40" Samsung lnt4061f Vertical lines no backlight

[tieny]

Hey guys I have a lnt4061f samsung LCD TV. So here are the initial problems I'm seeing so far. I am able to turn the TV and it will turn on just fine however there is no backlight that goes on at all. I used a flash light on it and I can see color vertical lines all across the entire screen.

Also when I lay the TV face down with the screen facing down or place it upside down I hear the relay continuously clicking as soon as I plug in the power cable.

Is this TV even able to be fixed? Would the vertical lines point to a bad panel, though it covers the entire screen? I will put up some photos tomorrow.

[Mr Bill]

Re: 40" Samsung lnt4061f Vertical lines no backlight

The power supply in this model is full of capxon caps. When you open this tv up i'm sure there will be several bloated. The tcon could be failing causing the lines but a faulty power supply could do it too. I do have this exact model in my basement with a broken screen so if it needs a board atleast you'll know where to look

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Oh I forgot to mention, I already checked the capacitors on the power supply with my esr meter and they all seem to be good. Except that some of the traces seem to look damaged. I read that bad capacitors on this power supply actually caused the vertical lines on this tv. But what would cause the no backlight? I think I should fix the backlight problem first so I can get a better look at the vertical lines.

[Mr Bill]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Did you check the fuses on the inverter. 24v coming from the power supply?

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Can't seem to find any fuses on the inverter board. I feel this might be a power supply issue. Theres 12.1V from the output of the PSU going into the inverter board (Pin labeled VCC_12V). Also on standby I'm also not getting any reading on the pin labeled STB5.2V.

[budm]

Re: 40" Samsung lnt4061f Vertical lines no backlight

This TV has power supply/Backlights inverter combo board (high voltage transfromer on rhe botom left of the board), it will be a harder to troubleshoot. That long board on the left is the high voltage balancer board to ditribute the high voltage from the Power supply/inverter combo board.
There are connectors on the combo board, can you please show good closed up pictures so we can see the labels on them? The board is BN44-00167, need to look up the diagram for it. One palce to test right now is the DC voltage on that large cap in the primary side, check it when the TV is plugged in (it should be around 165VDC) and then when TV is turn on (it should be around 390~400VDC), this board has PFC Voltage booster circuits.
Diagram for BN44-00167A: http://www.tgohome.com/ServiceManual...g_BN44-00167A_[SCH].pdf

Check CN801 Pin 1 Power ON-OFF Voltage.
CN1803 Pin 1 Inverter ON-OFF Voltage

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

The large capacitor measures 163.3V when on standby and oscillated between 380 and 387V. On CN801 pin 1 (power on/off measures 0V both standby and when on. CN1803 where it says VCC12V measures 12.22V. I cant seem to open the link to the schematic.

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Oops i meant to stay the large capacitor oscillates between 380-387V when the TV is on. On CN801 pin 1 (power on/off) it measures 0.04V on standby and 2.79V when turned on. On pin 1 of CN1803 (Inverter on/off) I measured 0V when on standby and 5.2V when the TV is turned on. (Ignore what I said last post that was the wrong measurements) And I got the schematic to open =)

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Ok so i decided to disassemble it futher to check if it really has a bad panel or not before I waste my time trying to repair it.

I removed the LCD screen and shined my own light underneath it and this is what I see.
There are vertical lines across the entire screen however there are spots where it is just is black. The pattern doesn't seem to be even, since though some colored line strips are larger than others. Also whenever I turn off and turn it back on sometimes the pattern would change. (See the photos)

Also touching and pressing on the tab bonds doesn't seem to affect the picture in any way. I also tried pressing the menu and volume buttons on the side of the TV but also there was no change in the patterns

Also During the beginning as the TV turned on I also notice some horizontal lines within the vertical but it fades away after a couple of seconds (see the video link)
http://www.youtube.com/watch?v=TfsdY...ature=youtu.be

Would this be a bad panel? It doesn't look like the same problem Ive seen where the vertical lines just go across the entire screen.

[budm]

Re: 40" Samsung lnt4061f Vertical lines no backlight

You are getting correct control voltages and the PFC is working. As far as the panel concern, you need to see if the T-CON board is getting the voltage to it, check that on the surface mounted fues (both ends of the fuse) on the T-CON board.

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

I'm getting a reading of 13.1V on both ends of the fuse F1

[tom66]

Re: 40" Samsung lnt4061f Vertical lines no backlight

I had a vaguely similar problem with a Samsung - random vertical lines. However, I DID have a backlight. A voltage regulator on the t-con had failed.

[budm]

Re: 40" Samsung lnt4061f Vertical lines no backlight

It sounds like you have TWO problems, one in the inverter circuits, tow is either the T-CON or the main board (more likely to be the T-CON).

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Hmm I'm guessing I should solve the tcon problem first to make sure the picture is ok. So I should start by testing all the voltage regulators on the tcon board first?

[tom66]

Re: 40" Samsung lnt4061f Vertical lines no backlight

That would be a good start...

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Alright! so good news, I found a capacitor that was broken off the tcon, I was able to solder the pins back on in a werid way but it works. Turned on the TV and now I can see OSD menu and the white static when on the ANT input =) (except with no backlight).

Okay so next step is to figure out what is wrong with the inverter circuits.

When you say inverter circuits you mean the problem would be in the board of power supply/inverter combination? Would the problem be that high voltage transformer on the bottom left isn't outputing the voltages to the balancer board? I'll check diodes, but not sure how to check the mosfets

[budm]

Re: 40" Samsung lnt4061f Vertical lines no backlight

You need to check the MOSFET'S that drive the high voltage transformer first. Did you down load the diagram of the board?

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Yeah I was able to download it. How would you test a mosfet.

[budm]

Re: 40" Samsung lnt4061f Vertical lines no backlight

Check the fuse F1801 which is for the inverter output drive circuits.
It has 3 pins, so just mark the pins as 1, 2, 3.
Since we are looking for short (low resistance reading), just set the meter 200-Ohm scale and just measure:
1 & 2
1 & 3
2 & 3

[tieny]

Re: 40" Samsung lnt4061f Vertical lines no backlight

I'm guessing its the two mosfets right next to the transformer Q1801 and Q1802. Putting my probes on the suggested pins all read above the range of 200 ohms EXCEPT on Q1801 probe on pin 1 and 3 gives a measurement of 8.8 ohms. Suspect a short? (these measurements were taken in circuit) Both mosfets are labeled K3568 8:2