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

[KYBOSH]

The inner connector test points are tied together on the tcon board so you have to always measure 0ohm from 1 to the other.. when both FFC are connected you have to read 0ohm every measure combination.. so i guess you have faulty FFC ribbons or faulty multimeter cables.. if you have FFC in to the side of FB_1 then FB_1--> FB331 must check 0hm.. similar the other connector..

PS: check very often multimeter crossed probes in ohm, a good DMM and good cables must check around 0,1-0,0 ohms, post a picture of you meter, if you didn't already..

I have updated the measurements table (see above) and I am not getting ANY continuity with any combination of testpoints or FCCs on/off.
Here is a picture of my MM and how it reads when my leads are touching.

[Davi.p]

some measurements are out of logic..

[lotas]

	Both FCCs On	Right FCC Off Only	Left FCC Off Only	Both FCCs Off
FB_VRB + FB_332	2MΩ↑	51.3KΩ	4.18KΩ	2.4MΩ
FB_1 + FB_331	6.13KΩ	11.81KΩ	2.58KΩ	3.1MΩ
FB_331 + FB_332	14.4Ω	5.6kΩ	5.6kΩ	9.5kΩ
FB_1 + FB-VRB	2MΩ↑	2MΩ↑	2MΩ↑	13MΩ↑

Note: This is with the TV off, disconnected from the mains and both LVDS cables connected (if this makes a difference).

Try installing a jumper between FB 332 - FB 331 and then check by disconnecting the left cable, then the right cable...

[KYBOSH]

Try installing a jumper between FB 332 - FB 331 and then check by disconnecting the left cable, then the right cable...

Okay!
To clarify... you wish for me to solder a small wire unto test points FB_332 & FB_331 and take all the measurements again?

[Davi.p]

yes, but also with both ffc

[lotas]

Okay!
To clarify... you wish for me to solder a small wire unto test points FB_332 & FB_331 and take all the measurements again?

No, what if you turn on the TV and check whether the image appears on some half of the panel.

[KYBOSH]

No, what if you turn on the TV and check whether the image appears on some half of the panel.

Sorry my friend... I didnt understand.
You want me to jumper FB_332 & FB_331 and see if I get an image on the display?

Or are you asking what happens on the display when we disconnected one of the cables?
If this is the question then the result was we still did not get any sort of image.
https://www.badcaps.net/forum/troubl...74#post3511374

[lotas]

Install the jumper and check the same thing with the left cable disconnected and then the same thing (with the right cable disconnected, in turn), and whether the image appears on whichever half of the screen!

[KYBOSH]

yes, but also with both ffc

Here are the resistance values with FB_331 & FB_332 jumpered together.

	Both FCCs On	Right FCC Off Only	Left FCC Off Only	Both FCCs Off
FB_VRB + FB_332	40.4kΩ	2.0MΩ↓	1.0MΩ↑	2.58MΩ
FB_1 + FB_331	6.16kΩ	11.2kΩ	2.97MΩ	2.92MΩ
FB_331 + FB_332	0.2Ω	0.2Ω	0.2Ω	0.2Ω
FB_1 + FB-VRB	2.0MΩ↑	1.0MΩ↑	7.0MΩ↑	6.4MΩ

Note: the resistance of FB_VRB + FB_332 was actually decreasing with the right FCC off and the left FCC on.

[KYBOSH]

Install the jumper and check the same thing with the left cable disconnected and then the same thing (with the right cable disconnected, in turn), and whether the image appears on whichever half of the screen!

Just posted the results of the jumpering.
I will go and turn the TV on with the jumper connected an to see if I have any picture at all.

[Davi.p]

OK i think there is an error in the operation, i'm exiting of the work, i can only check well photos later, i think FB_VRD does not appl at all, i think there is some where a FB_3.. that is the right one..

[Diah]

Diah et al. Any tips on my next step?

Lotas was on the right track to do the test... but i read as usual there are jumping from users to distribution the method.... why ? unknown for me... any way

who want to repair TV he should know how its work and which circuit built in...
at time i wrote no need to attempt standalone test... cause i do know what are going between the circuit as i asked man test... this is not to make me over all but know how as i am proud on my self i do proud on lotas R_J

back to the issue... yours FRC SoC are out from the circuit... this why you didnt have any error code when you disconnect the LVDS..... 12VCC_T-con etc..
BL_ERR can be register as it goes to Main SoC direct--- but all related video will go to FRC SoC then to main SoC... at time FRC SoC out of business... the main SoC will remain work as its not job to monitor this FRC.... he just receive error..... this subject are huge... i just explained in simple way..

OP you will not able to repair it but we can definitely say where are the issue... take out the all heat sinks of MB and post focused high resolution Photo and remark on it any low V you find on the MB... my wish no more distribution

[KYBOSH]

back to the issue... yours FRC SoC are out from the circuit... this why you didnt have any error code when you disconnect the LVDS..... 12VCC_T-con etc..
BL_ERR can be register as it goes to Main SoC direct--- but all related video will go to FRC SoC then to main SoC... at time FRC SoC out of business... the main SoC will remain work as its not job to monitor this FRC.... he just receive error..... this subject are huge... i just explained in simple way..

OP you will not able to repair it but we can definitely say where are the issue... take out the all heat sinks of MB and post focused high resolution Photo and remark on it any low V you find on the MB... my wish no more distribution

Thank you for this insight! As i a still learning would you be kind enough to point out the chips/components you say are bad? I dont know where they are located.

[Davi.p]

Sorry for my last post, was done in hurry.. ok now, have you understood how the feedback circuit is? It's very simple, since i was not able to find another FB test point , the FB_VRD is probably part of it, but i never read this type of acronym, maybe here is different from other sets, maybe this is not passive circuit as usual but is something dialogating with an ic on the panel strip boards, otherwise i think the feeback can be different enough, i can try to interpret, so why VRD? near the FB_VRD there is a VRD signal, does it stays for "Vertical ready"? Is it a simple loop that travels trough the gate drivers sequence? Is it VRD the starting signal and FB_VRD the returning one? Can you check in ohm between them with panel connected and panel disconnected? Then with continuity tester, check between first connector VRD and all second connector pins to find corrispondence, do the same with FB_VRD.. Similarily FB331/FB332 could be a totally different check, they can stay for "3,3v feedback connector 1/2", so connect all the panel, turn on and check voltage on these 2 pins.. but i'm unsure what means 3,3v feedback anyway..

PS: so the old knowledge from Germany is came back, i was sure he came back, and he promptly started polemics against me.. too good to be true he abandoned the site..

[Diah]

Thank you for this insight! As i a still learning would you be kind enough to point out the chips/components you say are bad? I dont know where they are located.

all talking are on mainboards, remove the black heatsink and post photo of the whole area,

[KYBOSH]

all talking are on mainboards, remove the black heatsink and post photo of the whole area,

As requested Sir. Sorry for the wait.

[KYBOSH]

[INDENT]...the FB_VRD is probably part of it, but i never read this type of acronym, maybe here is different from other sets, maybe this is not passive circuit as usual but is something dialogating with an ic on the panel strip boards, otherwise i think the feeback can be different enough, i can try to interpret, so why VRD? near the FB_VRD there is a VRD signal, does it stays for "Vertical ready"?

I searched and the only SONY reference that I could find for VRB is as a reference test voltage for certain chipsets and boards but its noted as V_RB. So this may lend support that this is not a passive circuit but rather an active one with a voltage.

Can you check in ohm between them with panel connected and panel disconnected? Then with continuity tester, check between first connector VRD and all second connector pins to find corrispondence, do the same with FB_VRD..

I have only see one test point marked VRD. Where is the other one you want me to check against?

Similarily FB331/FB332 could be a totally different check, they can stay for "3,3v feedback connector 1/2", so connect all the panel, turn on and check voltage on these 2 pins.. but i'm unsure what means 3,3v feedback anyway..

Im not sure I quite understand the "3,3v feedback connector 1/2" part but once I get the mainboard back in I will take voltage readings of all these FB points and report back.

Thanks again for the input!

[Diah]

so the old knowledge from Germany is came back, i was sure he came back, and he promptly started polemics against me.. too good to be true he abandoned the site..

you AS°°°OL°.. i am here to kill yours mice virus... when the cat is away the mice dance on the table...

As requested Sir. Sorry for the wait.

its useless when some one try to solve issue and you want to follow other... what 3.3V how you will be in the forum to follow to different issze..
any way... just plame your self if you didnt find from me any more response..
yours issue at the is area FRC and iQ circuit... check first all F of FRC & iQ

[KYBOSH]

Its useless when some one try to solve issue and you want to follow other... what 3.3V how you will be in the forum to follow to different issze..
any way... just plame your self if you didnt find from me any more response..

I really respect you guys and have great respect for the forum. As a laymen when someone more knowledgeable than me tries to show me something I am grateful and try in earnest to listen and learn.
I have noticed the animosity between a few of you Legends, Veterans and Hobbyists but I definitely want to stay out of all that. Firstly I dont know how it started. Then I dont know the facts and current events. And lastly I dont know how you guys wish to settle it. For all I know you all will go skiing together in the Alps over the holidays. I hope i do not rub anyone the wrong way by taking suggestions, tip and advice from whoever is good enough to offer it. I see nothing wrong with taking a voltage reading as Davi.p requested as it does not directly relate to or interfere with what you asked me to do (take pictures of the mainboard). If nothing else, its just more data for us to consider, culprits to eliminate and things to learn from. If my thinking is wrong and goes against the Badcaps.net way please let me know. I would love to think this place a safe zone we all come together to learn and fix and have a little fun while we are at it.

yours issue at the is area FRC and iQ circuit... check first all F of FRC & iQ

I am not familiar with these circuits at all but I will study it and try as you intructed. When you say check all F of FRC & iQ.... does F refer to fuses?

Thank you again

[Diah]

requested as it does not directly relate to or interfere with what you asked me to do


I am not familiar with these circuits at all but I will study it and try as you intructed. When you say check all F of FRC & iQ.... does F refer to fuses?

Thank you again

from one point you want to learn... that's fine.... but did you know any attempt to work or fed V at wrong area, you will kill many other parts... so why we do spend.time to help you and we do read how you are going to kill the set ? better leave you and laugh !!! NO this no one serious man man will do it-

you can read on the area i show you F and in general F are fuse .