SAMSUNG UN37EH5000FXZA No BL or Pic

[mike123333]

Hello everyone,

I have a Samsung UN37EH5000FXZA TV that will not power up an give me the video and black light. The Front LED is on and the TV will cycle but the back light doe snot come on.

Here is my diagnosis so far, the voltage coming ou fo the PSU and to the mainboard are all good. I have the 12.9 V and 5.2V where needed. The power stays on for about 30 secs then shuts down ( no pic or backlight). If I disconnect the harness from the PSU to the mainboard the back light comes on. The other troubleshooting I have done is with cold and warm temperature. If I place the main board in the frig I get the same symptoms. If I use a hair dryer or hot air station and put heat to the board, say near large IC or others IC or even the ground the TV comes on and stays on. I have tied to heat up the large IC and re-solder many of the components on the board to see if there is a colder joint, but cannot seem to find the culpit. I am no sure if I have a BGA solder issue on the large IC an requires reballing?

I am at a lost, so far it seems that the mainboard has an issue, but do not know what it is.

Any help would be greatly appreciated.

Thanks,

Mike

[budm]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

https://www.badcaps.net/forum/attach...7&d=1544149050

1) How about reporting all the Voltage of all the pins on that connector that goes to the main board, you indicated you have 5V and 12V but you did not provide any Control Voltage readings.
2) If you run the power supply board without having the cable between power supply board and the Main board connected, do the backlights come on and stay on as long as the TV is plugged into the AC outlet.
3) Read the basic TV troubleshooting guide.

[mike123333]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

https://www.badcaps.net/forum/attach...7&d=1544149050

1) How about reporting all the Voltage of all the pins on that connector that goes to the main board, you indicated you have 5V and 12V but you did not provide any Control Voltage readings.
2) If you run the power supply board without having the cable between power supply board and the Main board connected, do the backlights come on and stay on as long as the TV is plugged into the AC outlet.
3) Read the basic TV troubleshooting guide.

The voltages from top to bottom are Zero with no power and the red led is on.
with power the voltages are as folows:
12.9
12.9
12.9
12.9
gnd
5.2
5.2

when the cable is disconnected between pSU an main board the back light comes on and stay on as long as the TV is plugged in.

I do not feel any hot ICs that trigger any shorts.

[budm]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

The voltages from top to bottom are Zero with no power and the red led is on.
with power the voltages are as folows:
12.9
12.9
12.9
12.9
gnd
5.2
5.2

when the cable is disconnected between pSU an main board the back light comes on and stay on as long as the TV is plugged in.

I do not feel any hot ICs that trigger any shorts.

Please look real close at the board, you can see the printed pin names assigned to each pin of that connector which has 14 pins, you are not reporting all the pins.
So please put down the pin names and follow by the Voltage reading for each pin.
I.E.
Pin 1 B13V = xx V
Pin 2 PWM_DIM = xx V
Right now the power supply board and the Backlights are OK.
The exposed pins you see on the top side are ODD number pins, to get the reading of the Even number pins you will need skinny probe into the wire entrance side of the connector.

[mike123333]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

Please look real close at the board, you can see the printed pin names assigned to each pin of that connector which has 14 pins, you are not reporting all the pins.
So please put down the pin names and follow by the Voltage reading for each pin.
I.E.
Pin 1 B13V = xx V
Pin 2 PWM_DIM = xx V
Right now the power supply board and the Backlights are OK.
The exposed pins you see on the top side are ODD number pins, to get the reading of the Even number pins you will need skinny probe into the wire entrance side of the connector.

Got it figured on the voltages:

Pin Off , On
1 B13V 0V , 12.94V
2. PW_DIM 0V , 0.089V
3. B13V 0V , 12.94V
4. B13V 0V , 12.94V
5. Vamp 0V , 12.94V
6. BLU_0n/off 0V , 0.062V
7. Vamp 0V , 12.94V
8. GND 0V , 0.015V
9. GND 0V , 0V
10. GND 0V , 0.015V
11. B5V 0V , 5.23V
12. A5V 5.24 , 5.24V
13. B5V 0V , 5.23V
14 Power on/off 0V , 3.51V

it looks like the back light voltage is no present.

[budm]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

2. PW_DIM 0V 0.089V: Bad, no backlights dimming command from the main board.
6. BLU_0n/off 0V 0.062V: Bad, no backlights on command from main board. ON = 2V or higher.
So you need to troubleshoot the main board next. I do not how much experience you have to troubleshoot complex main board.

[mike123333]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

Thanks BUDM
I will give it a try, I do have an oscilloscope where necessary, the only question I have is why when I heat up the board the TV functions? I could purchase a main board but I want to learn more before I throw in the towel.

[budm]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

You need to do localize heating as much as you can to at least pin point the location of the bad section of the board.

[mike123333]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

You need to do localize heating as much as you can to at least pin point the location of the bad section of the board.

I have spent sometime time trying to troubleshoot this issue to no availability. I managed to locate a service manual but that was not much of a help as it was not detailed, I am not sure if there is a detailed SM. I am unable to trace back the backlight connections on the board. Any ideas where I can focus, this is not a cut and dry troubleshooting without a schematic to follow.

Thanks,

MJ

[budm]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

Without schematic that matched your board it will not be easy work, you can spend lots of times on it and may not getting anywhere with it but that how it goes sometime.
You may try locating some Voltage test points or locate Voltage regulator ICs and check the Voltages when the TV is working and when TV is not working.

[nomoresonys]

Re: SAMSUNG UN37EH5000FXZA No BL or Pic

One there has make offer option too. https://www.ebay.com/itm/SAMSUNG-MAI...O~J:rk:37:pf:0