Sony Bravia no Picture

[tlm387]

I am new here and I picked up a free a Sony Bravia KDL-46V4100 from craigslist that I am trying to bring back to life. Therefore I dont have any back story as the symptoms the TV had before it went out. I'll start by explaining what I have discovered so far.

1. The tv powers on with a solid green power light and responds to the remote.
2. The tv does not show any blinking red trouble-shooting light
3. The backlight and sound work on all of the inputs
4. There is absolutely no picture, there are no menus, guides, or video feed what so ever

From research on this forum I decided the best place to start would be to replace the t-con board. I ordered a board on ebay and installed it tonight to no avail. The tv demonstrated the exact same conditions.

Then I got brave and decided to see what would happen if I powered up the TV without the t-con board and the tv did exactly the same thing that it did with both the original and the replacement t-con boards.

This makes me think the either both t-con boards are bad or the lcd display is completely dead. Which leads me to a couple of questions.

Is there a chance the display is dead, and is there a way to test it?
How can I verify that both t-cons are in fact dead?
Is there another component I should investigate here?

It seems strange they both would exhibit the exact same conditions. And that the tv behaves in the same manner with or without the t-con installed.

Thank you for your help. Any input is greatly appreciated.

[rayrod81]

Re: Sony Bravia no Picture

The fact that you ordered the board on ebay raises a red flag for me. Many of the boards are not tested and are advertised as being pulled from a tv with a broken screen. Unless it was purchased from someone that has a near perfect feedback rating and deals only in tv parts then I would not trust the board as being good. If it is in fact good then you either have a problem with the voltage being sent to the panel from the main board or power supply or it is a bad LCD panel and the tv is only good for parts.

[tlm387]

Re: Sony Bravia no Picture

I bought the replacement board from ebay user tonyatford/House of Gadgets. It was listed to be in 100% working condition. And the return policy backs this up. The seller has a 99.4% feedback rating. I will ask him today what method he uses to test components.

How can I test if there is voltage coming from the Input Board and or Power Supply and going to the T-Con/LCD?

[rayrod81]

Re: Sony Bravia no Picture

There should be a connector going from the power supply to the T-Con board. I would measure voltage on the power supply side. Measure with and without the T-Con attached. Without pictures I can't help you more than that.

[tlm387]

Re: Sony Bravia no Picture

The LVDS cable runs from the t-con to the main input board. When testing voltage on the LVDS cable where should I place the negative lead of the multimeter?

I get the feeling that there is no power going to the t-con because the tv behaves the same with or without a t-con plugged in.

[cadillacman]

Re: Sony Bravia no Picture

Those kdl series sonys are known for super kraptastic lcd panels. The ribbon cables that go form the glass part to the circuit board lose connecton and get intermittent, etc.

Im not saying thats whats wrong, but therea a good chance.


Try to gently flex the tv one way then power on.. if nothing try gently flexing the other and try again.. most of the time that will get it up an going but because of the krappy connections the picture will get all acid trippy and slow to respond.

If you do have tab bonding issues, you can do what i did... ill post a link to my posting in a few mins...


Ahh here it is. Also before you go through all that make sure to check all your voltages and make sure you dont have a power issue or something else simple before you dig into the panel itself.

[PlainBill]

Re: Sony Bravia no Picture

I bought the replacement board from ebay user tonyatford/House of Gadgets. It was listed to be in 100% working condition. And the return policy backs this up. The seller has a 99.4% feedback rating. I will ask him today what method he uses to test components.

How can I test if there is voltage coming from the Input Board and or Power Supply and going to the T-Con/LCD?

I have seen vague references to a technique for putting a tcon in test mode. I don't have any more details, but that should be one way to isolate the problem.

PlainBill

[tlm387]

Re: Sony Bravia no Picture

Ok well I found a pin on the t-con labeled "IN" and it runs straight into one side of the 3A pico fuse. So I took a voltage reading at that point and im only getting .16 volts.

Based on this I'm assuming that the tcon is not getting enough juice to function. So I figure it must be something wrong with the BU input board, or the power supply. Would this be a valid/accurate assumption?

Is there a sure fire way to tell if the power supply is putting out enough voltage to the input board? Where should I test and how much voltage should I expect?

As far as the tab bonds, I have already dug into the lcd and tried applying pressure to the tab bonds with no results. The screen stayed completely dark (backlight only). Until I can get the tcon functioning I dont have a way to assess the tab bonds.

I'll add pictures of the Power Supply and Main Input board when I can get a hold of my good camera, and some good sunlight

[tlm387]

Re: Sony Bravia no Picture

UPDATE:

I just found the service manual for this model. And the schematics were helpful. I am a novice at all this so I am probably missing a lot of important details provided by the schematics. I found something important.

I am getting just shy of 12vDC on each of the three 12v leads going into the input board. I suspect this means the power supply is functioning properly.

[santel]

Re: Sony Bravia no Picture

Wrong, you should have 60 to 90 Volts DC. In the power board check the voltage (DC) on the across the big capacitors. Do you hear a click upon powering the set? Do you have sound? If you don't is very possible that the the power board is bad.

[PlainBill]

Re: Sony Bravia no Picture

Wrong, you should have 60 to 90 Volts DC. In the power board check the voltage (DC) on the across the big capacitors. Do you hear a click upon powering the set? Do you have sound? If you don't is very possible that the the power board is bad.

tlm387 is right, you're wrong. There is no point on an LCD TV that I would expect to find 60 - 90 VDC.

PlainBill

[tlm387]

Re: Sony Bravia no Picture

Just to be certain, does anybody know how much voltage I should expect to see going into the t-con?

[PlainBill]

Re: Sony Bravia no Picture

Just to be certain, does anybody know how much voltage I should expect to see going into the t-con?

I would expect to see either 5V or 12V going into the tcon. 0.16 Volts is much too low. I would trace the supply line back to the main board.

PlainBill

[cadiman]

Re: Sony Bravia no Picture

I have 12v on a kdl 32xbr4. A grey panel is a blown fuse on t-con board.
I would not trust a used t_con. They all seem to be bad or going bad with Sony.

What I am having trouble with is some of these sonys are repaired with a new t-con board (not a used one) and some are not repaired by replacing the t-con board.
I don`t see how a whole panel can fail and I think people are buying bad t-con boards from ebay that people think have a faulty panel.

I am pretty sure it is a t-con failure. The problem is a new one is very expensive.

I have read more info on faulty t-con boards than bad panels on Sony.

I wish I had a working sony xbr to test this theory.

[mbates14]

Re: Sony Bravia no Picture

I work on these stupid sonys all the time.

there is a VERY EXTREMELY SUPER MINI TINY fuse on the signal board that popped when the t-con went bad. I am thinking smaller than SMD0603
you must replace this fuse. This fuse supplies the 12V to the T-con board, and if popped, you will get no 12V to the panel.

These boards are riddled with tiny fuses. id say theres maybe 5 to 10 of them in various circuits. there is one popped, and i think its near the center of the board on the back side.

[cadiman]

Re: Sony Bravia no Picture

That would be why tvs don`t work after replacing the t-con board?

This happens to me every time I think I learned a bit more than the day before... then a different model tv kicks my butt and I start all over again.

I should have been a doctor. They get to work on the same model day after day.

[Scenic]

Re: Sony Bravia no Picture

I should have been a doctor. They get to work on the same model day after day.

[tlm387]

Re: Sony Bravia no Picture

I work on these stupid sonys all the time.

there is a VERY EXTREMELY SUPER MINI TINY fuse on the signal board that popped when the t-con went bad. I am thinking smaller than SMD0603
you must replace this fuse. This fuse supplies the 12V to the T-con board, and if popped, you will get no 12V to the panel.

These boards are riddled with tiny fuses. id say theres maybe 5 to 10 of them in various circuits. there is one popped, and i think its near the center of the board on the back side.

Yeah I spent some time testing the fuses that I could find. I found a 5A 24V micro fuse type 1608 (Sony part #1-576-933-21) that I just could not get continuity from so I thought I found the problem. I jumped the fuse with a dab of solder, but all that happened was a rely clicking on and off until the standby light flashed a main board error.

So i un-soldered the jumper and the tv went back to behaving as it did in my first post.

For the record I have checked the fuse on the t-con and its appears to be fine.

Rather than run the risk of damaging the tv further by jumping fuses that have blown for a reason, I went ahead and ordered a replacement main board from MAT Electronics. I'll post my results when it arrives. Any body have experience with this company? I'm a little concerned because I never received a conformation email.

[tlm387]

Re: Sony Bravia no Picture

I GOT THE SUCKER WORKING!!!!

Apparently I did I bad job on my jumper solder job, when i did it I just did a visual inspection to see that I had bridged blown fuse, being the size of a small bread crumb I should have tested for continuity. (Among other potential problems)

So going back over the schematics I re tested all the fuses on the main (input) board. There are a 6 fuses listed on the schematics. There is a fuse called F1422 (5A 24V) which powers the TPC8109(TE12L) chip. This chip then runs out to the display. At least that is what I am interpreting from the attached schematic. After my jumper job I still was not getting continuity from this fuse, so I redid the solder connection and tested again for continuity and the test was positive. I made sure I did the best solder job I could with a my $9 dollar radio shack soldering iron and no magnifying glass. This time I removed the F1422 and just soldered the two points on the board together.

I plugged it all back in and it worked. I'm shocked that a $.95 cent fuse which is smaller than...most things I've ever seen, knocked out this whole tv. Seeing as how that fuse blew for a reason, I'm still going to run the replacement board once it arrives. But I'm glad to know why this tv stopped working.

Now if I could just figure out what blew that fuse...

Anyways I owe it to you all for helping me brainstorm through this process. MUCH THANKS!

[PlainBill]

Re: Sony Bravia no Picture

I GOT THE SUCKER WORKING!!!!

Apparently I did I bad job on my jumper solder job, when i did it I just did a visual inspection to see that I had bridged blown fuse, being the size of a small bread crumb I should have tested for continuity. (Among other potential problems)

So going back over the schematics I re tested all the fuses on the main (input) board. There are a 6 fuses listed on the schematics. There is a fuse called F1422 (5A 24V) which powers the TPC8109(TE12L) chip. This chip then runs out to the display. At least that is what I am interpreting from the attached schematic. After my jumper job I still was not getting continuity from this fuse, so I redid the solder connection and tested again for continuity and the test was positive. I made sure I did the best solder job I could with a my $9 dollar radio shack soldering iron and no magnifying glass. This time I removed the F1422 and just soldered the two points on the board together.

I plugged it all back in and it worked. I'm shocked that a $.95 cent fuse which is smaller than...most things I've ever seen, knocked out this whole tv. Seeing as how that fuse blew for a reason, I'm still going to run the replacement board once it arrives. But I'm glad to know why this tv stopped working.

Now if I could just figure out what blew that fuse...

Anyways I owe it to you all for helping me brainstorm through this process. MUCH THANKS!

Well, the answer won't give you a lot of comfort. That circuit is the switch supplying power to the panel. Nothing on this section of the schematic could cause the fuse to blow, even if it shorted out. The conclusions are a tcon or panel drawing too much current, or a defective fuse. If you notice the shaded triangle with the ! next to the fuse, that fuse is a safety item.

PlainBill