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Old 12-09-2017, 02:41 AM   #21
freakaftr8
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Default Re: Sony XBR75X850C no picture backlights on

That is my next step. I'm thinking I'm going to give another tcon a go first sense I don't know if this one I ordered was damaged in the same fashion as my original.
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Old 12-09-2017, 04:12 AM   #22
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Default Re: Sony XBR75X850C no picture backlights on

FRC board?? Why? which board you mean for FRC please..?
"One capacitor was shorted like I mentioned previously" i don't have noticed, have you replaced it? It's on the panel's board?
For the value that have my little opinion, it's better to troubleshoot the original tcon and to order also the faulty chips togheter with the new tcon, so if another tcon fails, you can work now to replace components as i suspect when theese fault happens people carries tv to service center and they tells to they that panel is fault so some people sells the boards as good.

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Old 12-09-2017, 01:40 PM   #23
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Default Re: Sony XBR75X850C no picture backlights on

FRC board meaning the top boards that run across the panel that had the ribbon cable drivers fused to them. I took your advice and supplied 12v to HAVDD line and got vertical flickering lines both sides.

Yes one of the panel boards had it shorted capacitor which I already replaced now I have no short reading across HAVDD

Good news is nothing shorted out.

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Old 12-10-2017, 09:30 AM   #24
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Default Re: Sony XBR75X850C no picture backlights on

12v applied to HVDD line. Both side get these flashing lines but nothing shorted out this is only 12v not required 16v to this input. But this was just a test to make sure that the panel board that I repaired doesn't short again
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Old 12-10-2017, 09:50 AM   #25
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Default Re: Sony XBR75X850C no picture backlights on

Well, i don't have said this,i've said to supply HAVDD or AVDD (i don't know which, you have the board..) with that voltage but with panel disconnected to anything else, so there was no risk of bad returns, anyway lets hope no more damages; FRC stands for Frame Rate Conversion and is not the long panel's board, is another board.
So.. finally with all hooked up do you have all the voltages? AVDD, VGH, VGL, VCOM, VCC, V1D2, V3D3, VGMA1-22?
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Old 12-10-2017, 09:57 AM   #26
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Default Re: Sony XBR75X850C no picture backlights on

No I do not have any of those voltages. The tcon is only producing 1.1v to the tcon processor core only.

This is why I was wondering is this tcon does not produce voltages unless the panel is connected.
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Old 12-10-2017, 09:58 AM   #27
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Default Re: Sony XBR75X850C no picture backlights on

But i have said "with all hooked up"... so still no voltages?
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Old 12-10-2017, 09:59 AM   #28
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Default Re: Sony XBR75X850C no picture backlights on

Actually I have 1.3v to panel but all other voltages missing.
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Old 12-10-2017, 10:00 AM   #29
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Default Re: Sony XBR75X850C no picture backlights on

And yes this is completely hooked up.
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Old 12-10-2017, 10:07 AM   #30
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Default Re: Sony XBR75X850C no picture backlights on

I don't want to annoying you but it's not the time to test something on tcon board? If you don't pubblish any good tcon picture i can't help you..
You can test voltages and discrete semiconductors.

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Old 01-16-2018, 08:36 PM   #31
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Default Re: Sony XBR75X850C no picture backlights on

Ok. New tcon received. Before I even connected the panel to the T con I tested for voltages and as expected I have 12v and with LVDS cables connected but no voltages to the outputs. Oddly it didn't even throw the green Amber needing firmware update this time. And with panel connected still no voltages.
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Old 01-17-2018, 04:52 AM   #32
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Default Re: Sony XBR75X850C no picture backlights on

evidently there's a short on the panel, if i would be you i would d.l. the pwm generator chip datasheet and study it.
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Old 01-17-2018, 10:12 AM   #33
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Default Re: Sony XBR75X850C no picture backlights on

While there could be, however, I'm not getting any voltage even without the panel connected. Is it possible that some of these Samsung/Sony S LCD tcon boards Do not power up the PWM or regulators unless it sees a panel connected?
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Old 01-17-2018, 12:18 PM   #34
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Default Re: Sony XBR75X850C no picture backlights on

Whitout to read again all posts i remember that you already tested this, when you do not connect panel there's no power funcionalities, i can't know how are all the designs, it's better for you that you download this datasheet, tell to us the chip marking also and the tcon model or a good sunlight picture..
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Old 01-17-2018, 12:22 PM   #35
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Default Re: Sony XBR75X850C no picture backlights on

On the 1st original board if I heated up the voltage regulator IC With the right half of the panel this connected I saw the left hand side come up. Of course this is before I saw the shorted M LCC capacitor on the source driver board. Leaving that side disconnected still does not produce an image on the left. I should note that the 2nd replacement tcon board I got from the same company was missing in M LCC capacitor on the tcon that I swapped over from another one. I have a feeling I'm getting bad boards from this company
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Old 01-17-2018, 12:24 PM   #36
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Default Re: Sony XBR75X850C no picture backlights on

And also as soon as I found the missing M LCC after replacement I suddenly got the Orange green firmware update warning on the TV again and I went ahead and updated the firmware again which displays no image.

I think my next step would be to track out the configurations of these voltage regulators can find out why they're not outputting when they're getting 5 v on the VCC
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Old 01-17-2018, 12:46 PM   #37
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Default Re: Sony XBR75X850C no picture backlights on

This is the regulator in question, there are two of them.

Of course, no information on the internet about them.
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Old 01-17-2018, 05:08 PM   #38
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Default Re: Sony XBR75X850C no picture backlights on

That IC is from a fu**ing Chinese brand "SiliconMitus" whose site don't give any info on the products, if you want to contact them and say you're hobbyst repairer, at maximum you *称@ them!
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Old 01-17-2018, 06:23 PM   #39
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Default Re: Sony XBR75X850C no picture backlights on

Lol I'm exchanging the board. Again.
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Old 01-20-2018, 02:45 PM   #40
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Default Re: Sony XBR75X850C no picture backlights on

OK new board this time applied 12 V on T con and connected LVDS cables only did not connect panel to outputs. DVM on output inductors ready.

Power up and no voltage anywhere except for 1.1 to CPU core and some sporadic 12v around caps only.

Absolutely no regulation going on anywhere except for that. So I can confirm the panel is not the problem.

Is it possible that the main board is not sending a turn on command via LVDS? I don't have schematics for this board or schematics for the main board or know the pin out configuration of the LVDS cables.

There is absolutely no information on the Internet for this particular model including part diagrams and schematics.
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