Samsung LNT3253HX

[warhawk]

Have a Samsung LNT3253HX TV on which, the picture doesn't come one. Following is the sequencing and symptoms.

1) When plugged in, the RED Light Comes on.
2) When Power Button Pressed, Led Blinks twice and Blue Light Comes on. Following the light, two more led blinks and then LED goes off.

After the first two blinks, the screen flashes as if the picture is trying to come on, but then goes blank.

Looked at the capacitors on the main board and i don't see any bulging capacitors.

Would appreciate the help in trouble shooting this. I am handy with electronics, but never tried my hands on a TV, so might need some guidance.

[cadiman]

Re: Samsung LNT3253HX

Most likely the backlight inverter. Is that a darfon?

The inverter board may have a shorted mosfet or transformer or have an issue with the start up function. (looking for signal from power supply).

Caps, will only some of the time, be bulged when failed.

Anything 1000uf through 3300uf on the power supply I replace. I dont even test them. I know they are or will be a problem.

[budm]

Re: Samsung LNT3253HX

Pictures of the boards will help.

[warhawk]

Re: Samsung LNT3253HX

See attached pictures of the power supply and Inverter board.

I should also mention that the original owner had replaced the Power supply with another power supply as there was a annoying sound of the original.

Supposedly it worked fine for 2 months and then the TV would sometimes turn on, but other times the quick flash and off.

@ Cadiman - Not sure what you mean by darfon, but goggling it, i presume you are referring to some transformer ?

[budm]

Re: Samsung LNT3253HX

I hate to tell you this, but you are not suppose to remove the balck palstic piece which has the lamp sockets on it, the board is slided out off the black plastic piece which has sockets to make contact with the board. You will may ending up brekeing the lamp if you try to put that inverter board back in place.

[warhawk]

Re: Samsung LNT3253HX

That's how I was trying to remove it, but couldn't get it out. Anyways its back in and still the same issue. I think I got it back in without breaking it. Any way to test it?

[budm]

Re: Samsung LNT3253HX

Well, I do not know how you get ALL the lamps to seat into the sockets properly or without cracking the lamps. If one lamp is broken or not connect to the socket, the invert will go into shutdown to protect itself.
Can we see good close up pictures of the white connector of the inverter board? There are labels indicating the pinout of the connector that we need to verify.

[warhawk]

Re: Samsung LNT3253HX

1 to 5 - VIN
6 to 10 - GND
11 to 14 - ?

[budm]

Re: Samsung LNT3253HX

There are labels to the left side (by the white fuse) of the connector that show what the pin 11~14 are.
the Vin should have 24VDC when TV is power up.

[warhawk]

Re: Samsung LNT3253HX

11 - Error Out
12 - ENA
13 - DIM
14 - EX

So with the TV powered on, i do get 24.46V on Terminals 1 through 5.

[budm]

Re: Samsung LNT3253HX

Pin 12 should have >3VDC for ENA (BL_ON Backlights On) signal.
What do get at pin 11, 13, 14?

[warhawk]

Re: Samsung LNT3253HX

Well i was measuring the voltages, and now the TV seems to come on all the time. :S. Loose connection or something ?

[budm]

Re: Samsung LNT3253HX

May be it has loose lamp socket that did not make good contact with the lamp's terminal. Or loose connectiosn on the boards.
Just monitor those pins of the inverter board when it goes out again, at least write down tthe voltages on all the connectors of the power supply boards and the inverter board when the TV is off and when the TV is running so you will know what you should have if it fails again.

[warhawk]

Re: Samsung LNT3253HX

Really appreciate the help. Maybe it was a loose connection only, but time will tell.

I only measured the voltages with the TV Powered ON, so i am gonna leave the here for reference, in case i need to come back at this.

INVERTER BOARD
PIN 1 (VIN) - 24.45V
PIN 11 (Error Out) - 2.33V
PIN 12 (ENA) - 5.24V
PIN 13 (DIM) - 0.83V
PIN 14 (EX) - 0.01V