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Old 01-20-2018, 02:26 PM   #41
Davi.p
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Default Re: Sony XBR75X850C no picture backlights on

Tell me the panel model number so i search the datasheet.
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Old 01-20-2018, 02:30 PM   #42
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Default Re: Sony XBR75X850C no picture backlights on

Model name S750qf59 v0
Model nunber 96.75S02.201
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Did I leave the soldering iron on?
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Old 01-20-2018, 02:33 PM   #43
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Default Re: Sony XBR75X850C no picture backlights on

Have you ever connected antenna so you can hear channels sound, or another input type?
The model you write is not correct i think, i find no entries in the search... possible?

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Old 01-20-2018, 06:24 PM   #44
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Default Re: Sony XBR75X850C no picture backlights on

Yes has perfect sound I can hear sounds of menus and options when I press them also I hooked up HDMI through my chromecast in heard a video playing.

Also remember a while back when I was on my original Tcon, I had half the panel showing I when I heated up one of the voltage regulators. This is when I found the shorted MLCC on the panel board which has been replaced . At that time I only had one side connected but I could not reproduce it after a little while with heat.
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Old 01-20-2018, 09:40 PM   #45
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Default Re: Sony XBR75X850C no picture backlights on

Ok no power here. Is the ICD1 on the right the master voltage regulator? It's dead. I can touch pin 3 to 2 on ICA1 or ICB1 and get roughly either 6.5 or 10.4v depending on which one I cross together. This is essentially bridging the path to the ICD3 to achieve 10.4v at AVDD.

ICD4 also dead.
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File Type: jpg 20180120_203848.jpg (535.7 KB, 10 views)

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Old 01-20-2018, 09:45 PM   #46
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Default Re: Sony XBR75X850C no picture backlights on

I do have voltage here at all times at ICD2 for the 1.15 VCC
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Old 01-20-2018, 09:50 PM   #47
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Default Re: Sony XBR75X850C no picture backlights on

Also On my original board I did not have any voltages either but when I heated up ICD3 suddenly everything came up but it only happened a few times and I had a picture
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Old 01-21-2018, 01:09 AM   #48
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Default Re: Sony XBR75X850C no picture backlights on

I suppose ICD1 could be the dc converter and gamma all in one. I've heard of this before.
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Old 01-21-2018, 02:59 AM   #49
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Default Re: Sony XBR75X850C no picture backlights on

Ok confirmed voltages are not turning on. Like I said before bridging ICA1 or ICB1 will generate a crosshatch flickering pattern because of crosstalk feedback and not a filtered DC bus to the AVDD, only supplying 10v to AVDD this way, where it need a a minimum of 16v I can see an image!

So DC regulators are for certain not being turned on. Why?

5 tcons later and same thing!

Is this the mainboard that has tok do the switching? Of course with this hack I still have no VCOM, VREF, or VGH, so it's not right however looks like the panel is trying to work.
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Old 01-21-2018, 07:15 AM   #50
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Default Re: Sony XBR75X850C no picture backlights on

Sorry it's difficult for me, bad pictures, some terms i can't translate... the lack of testpoints.. Need better pictures but anyway without pwm generators datasheet are steps in the dark.. So you say that on ICD1,3,4 you have no 12v? On the last photo CL25 and CL20 which tension has?

Last edited by Davi.p; 01-21-2018 at 07:18 AM..
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Old 01-21-2018, 10:47 AM   #51
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Default Re: Sony XBR75X850C no picture backlights on

On ICD1, 3 and 4, I've 5v VCC. On CL20 and CL25, 1.8v.
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Old 01-21-2018, 01:25 PM   #52
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Default Re: Sony XBR75X850C no picture backlights on

Obviously these 3 regulators are receiving VCC. But trying to find the turn on command pin... Have no idea
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Old 01-21-2018, 07:33 PM   #53
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Default Re: Sony XBR75X850C no picture backlights on

Here's what I get bridging ICA1 or ICB1
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Old 01-22-2018, 12:41 AM   #54
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Default Re: Sony XBR75X850C no picture backlights on

Ok I backfed a 16v line into AVDD from another tcon. Found that the AVDD runs into CS29 here. Also ICD3 and ICD4 ARE receiving 12v also normally along with 5V on VCC.

I also noticed 16v at CG8 of ICD3. Because I'm backfeeding the 16v at AVDD from other tcon..

ICD4 thou, seems unaffected as i believe that IC drives VOFF and others it seems.

Still no voltage at HAVDD. This would be at point DSB1.. DSA1 is alive with the 16v from the feed off the other tcon.

Now in pretty sure that IF I was able to plug all the missing voltages as long as I knew the correct voltages for the panel operation, to the tcon, I bet I would have a perfect picture.

This is a major hack though, I'd like to know why I've managed to try 4 different tcons now all with the same result. Like I said earlier, I supplied 10v to AVDD and saw a jumpy misconstrued picture with the Sony menu screen and avaliable inputs.

So this leaves me to trying to determine exactly why the regulators are not switching on.
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File Type: jpg 20180121_233546.jpg (754.3 KB, 15 views)

Last edited by freakaftr8; 01-22-2018 at 01:09 AM..
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Old 01-22-2018, 09:14 AM   #55
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Default Re: Sony XBR75X850C no picture backlights on

Hey wait a moment! From the last picture i see the burnt mark on ICB1, is that mark made by your shorting sparks? Almost surely them are single mosfets even if them are called "IC" but the burnt is between gate and drain! Not good...
Quote:
Also ICD3 and ICD4 ARE receiving 12v also normally along with 5V on VCC.
You don't know if that 5v is VCC or not, it can be a VREF, an internal LDO...
Quote:
Like I said earlier, I supplied 10v to AVDD and saw a jumpy misconstrued picture with the Sony menu screen and avaliable inputs.
Where is this screen? You don't have taken picture...
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Old 01-22-2018, 10:59 AM   #56
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Default Re: Sony XBR75X850C no picture backlights on

Those are not burn marks, I touched up the solder pads what you're seeing is flux.

As for the picture, I'll try to take one again tonight but I need to feed more than 10 V into HVDD as it is just not enough to produce stable image

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Old 01-22-2018, 12:06 PM   #57
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Default Re: Sony XBR75X850C no picture backlights on

No i don't think, HVDD=Half VDD=15 or 16 /2= 7,5 - 8 v.
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Old 01-22-2018, 12:53 PM   #58
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Default Re: Sony XBR75X850C no picture backlights on

Right, well injecting 16v to AVDD, I do not get a half voltage regulation to to the circuit being dead. I could inject 8v at HAVDD and see what kind of a image I have however I still will not have any VOFF, VREF, VGHor VCOM.
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Old 01-22-2018, 01:24 PM   #59
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Default Re: Sony XBR75X850C no picture backlights on

No is wasted time without VOFF-VON!
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Old 01-22-2018, 04:35 PM   #60
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Default Re: Sony XBR75X850C no picture backlights on

How would one succeffuly force the PWM circuit on in this instance?
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