Sony Bravia KDL-40EX400 Dead totally

[CraigR]

Re: Sony Bravia KDL-40EX400 Dead totally

I was just stating that when I was trying to get the backlights to come on the main board and TCON were both disconnected and the backlights only flashed on for less than a second and my understanding is that they should have stayed on eliminating any possible problem with the power board. Anyway I just tried it again with the TCON disconnected and still get the same readings. so I'm thinking there is still a problem with the power board or inverter or a bulb??

[budm]

Re: Sony Bravia KDL-40EX400 Dead totally

OK, I understand what you mean, so yes the backlights and the PFC Voltage should stay on.
There is thermal sensing circuit that will shut down the PS_ON incoming signal, it is done by SENSOR TH6401, q6402, D6405 the sensing circuit will send the signal to the latch circuit Q6202, Q6203 to kill the PS_ON signal from reaching MOSFET Q6201.
You can ground the Anode side of D6405 to the secondary side ground to kill the thermal sensing signal to see if the backlights and the PFC Voltage will stay on or not.
See the diagram for more details.

[CraigR]

Re: Sony Bravia KDL-40EX400 Dead totally

here is D6405 I can't tell what side is what can you?

[budm]

Re: Sony Bravia KDL-40EX400 Dead totally

See that thin bar on the body (lower part of the body looking at the picture)? That is the Cathode. You can verify by using the Diode mode on your meter.

[CraigR]

Re: Sony Bravia KDL-40EX400 Dead totally

Use a meter duh I'm a little slow today I guess. Ok I will solder on a little wire to the other end and ground.

[CraigR]

Re: Sony Bravia KDL-40EX400 Dead totally

Ok, no joy there. Does the same thing. With main board disconnected then the harness shorted to check backlights again it just flashes on for a second when plugged in. Same as post #1

[budm]

Re: Sony Bravia KDL-40EX400 Dead totally

OK, let verify that the OPTO PH6103 does stay on by checking the DC Voltage between pin 3 and pin 4 when PS_ON (staying HI) is applied.
When the OPTO is turned on by the PS_ON signal, the Voltage on pin 3 and 4 should goes from > 3V to <1V, this LO signal is fed into the IC6301 (CXA3809, very complex IC) pin 2 (MODE) which is the combo IC for the PFC and the 12V/24V SMPS.
https://www.badcaps.net/forum/search...archid=4091883

[CraigR]

Re: Sony Bravia KDL-40EX400 Dead totally

Ok, if I did this correct the the center one and between the top 2 pins it's 1.57v and does not change with power button.

[budm]

Re: Sony Bravia KDL-40EX400 Dead totally

OK, you can do the test using the resistors for the PS_ON and the BL_ON just to verify if the backlights will stay on without having the main board connected.
At this point it looks like you do have main board problem dues to no toggle of the Voltage on pin 3 & 4.
So lets see if we can make the backlights stay on and the PFC to stay on first by using force on method.
BTW, they the two pins on the bottom, the top two pins are for the LED inside the OTPO.

[CraigR]

Re: Sony Bravia KDL-40EX400 Dead totally

That's what I did in my first post. Lights come on for less than a second when plugged in. Then I need to wait a bit before it will do it again like a cap needs to discharge first or something.

[CraigR]

Re: Sony Bravia KDL-40EX400 Dead totally

Guessing you gave up budm?

[budm]

Re: Sony Bravia KDL-40EX400 Dead totally

This is a complex problem because you are having two problems with two board: the main board not toggle the PS_ON and not producing any error codes, the power supply board that sense error some where so it goes into latched shutdown.
I will really have to study the circuit in depth which is not going to be easy since the function of that IC CXA3809 is complex.
I am hoping that some will have the same model and check the Voltages for us.

[tibimakai]

Re: Sony Bravia KDL-40EX400 Dead totally

I believe, that they sell a kit with that CX IC.

[budm]

Re: Sony Bravia KDL-40EX400 Dead totally

@tibimakai: I saw that kit some where too. Didn't you have the problem with this same model that I helped you out with before? I believe yours had error codes, this one has nothing, and some people was able to fix it by reloading the firmware.

[CraigR]

Re: Sony Bravia KDL-40EX400 Dead totally

I put that kit in before posting this and it did not help. Anyway I ordered another power board and that did fix it so no problems with the main board. HOWEVER when I turned the set over to look at the picture the screen was cracked so scrap another one out and sell the parts I guess. Thank you all for the help especially budm many thanks!

[budm]

Re: Sony Bravia KDL-40EX400 Dead totally

Thanks for the follow-up.

[Shinju]

Re: Sony Bravia KDL-40EX400 Dead totally

Small LED flashlight or if you have a smart phone with flashlight app will save you a lot of time on checking for cracked screens. I see you have bought a few that ended up being cracked. I have dodged quite a few cracked screens now.

I had that happened a couple of times and now I check every LED/LCD and plasma before I take em home.

[tom66]

Re: Sony Bravia KDL-40EX400 Dead totally

Yep, had one or two like that, flashlight really helps. Some LCDs it can be really hard to tell though.

[gamethriller]

Re: Sony Bravia KDL-40EX400 Dead totally

If you have a good powerboard ill buy it.