 ILED2=.74vdc
5 VLED3=76.5vdc
6 ILED3=.75vdc

[dick_barton]

Re: Funai (Emerson) LF501EM4F not turning on

I still believe you have a VLed1 problem. As Budm said in an earlier post when the mainboard is not connected the Protect3 is not activating backlight shutdown.

In Post#35 you said you forced it on and all the leds were working. So you removed the panel and checked the leds visually?

[budm]

Re: Funai (Emerson) LF501EM4F not turning on

Sorry I didnt mention it quick i was taking reading again ABOVE TEST WAS Power board+led forced on


For some reason PROTECT 3 shows .075 at all spots and drops down to .017 when bl is forced on

POWER BOARD+LED +MAIN BOARD (NORMAL) TEST NO JUMP NO FORCE ON
1 VLED1=47vdc
2 ILED1=.001vdc
3 VLED2=47vdc
4 ILED2=3.8vdc
5 VLED3=47vdc
6 ILED3=2.5vdc

POWER BOARD+LED+MAIN (NORMAL HOOKUP+BACKLIGHTS FORCED ON) PROTECT 3=.075 Still
1 VLED1=47vdc
2 ILED1=.006vdc
3 VLED2=77vdc
4 ILED2=.74vdc
5 VLED3=76.5vdc
6 ILED3=.75vdc

If you look at the schematic, the 47VDC reading with all the board connected is correct, that is feeding Voltage to LED Boost Converter circuit.
when you force on the PS-ON and BL-ON then the boost converter circuit will and give you that 78~82VDC out put. Right now the boost converter for LED1 is not working, per diagram it should be around 82V.
So it can be that too much load is being seen due to shorted out LED, or LED has open circuit so the Voltage shot up to higher than 82V so it shutdown the boost converter.
You need to leave the probe on VLED1 and then force on the board to see how high the VLED goes up to.
"PROTECT 3=.075 Still" that is because there is problem so the line is held LOW.

BTW:

i got bored and opened it up all leds came on when forced on

This cannot be true since 47V IS NOT enough to light up the LED string if that is what you are actually seeing.
I hope we are not doing goose chase due to wrong DATA and information!

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

If you look at the schematic, the 47VDC reading with all the board connected is correct, that is feeding Voltage to LED Boost Converter circuit.
when you force on the PS-ON and BL-ON then the boost converter circuit will and give you that 78~82VDC out put. Right now the boost converter for LED1 is not working, per diagram it should be around 82V.
So it can be that too much load is being seen due to shorted out LED, or LED has open circuit so the Voltage shot up to higher than 82V so it shutdown the boost converter.
You need to leave the probe on VLED1 and then force on the board to see how high the VLED goes up to.
"PROTECT 3=.075 Still" that is because there is problem so the line is held LOW.

BTW:
This cannot be true since 47V IS NOT enough to light up the LED string if that is what you are actually seeing.
I hope we are not doing goose chase due to wrong DATA and information!

YEs stop the chase . led string is out now opened back up the voltage jumps when connected first moment plugged in to 60vdc very dim for a split second and fades out voltage goes back to 47v So my problem is somewhere in the actual led string ?

[budm]

Re: Funai (Emerson) LF501EM4F not turning on

You can try swapping the suspect bad string to see if it will follow.

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

You can try swapping the suspect bad string to see if it will follow.

Sure does follow, led string Light fine on other driver

[budm]

Re: Funai (Emerson) LF501EM4F not turning on

Sure does follow, led string Light fine on other driver

I am confused, so you move the string that was dimmy lit to another diver and it lights up fine?

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

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I am confused, so you move the string that was dimmy lit to another diver and it lights up fine?

YES CORRECT ALL LED LIGHTS ARE FINE. NO LIGHTS UNDER VLED1 when swapped with others. I did unplug the power between swaps

It seems something was already bad to flag an error and forcing the unit on killed the issue in that circuit the rest of the way?

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

OKay so I followed flow chart no.3 of no picture and tested CN501 Pin 20-23 IF i labled correclty? could not find any mark besides pin one on CN501
(Should read 21v for Pin 20-23
Pin 23,22 read 21volt
Pin 20,21 read 11.8v

Pin 8 was checked just to be sure 3volt as it should

cathode of D650 read 21volt as it should

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

not sure if i guessed the pinout correctly. I searched all over for some sort of key in the schematic. the last 4 do read 21v if it was counting up and down rather then straight across. still out light from led 1 just low voltage at what ever strip its hooked to . no wire fault

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

not sure if i guessed the pinout correctly. I searched all over for some sort of key in the schematic. the last 4 do read 21v if it was counting up and down rather then straight across. still out light from led 1 just low voltage at what ever strip its hooked to . no wire fault

ALright i did some poking around before I put it to the side for a bit. Q1102 may be toast? It does not test the same as Q1202,Q1302(tested exact same) shouldn't they read the same on tester or volt meter being the 3 circuits are identical test were done off

voltage at source pins of those 3. Q1202+Q1302 start at about 10.5 drop to 9.5 quickly.. Gate Q1102 Starts 11.5 then drops to .006 after a few moments

what is acceptable replacement few part board still to look at but i have a few no match yet ?

[dick_barton]

Re: Funai (Emerson) LF501EM4F not turning on

You can check the mosfet. There are plenty of Youtube videos on how to test. If it tests OK then there may be a drive problem with IC1101

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

You can check the mosfet. There are plenty of Youtube videos on how to test. If it tests OK then there may be a drive problem with IC1101

it checked bad these schematics are difficult somewhat...is there parts i can use to bypass or 2 to use maybe i can find easier? Other than order or find another of same model? either to verify rest of set is working correct

[budm]

Re: Funai (Emerson) LF501EM4F not turning on

If I were you I would remove R1108 (1K) connected to pin 7 (ERROR) OF of IC1101 which is the LED driver for the VLED1, this will stop the VLED1 circuit from pulling PROTECT3 low. You will now have only two sets of LEDS working and the TV should function unless it has more than one problem.

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

If I were you I would remove R1108 (1K) connected to pin 7 (ERROR) OF of IC1101 which is the LED driver for the VLED1, this will stop the VLED1 circuit from pulling PROTECT3 low. You will now have only two sets of LEDS working and the TV should function unless it has more than one problem.

worth a shot.. removed it plugged in main board and full power at rails did not push power no black lights so jumped all besides ps-on protect 3 =.5v

[jayjoesph]

Re: Funai (Emerson) LF501EM4F not turning on

i think its bout time to give up lol. Was hoping to purchase the main board if anything

[budm]

Re: Funai (Emerson) LF501EM4F not turning on

One of the three IC is pulling down that PROTECT3, the output n pin 7 is Open Drain output so all three error lines are connected as an OR set up, there is resistor at pin 7 of each IC, you might as well remove them all to see if PROTECT 3 will go HIGH.