Samsung UE55H7080 black screen (sound is working)

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

How can you conclude that now? Shouldn't a panel failure be better visible on the screen?

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

You need to disconnect the ribbon cables with the flip lock one at a time to see if half of the panel is working. This thread may apply https://www.badcaps.net/forum/showthread.php?t=50646

Like explained above, I did this (at least for the tcon board). Nothing changes when I disconnect one of the bottom two ribbon cables. When I disconnect either the top ribbon cable or the other cable with 6 connections, the backlight turns on.

I've spotted a 3rd LED (LED2) on the tcon board which stays off all the time. Don't know if this helps.

[neilc6]

Re: Samsung UE55H7080 black screen (sound is working)

You need to disconnect the two ribbon cables going from the tcon to the panel one at a time. NOT the two connectors you highlighted in red in post #18 you described as top connectors. If one side is working, then there is a panel fault on one side.

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

You need to disconnect the two ribbon cables going from the tcon to the panel one at a time. NOT the two connectors you highlighted in red in post #18 you described as top connectors. If one side is working, then there is a panel fault on one side.

Man, I wrote the following:

"When I disconnect one of the top cables (see red areas in attachment) of the tcon board, the backlight turns on as I switch on the TV. The backlight also turns on if both cables are disconnected. By disconnecting the bottom cables, nothing (obvious) changes." in Post #18. There I only referred to the attachment when I was talking about the two cables on the TOP. I've also disconnected the two ribbon cables at the bottom and like explained twice now, everything stays dark when I disconnect the either of the two BOTTOM ribbon cables (I marked them for you now too in the attachment in this post).

[neilc6]

Re: Samsung UE55H7080 black screen (sound is working)

Jeesh, where did you indicate that you disconnected the ribbon cables one at a time as suggested. Disconnecting the connectors on the opposite side indicates you are not doing the correct test. The first half of this thread is trying to determine if your backlights come on or not.

Nothing changes when I disconnect one of the bottom two ribbon cables.

Assumes you only checked one side.

By disconnecting the bottom cables, nothing (obvious) changes.

Assumes you disconnected both at the same time.

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

Jeesh, where did you indicate that you disconnected the ribbon cables one at a time as suggested. Disconnecting the connectors on the opposite side indicates you are not doing the correct test. The first half of this thread is trying to determine if your backlights come on or not.


Assumes you only checked one side.


Assumes you disconnected both at the same time.

I see what you mean. After the post from budwich #17 I anyway tried disconnecting also the bottom connectors to the panel (which I also tried to tell in my post). Sorry for the confusion.

I disconnected always one at a time from the bottom two connectors and neither with the right cable connected, nor with the left one connected I can see something on the screen. It stays black.

[budwich]

Re: Samsung UE55H7080 black screen (sound is working)

OK... now that "we" are talking the same thing in terms of tests, it would appear that there is an issue at the tcon to panel area... maybe. As "normally"... but maybe not for samsung / model, but when a panel is powered correctly and one of the tcon to panel cables is disconnected, the disconnected side shows white. Having said that, some sets like sony, if the panel connection is not there, then the system detects this and shut down. What happens to the sound when you do this test (tcon to panel disconnect)?

Further, your "other test" (removing the main to tcon cable) causes the backlights to turn on.... again a different observation than what started this thread and title.... so did you then redo your measurements at the power board to see what is different?

Please remember that the forum can only help you if you provide clear and concise answer as the forum can't see your set or your testing.

[nomoresonys]

Re: Samsung UE55H7080 black screen (sound is working)

Maybe check those little capacitors on tcon for shorts, diode mode one probe on each side, if you find one shorted, could indicate a problem on driver board between tcon and panel.

[budm]

Re: Samsung UE55H7080 black screen (sound is working)

OK, let me get this straight:
If you have both of the ribbon cables between the LCD panel and the T-CON board disconnected, and the cable between T-CON and the main board is still in place then the backlighs will be on when turning the TV ON, correct?
If that is the case the put the ribbon cables back in place and then check the resistance between GND test points VGH, VGL, VCOM, VCC, VDD,... to see what you get and report the readings.

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

OK... now that "we" are talking the same thing in terms of tests, it would appear that there is an issue at the tcon to panel area... maybe. As "normally"... but maybe not for samsung / model, but when a panel is powered correctly and one of the tcon to panel cables is disconnected, the disconnected side shows white. Having said that, some sets like sony, if the panel connection is not there, then the system detects this and shut down. What happens to the sound when you do this test (tcon to panel disconnect)?

Further, your "other test" (removing the main to tcon cable) causes the backlights to turn on.... again a different observation than what started this thread and title.... so did you then redo your measurements at the power board to see what is different?

Please remember that the forum can only help you if you provide clear and concise answer as the forum can't see your set or your testing.

I'm sorry if it was unclear but that the backlight is working at all came up during the tests recommended here. I didn't know that when I was starting the thread.

I repeated the experiments and made a table of the results (see attachments). I always disconnected one cable at a time, so 3 were plugged, 1 was unplugged for this tests.

Maybe check those little capacitors on tcon for shorts, diode mode one probe on each side, if you find one shorted, could indicate a problem on driver board between tcon and panel.

In a particular area of the tcon board? There are a lot of capacitors on there.

OK, let me get this straight:
If you have both of the ribbon cables between the LCD panel and the T-CON board disconnected, and the cable between T-CON and the main board is still in place then the backlighs will be on when turning the TV ON, correct?
If that is the case the put the ribbon cables back in place and then check the resistance between GND test points VGH, VGL, VCOM, VCC, VDD,... to see what you get and report the readings.

When disconnecting both ribbon cables which go to the panel (marked with Ex3 and Ex4 in this attachment) and keep the cables marked with Ex1 and Ex2 plugged, the screen stays black, hence the backlight stays off.
Where can I find VGH, VGL, ...? I can't find these writings on the tcon board.

[budm]

Re: Samsung UE55H7080 black screen (sound is working)

I do not understand you chart in the Backlights row.
You show ON (EX1), ON (EX2), OFF (EX3), OFF (EX4)
You have 4 connectors so what combination of the four connectors have to be to get the backlight on?

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

The sound and backlight rows belong to the experiments in the same column respectively. As I noted, for these tests I always disconnected one cable at a time. Hence, I got the backlight on steadily by either removing cable Ex1 or Ex2.

In a later text, I've also tried to disconnect two cables at a time, namely:
Ex1 and Ex2 unplugged; Ex3 and Ex4 plugged: Backlight goes on steadily, sound working
Ex1 and Ex2 plugged; Ex3 and Ex4 unplugged: Backlight stays off, sound working

[budwich]

Re: Samsung UE55H7080 black screen (sound is working)

I'm sorry if it was unclear but that the backlight is working at all came up during the tests recommended here. I didn't know that when I was starting the thread.

I repeated the experiments and made a table of the results (see attachments). I always disconnected one cable at a time, so 3 were plugged, 1 was unplugged for this tests.



In a particular area of the tcon board? There are a lot of capacitors on there.



When disconnecting both ribbon cables which go to the panel (marked with Ex3 and Ex4 in this attachment) and keep the cables marked with Ex1 and Ex2 plugged, the screen stays black, hence the backlight stays off.
Where can I find VGH, VGL, ...? I can't find these writings on the tcon board.

that helps a bit. Again, you are doing more than was requested but not reporting enough.... in this case, you make no mention of what happens to the sound in the cases that you have now put forth.

Further, your "4 cases" show differences for when the back light is supposed lit (you didn't actually state this... but the guess is the first two instances) versus when they are not lit... pdim differences.

It would appear from this that the problem is at the tcon / panel since when you disconnect incoming "controls / powerings" to the tcon, the backlighting comes on but disconnecting some form of tcon to panel results in "nothing".

Look at the tcon for various voltage test points and do some measurements / label list... this will likely move you closer.

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

that helps a bit. Again, you are doing more than was requested but not reporting enough.... in this case, you make no mention of what happens to the sound in the cases that you have now put forth.

Yes, I'm doing more test than stated because I thought it could be helpful (and if not, at least it shouldn't be a harm).

I brought the new cases up because of this request:

I do not understand you chart in the Backlights row.
You show ON (EX1), ON (EX2), OFF (EX3), OFF (EX4)
You have 4 connectors so what combination of the four connectors have to be to get the backlight on?

And sound is working for all test cases I've tried yet.

Further, your "4 cases" show differences for when the back light is supposed lit (you didn't actually state this... but the guess is the first two instances) versus when they are not lit... pdim differences.

Yes, which I already tried to note twice. And I've tried to state it more clear in the table attached above. And yes, the behavior of the backlight correlates with the P_DIM voltages. If they are 0V it is turned off, if they are around 3.5V it is lit. The voltage levels were only measured on the power supply board till now.

It would appear from this that the problem is at the tcon / panel since when you disconnect incoming "controls / powerings" to the tcon, the backlighting comes on but disconnecting some form of tcon to panel results in "nothing".

Look at the tcon for various voltage test points and do some measurements / label list... this will likely move you closer.

Exactly these are my observations till now. Like explained in my last post, I've already tried to find some pins / label lists on the tcon board but I found nothing which is really meaningful in my opinion. I hope it's somehow readable in the attachments but voltage levels at e.g. C215 won't mean much to you.

[budwich]

Re: Samsung UE55H7080 black screen (sound is working)

hopefully you are not looking for VXXX where XXX is 12.0, 20.0, etc.... you are looking for things that start with "V" (of course, not VGAxx... which a video signal).
Further, you have looked under the plate / heat sink area?

IF in doubt, do some tracing of any voltages coming on cables directly from the power suppy or main board that you already know about... follow these towards the outputs to cable areas to the panel. There are panel drive voltages there as BUDM suggested... they may not be EXACTLY labelled the same but close.

In addition, the tcon to panel cables terminate on bottom edge boards which also may have some labelling that may help.

Lastly, because you have sound for all your "test scenarios", indicates that the main board is NOT shutting down the system because of a "detectable fatal error" (eg. panel disconnected)... so to me, this points to a problem at the tcon and beyond... hence that should be your focus.

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

hopefully you are not looking for VXXX where XXX is 12.0, 20.0, etc.... you are looking for things that start with "V" (of course, not VGAxx... which a video signal).

Of course not, would be nice though if they'd tell you "hey, this voltage needs to be xxx"

Further, you have looked under the plate / heat sink area?

Also a no here, I am afraid that this is mounted on an IC with a heat-conductive paste and I don't have one at home at the moment.

IF in doubt, do some tracing of any voltages coming on cables directly from the power suppy or main board that you already know about... follow these towards the outputs to cable areas to the panel. There are panel drive voltages there as BUDM suggested... they may not be EXACTLY labelled the same but close.

In addition, the tcon to panel cables terminate on bottom edge boards which also may have some labelling that may help.

Lastly, because you have sound for all your "test scenarios", indicates that the main board is NOT shutting down the system because of a "detectable fatal error" (eg. panel disconnected)... so to me, this points to a problem at the tcon and beyond... hence that should be your focus.

Here pops again the question up how I can follow them. Without a circuit plan this is nearly impossible without removing the tcon board from the tv.

For the labeling of the connections from the tcon to the panel I'd have to remove the lower cover to get to the other side of the cable. Probably there are some pin namings?

I found the pin names of some of the pins of the ribbon cable from the main board to the tcon (see attachment). Would they help? They are called something like EVEN_TX, ODD_TX (probably some serial connection?). I found Panel_VCC which is always about 13V on the mainboard.

I can nicely measure them on the mainboard but on the tcon board it's hard to reach a proper point because measuring at the plug (terminal where the cable is plugged onto the board) is nearly impossible because the connections are so small.

Still my biggest problem is to find proper pin namings on the tcon board to deliver suitable information.

[budm]

Re: Samsung UE55H7080 black screen (sound is working)

I see test points on T-CON, I.E. 1.1V, 1.2V, 2.5V, 3.3V, HAVDD, HVIN,... and probably more under the heatsink.
Samsung BN95-01315A T-Con Board
https://www.shopjimmy.com/samsung-bn...con-board.htm#

[budwich]

Re: Samsung UE55H7080 black screen (sound is working)

Of course not, would be nice though if they'd tell you "hey, this voltage needs to be xxx"



Also a no here, I am afraid that this is mounted on an IC with a heat-conductive paste and I don't have one at home at the moment.



Here pops again the question up how I can follow them. Without a circuit plan this is nearly impossible without removing the tcon board from the tv.

For the labeling of the connections from the tcon to the panel I'd have to remove the lower cover to get to the other side of the cable. Probably there are some pin namings?

I found the pin names of some of the pins of the ribbon cable from the main board to the tcon (see attachment). Would they help? They are called something like EVEN_TX, ODD_TX (probably some serial connection?). I found Panel_VCC which is always about 13V on the mainboard.

I can nicely measure them on the mainboard but on the tcon board it's hard to reach a proper point because measuring at the plug (terminal where the cable is plugged onto the board) is nearly impossible because the connections are so small.

Still my biggest problem is to find proper pin namings on the tcon board to deliver suitable information.

well you are either thinking too much or not enough. :-)

First when asked to "trace a circuit"... you don't need to have power to it.... in fact it is better not to have any. You use a "resistance based trace"... that is you put your probe at one point which can see or identify readily easily and then take the other probe and see "logically" which the circuit / cable run... etc might run.... hopefully your meter has a "tone feature" which gives you a beep when it detects a "short" which would means that the two points are electrically on the same "copper". From this, you can readily move around any board to find points which are connected and more readily accessable for probing if you need to do a future voltage measurement. Hopefully, this understandable.

Further, the picture that you provide DOES NOT show the edge boards that are along the bottom of the set that the tcon cables are connected to. Those edge boards also have labels and are highly likely to have potentially faulty components that cause voltage issues between the tcon and the panel. Hence the "hints" of where to look. Do some reading / searching on edge boards to see what you are looking for.

[Steradiant]

Re: Samsung UE55H7080 black screen (sound is working)

well you are either thinking too much or not enough. :-)

First when asked to "trace a circuit"... you don't need to have power to it.... in fact it is better not to have any. You use a "resistance based trace"... that is you put your probe at one point which can see or identify readily easily and then take the other probe and see "logically" which the circuit / cable run... etc might run.... hopefully your meter has a "tone feature" which gives you a beep when it detects a "short" which would means that the two points are electrically on the same "copper". From this, you can readily move around any board to find points which are connected and more readily accessable for probing if you need to do a future voltage measurement. Hopefully, this understandable.

Further, the picture that you provide DOES NOT show the edge boards that are along the bottom of the set that the tcon cables are connected to. Those edge boards also have labels and are highly likely to have potentially faulty components that cause voltage issues between the tcon and the panel. Hence the "hints" of where to look. Do some reading / searching on edge boards to see what you are looking for.

Thanks, it was absolutely understandable and I thought of this but honestly, I don't see where this should get me. I can follow a trace but don't know what the trace is all about or what voltage I should have there. For me only measurement points are meaningful, where I have at least a hint if they should be 0 or not.

I also opened the bottom now (pic attached) but again no meaningful labels for me. On the other hand, like already stated above, we think it shouldn't be a problem of the panel or the connection from the tcon to the panel because disconnecting the two cables to the panel didn't change a thing.

[budwich]

Re: Samsung UE55H7080 black screen (sound is working)

but honestly... I don't understand you. If you know where the voltage is at say board A / connect x, pin y. Put you one probe there, ensure there is NO power applied to the system else this could destroy your meter. Put your meter on resistance / short beep test mode. Take your other probe and go to board b (assuming it is connected in some form to A, you don't even have to know where or how it is connected). Use probe to see where the meter register a short / 0 resistance anywhere on board B... ALL those areas will be connected to the "reference point" of the other probe. IF you are "wise", you will find points that are readily accessible and safe to probe WHEN you do your next test for voltage. Thus you have now found a "safe" place to place your probe to check for voltage at points on the board... which you "complained" about that weren't easy to access.... that's because you are trying to access the point at / or near the connectors which the lines are very close.... be smarter and find points further away / near "touchable" components.

Once you do this you will be readily able to follow voltages thru the circuit without knowing EVERYTHING about the circuit out side of say, this a resistor, this is capacitor... etc. IF the voltage is on one side of component, and not on the other, then you have likely found the potential problem.... you can go from there.

Again hope you understand this. Further, once you follow voltages thru the board, you will likely come across other components that you can find spec sheets on or people on the forum know what happens if a voltage comes in but not out (depending on conditions). You will get there. Yes, a schematic is nice but it isn't totally necessary and lots here, "walk" thru circuits with little more than a meter and some eyes.

As for the new picture, it shows LOTS of voltage points.... and some which I do believe match those on the tcon... so a voltage at edge board needs to match one on the tcon.

Still further, most voltage points are not going to read 0 and be labelled... IF they do, that is a good place to start digging deeper. Further, IF a voltage point does read 0, then it is likely being grounded or the driving component is dead. Thus another test would be a resistance test (with power OFF) to see if those voltage labelled points are grounded / 0 resistance.

LASTLY... did you read what budm posted????

Really, who cares if YOU don't know what the voltages are supposed to be... that is why you are posting in the forum with a list showing the label and voltage reading.... the forum will then help you understand whether the voltage is good, bad or otherwise.