Samsung Hospitality HG32NB690PF x7 No Backlight

[Michale32086]

I got a lot in of Samsung Hospitality TVs... They all have the same problem.. They got power, they got sound, they got a picture, they just don't have any backlights..

Usually, if it's an LED strip issue, the LED strips will flash momentarily and that's it...

These are not doing that. Which indicates the Power PCB is at fault.. I find it hard to believe that 7 TVs would all have the same problem at the same time, but that's what it's shaping up to be...

I was hoping someone might be able to go over voltages with me and see if I can get just one working...

[attainteddragon]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

first thing that i would do is disconnect the cable that leads from ps to main, apply power and see if backlights come on.

next, check all voltages on the cable that go from ps to main and list for us all to see, in stby and when power is applied.

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

first thing that i would do is disconnect the cable that leads from ps to main, apply power and see if backlights come on.

next, check all voltages on the cable that go from ps to main and list for us all to see, in stby and when power is applied.

Thanx for the reply

No LED backlight when I unplug the cable between the PS and the MAIN board..

Voltages listed in pic

[budm]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

https://www.badcaps.net/forum/attach...2&d=1504617636
You need to measure the EVEN Column pins which are on the bottom side of the board or you can probe them on the backside of the connector. You have 14 pins total.
I.E. Pin 6 is BLU (BL-ON) signal pin as shown on the printed chart next to the connector.
We also need straight shot pictures of the top and bottom side of that power supply board.

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

https://www.badcaps.net/forum/attach...2&d=1504617636
You need to measure the EVEN Column pins which are on the bottom side of the board or you can probe them on the backside of the connector. You have 14 pins total.
I.E. Pin 6 is BLU (BL-ON) signal pin as shown on the printed chart next to the connector.
We also need straight shot pictures of the top and bottom side of that power supply board.

Thanx for the reply...

Pics attached..

2-DIM 3.1v
4-ECO 0V
6-BLU 5.1v
8-GND
10-GND
12-A5V 5.2v
14-PS 3.3v

All voltages were read when the TV is powered up..

[budm]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

Power supply board is BN44-00606A. Loaded LED power supply Voltage looks to to be 160VDC 320ma as printed on the board.
Put meter's probes between the two legs of the LED Boost converter filter cap C9102 then turn on the TV to see how high the DCV goes up to and settle down to after 5 seconds.
Pictures provided by shopjimmy.
http://www.shopjimmy.com/samsung-bn4...led-board.htm#
BTW, if you are going to work on lots of TV with LED backlights, you should get similar tool to this one:
http://www.shopjimmy.com/sid-gj2c-le...ght-tester.htm

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

Thanx for the reply BudM.. I am home now but will definitely check that voltage first thing in the AM..

And thanx also for that tool recommendation. I could definitely use that...

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

Power supply board is BN44-00606A. Loaded LED power supply Voltage looks to to be 160VDC 320ma as printed on the board.
Put meter's probes between the two legs of the LED Boost converter filter cap C9102 then turn on the TV to see how high the DCV goes up to and settle down to after 5 seconds.

The voltage at C9102 goes up to and holds steady between 121 and 123 volts...

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

OK I must have missed it the first time or not did something right..

I re-did the power up and the C9102 cap goes to 224V at power up and then goes down to a steady reading of 121-123 volts...

And I re-RE-did it and it shoots up to 229V and then counts down to 201V and then shoots back up to 229 and then counts back down to 201V rinse and repeat...

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

OK This is interesting...

I pulled a TV out that has been untouched... I cracked open the case and put my meter on C9102...

At standby, it registered a steady 107V.... At power up, it shot up to 223V, then counted down to 195-ish and then back up to 223-ish then counted back down to 195-ish, then back up and so on and so on and so on...

I pulled the LVDS cable from the Main Board, just for sheets and greens..

Power up the unit and it C9102 goes up to around 122-ish and hovers there...

[stj]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

the overshoot makes it sound like the leds arent connecting to the output - maybe one of those big resistors is bad.

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

the overshoot makes it sound like the leds arent connecting to the output - maybe one of those big resistors is bad.

Not sure if it has any bearing, but I also pulled the connector from the Power PCB to the LED array..

No change. Still holds steady at 120-ish with the LVDS cable detached and shoots up to 220-ish then back down to 195-ish with the LVDS cable attached...

[stj]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

instead of metering at the cap, meter at the led connector - i bet it's not getting there.

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

instead of metering at the cap, meter at the led connector - i bet it's not getting there.

Near as I can tell, 11-12 pins give me 9-12V.. All the rest are 0v

[stj]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

if you look at the tracks, there isnt much between the cap and the connector.
a quick look shows a big resistor on top, and a transistor under the board.
check the resistor first.

[budm]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

"Near as I can tell, 11-12 pins give me 9-12V.. All the rest are 0v" You need to use Black probe on the chassis, not on the 1-.

Pin 12 is connected directly to the + leg of the cap, the feeding Voltage to the boost converter is around 125V and it will go up over 200V if there is no load, so right now you should have 125V on pin 12. Pin 12 is the Anode pin of the whole LED string, the LEDs are connected in series, the Cathode return of the LED string is on pin 3 which is connected to the Drain pin of the PWM controlled MOSFET and the Source pin is connected back to ground through current sensing resistor R9110.
You can put Red probe on the Pin 3 of the connector and black probe on the chassis, if the LED string does not have open circuit then you should see Voltage jumps up for seconds.
More likely you have open circuit in the LED string which is common failure.

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

"Near as I can tell, 11-12 pins give me 9-12V.. All the rest are 0v" You need to use Black probe on the chassis, not on the 1-.

Pin 12 is connected directly to the + leg of the cap, the feeding Voltage to the boost converter is around 125V and it will go up over 200V if there is no load, so right now you should have 125V on pin 12. Pin 12 is the Anode pin of the whole LED string, the LEDs are connected in series, the Cathode return of the LED string is on pin 3 which is connected to the Drain pin of the PWM controlled MOSFET and the Source pin is connected back to ground through current sensing resistor R9110.
You can put Red probe on the Pin 3 of the connector and black probe on the chassis, if the LED string does not have open circuit then you should see Voltage jumps up for seconds.
More likely you have open circuit in the LED string which is common failure.

I have to say... It was a LOT easier checking Pin 12 when I figured it was just going to be 10-12V or so..

Pin 12 produces 200-224V at power up..

Pin 3 produces 1.3v and there is no jump at power up.......

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

if you look at the tracks, there isnt much between the cap and the connector.
a quick look shows a big resistor on top, and a transistor under the board.
check the resistor first.

My voltmeter is apparently wanky.. It says it's like 33ohm but then starts to fall...

[budm]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

I have to say... It was a LOT easier checking Pin 12 when I figured it was just going to be 10-12V or so..

Pin 12 produces 200-224V at power up..

Pin 3 produces 1.3v and there is no jump at power up.......

You have open circuit in the LED string.

[Michale32086]

Re: Samsung Hospitality HG32NB690PF x7 No Backlight

You have open circuit in the LED string.

So likely a bad LED strip??

Anyway to test it short of an LED Strip tester??

If not, any way to kludge something together until the one i ordered gets here??