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

[Diah]

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

please dont take it in wrong way.. we want to know the reason.. thx you posted your success ..
but you have feed back left and right on the T-CON ribbons socket.(( FB_L )). could you messure both while tv working with ref Chassis ?

[KYBOSH]

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.

Wow! Congratulations on the save!
My TV is still on my bench in the same state as I left it in my last post.
I was debating ordering a new T-Con as well but just decided to meditate on it rather than pull the trigger.
Over the last week or two my suspicions grew that I was dealing with a panel issue but to verify I knew i would have to throw working parts at it to eliminate the mainboard and the T-Con.

Amazing that yo you happen to have the same TV with the same issue at the same time and you showed up here!

I know next to nothing about panel troubleshooting and repair. The best I have ever done was the tape off method.

You mentioned you blocked all timing pins.... which ones are those?
You blocked them off then exposed them one at a time until the picture came back? Or how does it work?

Very interested in learning this method.
Please dont think you are insulting me by explaining it as if you were talking to a child... bcos I am completely new to this part.

Thank you in advance for sharing and I look forward to your response.

[admxxx]

If you look at the t-con left side socket output to the COF and read the pins you’ll find CKV1 up to CKV6 start by blocking all pins on the left side (from pin 1 to 16) then test, if you got a picture then you have to keep reducing the blocked pin count until you find the one causing the issue, when you find it block that pin only.

[louis313]

Hello everyone,

i have the same sony 75 inch tv with exact issue,

i have done all the test in this thread …. On Mb and t-con, and i am getting same test values as KYBOSH

and lastly tried blocking the CKV pins but still no picture,

Any other suggestions will be helpful

thanks kindly

[Diah]

Hello everyone,

i have the same sony 75 inch tv with exact issue,

i have done all the test in this thread …. On Mb and t-con, and i am getting same test values as KYBOSH

and lastly tried blocking the CKV pins but still no picture,

Any other suggestions will be helpful

thanks kindly

well i put my concern about the masking post appeared over here.. but the owner of solution take it in different way.. so i hated to complete..
at this threat we did have followed as it should signal with user didn't have high end testing equipment, so from my side i did the best to make it easy..

what we did .
1- tried display built in self-test (BIST) patterns right after abnormal input detection.. but it failed
2- we did proved the FRC circuit on MB out of business at all

what we can't testing here with home user (( V by One RX and a USI T TX interface )) to switch the Panels SPI to its high Freq such 120Hz or lower.

what i do believe there are BGA issue under the FRC Chip on MB.. but its not most.. its just calculation to read results of testing not under my hand.

[admxxx]

Hello everyone,

i have the same sony 75 inch tv with exact issue,

i have done all the test in this thread …. On Mb and t-con, and i am getting same test values as KYBOSH

and lastly tried blocking the CKV pins but still no picture,

Any other suggestions will be helpful

thanks kindly

If blocking the left side didn’t work, unblock it then block the right side and test again.
on the tcon there’s Vone test point on the left side check if the 32v voltage comes up then goes off while turning on the TV, if that’s happening it means you have short on the LCD panel.

[Diah]

the most stupid things going on web who talking on VGH VGL VCOM VEVD..etc.
T-CON VCC are 12V standard ... so where will be the T-CON PWM bring this Voltage over this supply?? its shown on yours DM as V high ... but its just Current Freq x resistances .. current Freq provided by Vido source which it come from Decoder or from FRC.

so can some one tell me from which ass come this 32V.. stop please spreading sinnlose theory of some things you never went deep to understand how it work.

[lotas]

The panel cannot be powered by 12 volts alone; it is supplied with many voltages, including VGH with oversupply + 25-32v (depending on the size of the panel) and this voltage is supplied by a DC/DC boost converter installed on the t-con.

[Diah]

The panel cannot be powered by 12 volts alone; it is supplied with many voltages, including VGH with oversupply + 25-32v (depending on the size of the panel) and this voltage is supplied by a DC/DC boost converter installed on the t-con.

wrong. ... read Timing Control boards function provided by Vestel., dont give here cut of crazy one posted over net

[lotas]

Well then, what else can we talk about if everyone is stupid and builds panel production engineers incorrectly....

Read at your leisure


https://tvrepairsolution.blogspot.co...lcd-panel.html

[Diah]

Well then, what else can we talk about if everyone is stupid and builds panel production engineers incorrectly....

its not about Design.. we are talking on method of Electronic Mathematics and component , PWM alone can do DC to Dc step down.. over the limited VCC proider it need Current Freq. this is provided via LVDS from FRC or Decoder.

[Diah]

by the way lotas i do find Vestel service manual or parts documentation are trusted source over all other brands

[Davi.p]

there is some problems i think Lotas list, 3,3v for my memory is called usually Vcc, or when Vcc are split in two there is V3D3 / Vcc33.. and V1D8/Vcc18 (for 1,8v)... AVdd is usually in the range of 15-17, from what i seen, but i mean usually.. for the rest i don't speak, it's basic lcd info..

[admxxx]

At least in my TV the dc-dc converter was on the tcon, there’s puck converters and there’s power manamgent IC (two of them one for each half of the panel that responsible for sub voltages (generated from the 12v main rail) those IC have short current detection that will cut the sub voltages in case a short detected that’s why as soon as you power up the TV the Vone spikes to 32v then cut off. I do a lot of electronics repairs but this is my first attempt on LCD panels. There’s no service manual for the tcon of the TV I have but I was able to theoretically figure it out. If you check any LVDS Pinot out you’ll notice that there’s no PWM (except for back light on smaller panels) and that’s definitely means that all sub voltages generated on the TCON from the main 12v feed via on board dc-dc converter and power management IC.

[Diah]

At least in my TV the dc-dc converter was on the tcon, there's puck converters and there's power manamgent IC (two of them one for each half of the panel that responsible for sub voltages (generated from the 12v main rail) those IC have short current detection that will cut the sub voltages in case a short detected that's why as soon as you power up the TV the Vone spikes to 32v then cut off. I do a lot of electronics repairs but this is my first attempt on LCD panels. There's no service manual for the tcon of the TV I have but I was able to theoretically figure it out. If you check any LVDS Pinot out you'll notice that there's no PWM (except for back light on smaller panels) and that's definitely means that all sub voltages generated on the TCON from the main 12v feed via on board dc-dc converter and power management IC.

any short will make spike at V then down in the protection circuit .... at other hand we do know the T-CON have PWM. but you still talking on VDC nothings about Freq or Currents. what you see on yours DM in V DC mode its not correct when the subject at T_CON.

[KYBOSH]

If blocking the left side didn’t work, unblock it then block the right side and test again.
on the tcon there’s Vone test point on the left side check if the 32v voltage comes up then goes off while turning on the TV, if that’s happening it means you have short on the LCD panel.

Thank you for coming back to explain this.
My apologies as I have been swamped as its the end of the year.

So I tried blocking off PINS 1-16 as instructed but I did not see any change on the screen.
I then tried the opposite side with the same results.
I checked the voltage of VONE but it never registered any voltage other than 0.015v.
It never jumped to 32 when I turned the TV on.

[admxxx]

Thank you for coming back to explain this.
My apologies as I have been swamped as its the end of the year.

So I tried blocking off PINS 1-16 as instructed but I did not see any change on the screen.
I then tried the opposite side with the same results.
I checked the voltage of VONE but it never registered any voltage other than 0.015v.
It never jumped to 32 when I turned the TV on.

Hi, the other side must be also from left not right. Also, the count on right side should be start from the test points (check the label on the tcon pins to understand where are the CKV and CKVB lines

[KYBOSH]

Hi, the other side must be also from left not right. Also, the count on right side should be start from the test points (check the label on the tcon pins to understand where are the CKV and CKVB lines

Than you for this.
Just to clarify:
On the LEFT side I am to block off PINS 12-26?
Those pins correspond to:
CKV1 = PIN 12
CKV2 = PIN 13
CKV3 = PIN 14
CKV4 = PIN 15
CKVB1 = PIN 16
CKVB2 = PIN 17
CKVB3 = PIN 18
CKVB4 = PIN 19
STVP = PIN 20
CKV6 = PIN 21
CKVB6 = PIN 22
CKV5 = PIN 23
CKVB5 = PIN 24


Then if that doesn't work I should block off PINS 12-26 on the RIGHT side?
There are no markings on the RIGHT side denoting which pins are CKV or CKVB.

[lotas]

No, they are in this part...

[KYBOSH]

lotas

admxxx
No joy....

Tried covering both sides and no change in the screen whatsoever.
I could hear the OCD music playing and the TV was responsive to remote.
Just no visual sign of life on the Display.