Samsung LNT4069FX/XAA no picture with sound

[ceconomon]

Samsung LNT4069FX/XAA no picture with sound

The set will power on and has sound, but no picture. For a period of time if the set warmed up for a bit you could power cycle it and get a picture. The power light flashes.

The power board has been recapped and the tconn board has been replaced. I would appreciate some guidance on this one.

[tom66]

Re: Samsung LNT4069FX/XAA no picture with sound

Check for a good 5V or 12V going to the T-con.

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

It makes sense to start at the power source.

I'm only seeing power on pin 3

PIN Exp. Actual
3 STB5.2V 5.22V
7,8 12V 0V
13,16 5.4V 0V
19,21,22 13V 0V

[budm]

Re: Samsung LNT4069FX/XAA no picture with sound

OK, you power supply board is a combo power supply and backlights inverter board.
You have backlights (your pictures show glowing screen), so inverter is working. You indicated that you do have sound, that does not make sense since the Audio amplifiers are running off either 12V or 13V power supply, but both of them are dead, no outputs as you have indicated. Can you please verify that again?

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

That was a duh moment. I had to have all the cables attached and power the set on before taking the measurements

PIN Exp. Actual
3 STB5.2V 5.22V
7,8 12V 12V
13,16 5.4V 5.35V
19,21,22 13V 12.73V

[budm]

Re: Samsung LNT4069FX/XAA no picture with sound

Ok, that is why you are getting sound. Now since you are getting backlights but no picture, then it can be that the T-CON is not getting either the 5V or the 12V (depends on T-CON board requirement) from the main board, or there are circuits failure on the T-CON board. So check the fuse and the voltages on the T-CON fuse first.

[electronicsurplus]

Re: Samsung LNT4069FX/XAA no picture with sound

Check the fuse on the t-con. it is a small white surface mounted fuse. usually marked with fxxx. if this fuse is good measure between the fuse and ground to ensure that you have 5V there. make sure to check both sides of the fuse for 5v. The fuse is located just above the LVDS connector horizontal.

If you have 5v on both sides of the fuse then you have a bad T-con, which on some can be repaired by replacing the voltage regulators, which are also surface mounted. you can also check the mosfets on the board. if they are good then you have bad IC and, probably best to but a new t-con. they are only approx $60 or so @ shopjimmy.com, retechtv.com and, of course, us and many other sites

This is a very common problem with this Samsung model

Jon

Electronic Surplus

Sometimes, there are also bad caps on the

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

I'm not seeing any voltages listed on the t-conn or the FRC board. The main board has some and they are not what they should be.

Pin Expected V Actual V
2 9v 2.05v
4 5v 0.04v
6 33v 0.04v
16 1.2v 1.24v

I don't see a surface mount fuse anywhere on these board. I saw a picture of one in your troubleshooting guide.

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

I found the fuse on the t-conn and it's good.

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

Let me clarify. The fuse is good. I'll figure out where to measure the voltage the electronicsurplus mentions.

[budm]

Re: Samsung LNT4069FX/XAA no picture with sound

DC volt, Black probe on the TV chassis, red probe on either ends of the fuse of the T-CON board.

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

12.6V on both sides of the fuse.

[budm]

Re: Samsung LNT4069FX/XAA no picture with sound

OK, there are voltage regulators and switching power supplies on the T-CON board, we will need good clear pictures of the board so we can tell you which one to check.
This still does not make sense since you have indicated that you had already replaced the T-CON board. Do you still have the old one, and what was the original problem with the TV?

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

I do have the original t-conn board and I placed it in the set today and it produces the same result as the replacement board. With both t-conn boards I do observe a flicker every 4 seconds.

The issue with the TV was that it would show the cloudy screen and after it warmed up you could power cycle it and get a picture. My parents would leave the TV on all day since it was a pain to get going. They tell me at times the set would go off (they would hear the power cycle tones this set makes) and you would get the cloudy screen again.

[budm]

Re: Samsung LNT4069FX/XAA no picture with sound

It sounds like you have more than one problem: TV cycle on/off, no pictures on the screen (it may be related).
Your T-CON has a lot of switching power supplies, you can also see voltage test points on the board. Common failures are due to shorted out caps, failed regulator, blown fuse.
MOMAKA is an expert at T-CON, he may be able to tell you what voltage you should see at those test points.

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

Here are the voltages on the T-CON test points.

new T-CON
VREF 2.387v
VDOMO 2.519v
VDOQO 2.521v

old T-CON
VREF 2.396v
VDOMO 2.528v
VDOQO 2.530v

As of now, I'm not seeing the power cycle problem, just a white screen with sound.

I sent momaka a msg. I'm hoping he has time to look at my post.

[retiredcaps]

Re: Samsung LNT4069FX/XAA no picture with sound

There are several voltage regulator and/or DC/DC converters circled in red.

To test a voltage regulator, plug in your device and power on.

1) Set your multimeter (if manual range) to 20V DC.

2) Put your black probe on a ground screw. Leave it there the entire time. This is your ground.

3) Put your red probe on each of the pins including the "cut" pin, but ignore the "fat" tab. The fat tab is "up" or "north". Number the pins left to right.

4) Report them like so along with the part number (include all lines on the IC) of the IC.

U100
AS1117-33
pin 1 = 0.0
pin 2 = 3.3
pin 3 = 5.0

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

I've labeled the picture for reference (arrow to pin1) and below are the results.

location -IC103
SPX1587AT
0741LC
pin 1= 1.284
pin 2= 2.535
pin 3= 5.31

location -IC107
SPX1587AT
0741LC
pin 1= 2.046
pin 2= 3.298
pin 3= 5.31

location -IC110
SPX1587AT
0741LC
pin 1= 0.0
pin 2= 1.25
pin 3= 3.277

location -IC112
17-25
0739AG
pin 1= 0.0
pin 2= 2.504
pin 3= 5.29

location -IC102
17-33
0739BG
pin 1= 0.0
pin 2= 3.284
pin 3= 5.17


location -IC102 FRC board
37302WU
0735
pin 1= 3.422
pin 2= 3.423
pin 3= 0.0
pin 4= 2.478
pin 5= 1.24


location -IC102 FRC board
37302WU
0735
pin 1= 3.421
pin 2= 3.421
pin 3= 0.0
pin 4= 1.836
pin 5= 1.262

[retiredcaps]

Re: Samsung LNT4069FX/XAA no picture with sound

location -IC102 FRC board
37302WU
0735
pin 1= 3.421
pin 2= 3.421
pin 3= 0.0
pin 4= 1.836
pin 5= 1.262

You have IC102 listed twice. Whatever the above is, I suspect pin 4 is too low.

According to

http://datasheetz.com/data/Integrate...atasheetz.html

If the above is an adjustable regulator, it should be pin 5 + 1.25V or 1.262 + 1.25 = 2.512V DC for output. At 1.836V, pin 4 is too low.

Now if the part number for the above indicates it is a fixed 1.8V regulator, then it is good.

So doublecheck IC102 and IC107 as to which is which and redo the measurements

[ceconomon]

Re: Samsung LNT4069FX/XAA no picture with sound

I double checked the measurements and corrected the location.
--------------------------------
location -IC102 FRC board
37302WU
0735
pin 1= 3.417
pin 2= 3.417
pin 3= 0.0
pin 4= 2.478
pin 5= 1.241


location -IC107 FRC board
37302WU
0735
pin 1= 3.415
pin 2= 3.415
pin 3= 0.0
pin 4= 1.847
pin 5= 1.265


Base on your analysis, it looks like I should be ordering the following part:
http://www.digikey.com/product-detai...6-5-ND/1029402