Trying to Save - SONY BRAVIA KD-75X780F - No Picture BUT there’s sound

[Diah]

Also check the resistance relative to gnd t-con of these points (CKV1- 6 (there are 12 points in total)) with the panel connected (two cables connected), then with one cable disconnected and with the second cable disconnected.

lotas we approved the FRC on MB didn't start at all.. PIQ it did,,,, both circuit are at same SoC.. temperature he report normal noover load... PMIC he didn't report the test points i asked... but i was little sure they are fine,,

he had likely deep sleep on Android MB. , USB stick no more than 4Gb in MBR mode fat 32 formatted and the last firmware from Sony download extract it to ave one file name to copy on the stick... while the stick in USB 2 black on the side, do hard reset to change the front lrf from white to green.... you may also plug in air mouse at other USB port to make load on firmware to load complete

[KYBOSH]

Very strange no one can see the thumbnails in post #73...

where are the reset of yours measurements off the 5 points i asked?

nothings here or there dont make it complex other wise i will never ask

So sorry... im not sure why you cant see the pic but let me post the readings plainly here:
WP = 3.3V
FAULT_H2 = 0.0V
SEQ = 0.0V
PRC = 3.3V
RST = 3.3V

but the other two points?

FB_VRD = 0.0V
VRD = 0.0V
VSS 7.6 = 0.1V
VOFFE_-11 = 0.1V

[lotas]

I forgot to clarify, did you try connecting the dots (put a jumper between FB331 and FB332 and disconnect the left and right cables from the panel in turn?

[KYBOSH]

I forgot to clarify, did you try connecting the dots (put a jumper between FB331 and FB332 and disconnect the left and right cables from the panel in turn?

Apologies... I did not get a chance to do this one thing while I had the jumpers on.
I can go back and perform this test now if its still relevant.

Shall I take the readings of CKV1-6 before or after I do the jumper test?

Also I have a question about those test points. Why are there 2 right next to each other? They seem to be on the same trace so why 2?

[lotas]

Yes, install a thin wire jumper first and check this test.We will talk about the CKV1-6 readings later, after the test with the jumper.
Disconnect the cable from the T-CON side, that is, install a jumper and disconnect the left cable from the T-CON and turn on the TV and see the image appears on the right side, if not, turn off the TV and connect back the left cable and disconnect the right one and also check the image from left side.

[KYBOSH]

Yes, install a thin wire jumper first and check this test.We will talk about the CKV1-6 readings later, after the test with the jumper.
Disconnect the cable from the T-CON side, that is, install a jumper and disconnect the left cable from the T-CON and turn on the TV and see the image appears on the right side, if not, turn off the TV and connect back the left cable and disconnect the right one and also check the image from left side.

Im at the set right now but i just want to clarify for this experiment.... you mean the LVDS cable (from the mainboard) or the FCC to the display?

Edit: i reread a previous post you made about this. You said to disconnect cable from panel.
Results coming shortly.

Edit2: test complete lotas and no change in display. I jumped 331 and 332 and powered on with both FCCs to panel connected. Then i tried with just the right FCC connected (after powering off and back on again), then i repeated for the left. Im curious why this would have worked as both 331 and 332 have the same voltage across them (3.3v)?

[Davi.p]

Can you check in continuity mode if there is a corresponding pin for both FB_VRD and VRD in the other connector? and also eventually their voltage (all connected)?

Check also if on the VRD line there is somewhere connected a very small cap, that is probably near the ICD1 chip, if this is the case, one can think to jumper VRD----FB_VRD and see what happens..

When you checked VRD voltage was hooked or unhooked of panel? One can think that FB332 makes a loop to VRD through panel board, then feeds also VRD line through panel and returns to FB_VRD.. so one can check this..

[Diah]

So sorry... im not sure why you cant see the pic but let me post the readings plainly here:
WP = 3.3V
FAULT_H2 = 0.0V
SEQ = 0.0V
PRC = 3.3V
RST = 3.3V

yours PMIC supply V as it should, i suggest you stop doing any experiment of jumper etc. its all unknown and no document around here

the think you can do take out the bezel and inspect again and again all the glass, under it there will be Gold Foil transfer the VCC. if it some where broken the screen will remain black.

if every things fine..try to wake up the mainboards , by USB Firmware ( air mouse ) and the process of hard reset by joystick.

[Davi.p]

Almost nothing is documented in todays tv sets.. so do it as you feel Kybosh bye...

[Diah]

there are no SW switch signal coming from MB.. so the t-CON and its slave Panel like dead. when there are signal then all points at the ribbon sockets will be active.. right now ZERO. so why i go to destroying circuit which its not active !!!

Oscillator on the LVDS socket at MB will show no activity for FRC at all.

[KYBOSH]

Good morning everyone!

Can you check in continuity mode if there is a corresponding pin for both FB_VRD and VRD in the other connector? and also eventually their voltage (all connected)?
Check also if on the VRD line there is somewhere connected a very small cap, that is probably near the ICD1 chip, if this is the case, one can think to jumper VRD----FB_VRD and see what happens..
When you checked VRD voltage was hooked or unhooked of panel? One can think that FB332 makes a loop to VRD through panel board, then feeds also VRD line through panel and returns to FB_VRD.. so one can check this..

I just checked for continuity of FB_VRD by running the other test lead across the all pins of both connectors and this is what I found.


When both FFCs are connected the resistance between the Right connector and the Left connector is 56Ω for FB_VRD and 0Ω (shorted) for VRD.
When the Left FFC is removed (leaving the Right FFC on) the resistance between the Right connector and the Left connector is 60Ω for FB_VRD and 0Ω (shorted) for VRD.
When the Right FFC is removed (leaving the Left FFC on) the resistance between the Right connector and the Left connector is OPEN for FB_VRD and 0Ω (shorted) for VRD.
When both the Right and Left FFC is removed the resistance between the Right connector and the Left connector is OPEN for FB_VRD and 0Ω (shorted) for VRD.

As I dont understand the VRD I dont know how to interpret these findings but I find the difference on resistance of 1 FCC being off vs the other as very strange.

Also I checked the voltages of VRD and FB_VRD yesterday and their voltages were 0.0V with all cables connected.
I do not see how the FB_VRD trace leads to the ICD1 chip but I will keep looking and probing to figure it out.

there are no SW switch signal coming from MB.. so the t-CON and its slave Panel like dead. when there are signal then all points at the ribbon sockets will be active.. right now ZERO. Oscillator on the LVDS socket at MB will show no activity for FRC at all.

I dont have a functioning o-scope unfortunately but a software reset sounds like a good idea. If anything it will eliminate that as a possibility and it has little to no risk in it.

If/when we run out of easy ideas I'll have to take your advice and look over the panel and panel board again.

[Davi.p]

1) how do you found the corrispondence between two FB_VRD if they have 56ohm between? Does your tester beeps at 56ohm? What i thought is that FB_VRD had to be probably two separated lines because they controls the integrity of each gate drivers column (??), but if they where separate signal they might have a different indication mark and test point... i don't know..
2) You said the tv had been previously opened, well we know often bad tv sellers can lie or hide something, they can have made repair attempts of various gender, they can have reflowed tcon main chips like i did on mine and ruined the card, on mine for example, after the bad managed reflow i have no more video and also the feedback circuit now marks always 0v, my guess is that feedback circuit starts the signal on the main chip (FPGA/CPLD), travels through the panel and goes back to tcon, charging a very small cap (timing cap) and entering the pmic (you have two main chips and 2 pmic)

3) i also thought that FB331/2 might be a return signal, the signal sender could be a common VCC 3,3v and are a separate feedback respect the VRD loop
--------
Conclusion, my guess you have bad tcon, as always i recommend to buy one from a said working set/cracked panel.. i known there are many tricky seller out there and they can lie like a jail man.. good luck

[KYBOSH]

1) how do you found the corrispondence between two FB_VRD if they have 56ohm between? Does your tester beeps at 56ohm? What i thought is that FB_VRD had to be probably two separated lines because they controls the integrity of each gate drivers column (??), but if they where separate signal they might have a different indication mark and test point... i don't know..
2) You said the tv had been previously opened, well we know often bad tv sellers can lie or hide something, they can have made repair attempts of various gender, they can have reflowed tcon main chips like i did on mine and ruined the card, on mine for example, after the bad managed reflow i have no more video and also the feedback circuit now marks always 0v, my guess is that feedback circuit starts the signal on the main chip (FPGA/CPLD), travels through the panel and goes back to tcon, charging a very small cap (timing cap) and entering the pmic (you have two main chips and 2 pmic)

3) i also thought that FB331/2 might be a return signal, the signal sender could be a common VCC 3,3v and are a separate feedback respect the VRD loop
--------
Conclusion, my guess you have bad tcon, as always i recommend to buy one from a said working set/cracked panel.. i known there are many tricky seller out there and they can lie like a jail man.. good luck

1. YES! My MM will beep almost immediately at 56Ω. Sometimes it will take a second or two but the reading is steady at 56ohms.
2. YES! The TV was previously opened but I cant tell if any of the components were touched or taken off. If I recall the tape holding most of the wires were still on the chassis and undisturbed so I honestly dont thing the previous owner went far in their diagnosis. Certainly dont think they swapped out parts/boards.

I will look into getting a replacement T-Con board for this TV and see what happens. I dont see any from a reputable seller which I can be certain is new or at the very least confirmed functional. This is very important as we need certainty moving forward.

[admxxx]

Hi all, I have the same exact model with the same exact issue! Was there any progress? Does the software reloading made any changes?
I ordered a working t-con from Aliexpress and install it , still the same! I also che led the voltage on Vone on the t-con and there's no voltage , I checked the output on the traces from M silver color chip before the tint capacitors and there's 0.98v or 0.05v alternating among the capacitors. But after the capacitors there's no actual voltages! Wish my tests could help figuring out the issue for me or Diah

[Diah]

Hi all, I have the same exact model with the same exact issue! Was there any progress? Does the software reloading made any changes?
I ordered a working t-con from Aliexpress and install it , still the same! I also che led the voltage on Vone on the t-con and there's no voltage , I checked the output on the traces from M silver color chip before the tint capacitors and there's 0.98v or 0.05v alternating among the capacitors. But after the capacitors there's no actual voltages! Wish my tests could help figuring out the issue for me or Diah

i didnt catch yours test.. but its interesting if you have same model and same fault... so please open new Threat and post photos of yours MB and the test you are mentioned , so i can understand more what are you talking about .

[admxxx]

Thanks Diah for the reply. I managed to get picture and the TV is working now, I blocked pin number 13 on the the right side flex cable that feed the COF from the T-con, I first blocked all timing pins then narrow down to one pin. The TV is working but there's a faint horizontal lines on all right side of the TV that not very visible, add to that there's one strip of horizontal line that visible according to what viewing on the screen.

[Davi.p]

..

[Diah]

Thanks Diah for the reply. I managed to get picture and the TV is working now, I blocked pin number 13 on the the right side flex cable that feed the COF from the T-con, I first blocked all timing pins then narrow down to one pin. The TV is working but there's a faint horizontal lines on all right side of the TV that not very visible, add to that there's one strip of horizontal line that visible according to what viewing on the screen.

sorry Man, i will take yours Post as unrealistic, this will not happen to let FRC cut off Signal. pass thru -- .. or the T-CON go to sleep mode,, as its generated with 2 SPI independent one. ,
yes it could be happen if Panel VCC broken on under layer glass of the panel... more i cant say unless the whole boards and the display picture to see... cut off FRC we did approved in this threat... but the reason to me still unknown. sorry

[admxxx]

It's little bit harsh man! I'm sharing my success so others can benefit from it! By the way that line I blocked is CKV2, I am trying to find what does shorted to and try to kill the short with a 110v ac in serial with an old tungsten lamp. Im not happy about the white strip that's on the LCD screen. By the way, this TCON won't work unless both flex cable feeding to the COF boards connected! There must be a feedback jumper that I can't find on the tcon board.

[admxxx]

Here're more pictures with a full screen on dark and bright and a close up to show the horizontal lines.