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Old 01-24-2018, 10:37 PM   #81
freakaftr8
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Default Re: Sony XBR75X850C no picture backlights on

Interesting. LVDS cable pin 3 on mainboard to 39 on tcon labeled Panel ON. This is the smaller 41 pin connector.

Edit: I tried grounding this pin and error pin also and also applied 5v. No change.
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Did I leave the soldering iron on?

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Old 01-26-2018, 04:43 PM   #82
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Default Re: Sony XBR75X850C no picture backlights on

Here is the panel with 12v applied to the HVDD. So now I know I'm getting somewhere with my persistence. Lol.
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Old 01-26-2018, 08:09 PM   #83
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Default Re: Sony XBR75X850C no picture backlights on

Alright. I'm officially stumped guys. The Samsung derivative tcon that I got I thought worked noes not put out voltages. This particular tcon board pushes the same exact panel as the Sony.

I applied 12v to it and there is a actual 8 pin regulator that does not energize so there is no voltage at all including the 1.3 to the core. I jumped the regulator and now have core voltage and some sporadic 3.3 and 5 V but absolutely nothing running off any of the regulators for the same voltages that I missing on the Sony board.
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Old 01-26-2018, 09:14 PM   #84
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Default Re: Sony XBR75X850C no picture backlights on

Something has got to be either shutting down these regulators or possibly something needs to energize them or be a switch. What do you think
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Old 01-27-2018, 05:39 AM   #85
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Default Re: Sony XBR75X850C no picture backlights on

What about my post #77?
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Old 01-27-2018, 06:47 AM   #86
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Default Re: Sony XBR75X850C no picture backlights on

Have you tried shorting CS30 on the right? Right there there are some 0ohm res., have you tested them?
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Old 01-27-2018, 09:34 AM   #87
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Default Re: Sony XBR75X850C no picture backlights on

Yes I tried CS30, One side of that capacitor has 5v coming in I tried shorting I tried powering up with it shorted nothing makes a difference
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Old 01-27-2018, 09:36 AM   #88
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Default Re: Sony XBR75X850C no picture backlights on

I have a scope. The voltages do jump about .02v when 12v is applied.
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Old 01-27-2018, 09:48 AM   #89
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Default Re: Sony XBR75X850C no picture backlights on

It seems a missing enable signal, at least from the low of my knowledge..
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Old 01-27-2018, 03:27 PM   #90
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Default Re: Sony XBR75X850C no picture backlights on

IT does to me too. But even with schematics, I donyt see where that would be coming from.

Given how many tcons I've tried, I'm really starting to think this turn on signal comes from the mainboard.

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Old 01-27-2018, 03:45 PM   #91
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Default Re: Sony XBR75X850C no picture backlights on

I'm starting g to think that this area the the PWM generator. The c oil is VCC 1.15v and there's 6v and 4.4v and 3.3v around that IC.
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Old 01-27-2018, 05:00 PM   #92
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Default Re: Sony XBR75X850C no picture backlights on

What?? I'm curious, what you have fed to the tcon to see image?
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Old 01-27-2018, 05:15 PM   #93
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Default Re: Sony XBR75X850C no picture backlights on

These areas
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Old 01-27-2018, 05:47 PM   #94
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Default Re: Sony XBR75X850C no picture backlights on

Sorry, i have understood nothing on post #91...
The PWM ic on the photo post#91 RT6932 is by Richtek, Samsung uses them often on LED TVs, on it's website unfortuantely there's no d.sheet for this, but i'm watching an interesting one of the series, found by "RT69" search term, this:
http://www.richtek.com/assets/produc.../DS6908-01.pdf
As you can see some of theese chips are fu**ing programmable ones so there's a nvm memory inside that stores settings, it's very hard usually to rebuild a lost programming of them, one has to write a program to use with a i2c interface and send the data to it, but you also lack of the data. Sometimes i2c lines are affected by bad mlcc caps on them, so on the tcon or on the mainboard is better to find the i2c line that goes to the 3 chips with missing tensions and replace the caps you find on the line/s, usually by only removing them the line return to work again.

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Old 01-27-2018, 06:15 PM   #95
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Default Re: Sony XBR75X850C no picture backlights on

Correction: the chip linked is a all in one solution and so it has a memory inside but in your tcon there are 4 chips for the ps section so i think it's difficult them have i2c, watching that d.s. i see that a typical power sequence is VGH>VGL>AVDD, so it's possible every chip communicate to each other by a Powergood signal, let's suppose that one of the 2 VGH-VGL chips are bad, the sequence is interrupted, i would start to search a new tcon (and claim refund for the ones you got) or search a single pin that joins the chips, taking consideration of GND and VCC signals.
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Old 01-27-2018, 06:38 PM   #96
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Default Re: Sony XBR75X850C no picture backlights on

Each IC is receiving VCC 5v and there is some 3.3 and 12v there too.


Too bad there are no schematic diagrams of these I c's in question. The Samsung tcon for the un75ju641df uses same ICs and it also will not power up.

I am so close but still stuck

Is the RT6932 the main PWM for all regulation ICs? It's always powered and putting put voltages.

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Old 02-02-2018, 02:06 PM   #97
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Default Re: Sony XBR75X850C no picture backlights on

Back to what you were saying the SDA and SCL of all of these ICs communicate with each other and if one is not happy they all shutdown? Is that correct? Why do I have 1.15 v then? That ic generates 1.15, 1.1 3.3 and 5v. All those seem to work.
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Old 02-02-2018, 05:58 PM   #98
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Default Re: Sony XBR75X850C no picture backlights on

I don't think all the chips have a serial comm line, but how knows? If you dont find the usual voltage divider connected to the outputs and an input the chip is programmable and have a ser. comm.
I think that the chips are in a chain, the output voltages must appear in a sequence, when a chip is failing all its voltages doesn't appear, the acknowledgement for the next chip in the sequence is not activated so you lack also of all subsequent voltages, so i have said to you maybe i remember, the voltage sequences for a certain all in one so called "PMIC" chip, search back in the posts.

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Old 03-09-2018, 01:12 AM   #99
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Default Re: Sony XBR75X850C no picture backlights on

FIXED!!! I decided to have another go at this TV before it met the recycle bin, (spring cleanup around the house) and apparently the MLCC capacitor that I replaced on the panel board was not making a good enough connection I resoldered it again and perfect picture!!

So all parties at were intrested, this particular T con board will not allow any power through the tcon board to the panel unless there are no shorts or "no opens" within the panel driver board MLCC capacitors!! Wierd setup!! I had never seen a TCON not attempt to output voltages if not connected to the panel but maybe I'm wrong. The side that had this shorted M LCC had the panel ID IC on it, So even though I was pretty sure the replaced M LCC capacitor was good it obviously was not. That's a 3 month problem finally solved. Now trying to put it back together is the interesting part..
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Old 03-09-2018, 04:07 AM   #100
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