Sony KDL-40BX400

[wwanderer]

Hi to all

I am going to replace the TCON board .Does anyone had the same problem?

Sound: ok
Inverter backlights:ok
Picture: small flashing screen raster colored pattern rolling horizontally on the
upper part of the screen

(See the attached picture)

[keeney123]

Re: Sony KDL-40BX400

If you search for this on badcaps it will tell you all you should need for this problem
LCD TV and Monitor basic troubleshooting guides
by BudM

[wwanderer]

Re: Sony KDL-40BX400

I read the pdf files you mentioned.

I tried to test he TCON board, with the removal trick of the flat cable board between Main board and TCON board.

Now, the standby led flashes 5x times and the TV stops.

No sound
No picture
No light from inverter.

Panel problem?


I removed the TCON board but the TV produces the same 5x led standby protection mode.

Any advice?

Thank you.

[keeney123]

Re: Sony KDL-40BX400

I'm not an expert like some of these guys are, but to me it looked like a panel problem. Of course the correct way to go about a problem is don't assume anything. If you step through that basic guide. First with the voltage etc. and then with the other procedures. The problem with the panels is that they have gate drivers that run down the side of the panel. These are built-in to the panel. If one of them screws up than it will screw up the rest of the picture and there is nothing that can be done. Perhaps one of these other guys who work on this stuff everyday will help you.

[newtothis]

Re: Sony KDL-40BX400

Looks like a panel failure to me I'm afraid

[wwanderer]

Re: Sony KDL-40BX400

Thank you all for your answers.

Now the questions are:

1.Is it possible to test or the panel in order to be certain that this is the problem?

(When I made the removal trcick of the LVDS cable some pins were damaged and maybe for this reason the mainboard failed too.Wishful thinking..)

2.If I change the mainboard, the TCON and the damaged LVDS flatcable between the TCON and the mainboard and the panel has problem will these two boards be ruined?

I can't measure any voltages in these two boards because the TV shuts down in 3 seconds and then there is the 5 blinking code.

Any more suggestions?

[keeney123]

Re: Sony KDL-40BX400

I am sure there must be a way to disconnect the cables to the power supply board to find out if the power supply is good. The power supply I believe has to be forced on by jumpering some connector to PSON. Even thou the picture shuts down you may also be able to read some voltage on the regulators. Also, do you have a cable going from the TCon board to the panel? What the TV guys are going to want from you is close up pictures of your boards and how they are laid out. Perhaps if you did that you would get more responses. I just do not repair these on a regular basis and I do not keep all that stuff in my head. If you are going to be repairing these on a regular basis than it would benefit you to post the pictures and be guided by some of these guys that are experts at doing this. Even if it is the panel the value you will gain from stepping through the procedures would be of great be benefit. I would say only if your going to use this knowledge more than three times.

[budm]

Re: Sony KDL-40BX400

I would at least check to see if the SMD fuse on the T-CON board is still good.

[wwanderer]

Re: Sony KDL-40BX400

The smd fuse on the TCON is ok.

I have disconnected the TCON cable from the main board.The TV shuts down with the 5 led blinking code.

Can I force on the power supply unit?

Can I make any oher test in order to be certain that this is a panel problem?


Thank you

[budm]

Re: Sony KDL-40BX400

Are you getting 12VDC at both end of the fuse with ref to the chassis?
There are Voltage regulator ICs and 3 switching power supplies on that T-CON board, also test points for Voltages that should be tested.

[wwanderer]

Re: Sony KDL-40BX400

Thank you budm for your answer.

Finally I am back to my first post.(The LF7 in position PS6401 on Power Supply Unit was open circuited).

Now:

TV turns on.
Sound ok.
Picture: see the attachment in my first post

I am getting 12.7 VDC at both end of the fuse on the TCON ,with ref to the chassis.

1.What test points for Voltages should I test on the TCON board?Any schematic?

2.In general, this model of Sony (Bravia) has problematic lcd panels?

So as I understand we can't check the panel.For this reason, we check the other parts.

3.If they are ok then it is a panel issue and we can't do anything?

[budm]

Re: Sony KDL-40BX400

Try disconnecting the ribbon cables between the T-CON and the LCD panel to see if the 5-blink error code goes away if you have not done that yet.

[wwanderer]

Re: Sony KDL-40BX400

I disconnected the ribbon cables between the T-CON and the LCD panel.
There is no 5-blink error code.

Sound:ok
Inverter board:ok


TCON or lcd panel problem?

Any schematic for TCON board with test points?