Samsung UN55FH6030F - Confirming dead panel?

[itachi]

Backlight works on this TV but no video or OSD showing. I started poking around the TCON board and found one of the large ASICs was cold to the touch so I started checking voltages. Found a regulator getting 0.75V in and nothing out, and eventually traced the voltage rail back to one of the two ribbon cables going to the LCD panel.

Unplugging this cable brings the picture back to the other half of the panel, so am I correct in thinking the panel is toast? The ribbon cables go to those small PCBs that run along the width of the panel and have some surface mount components on them. Is there a possibility there could be a fault with this and not the panel?

[budm]

Re: Samsung UN55FH6030F - Confirming dead panel?

Start checking the DC resistance of the caps on that tab bonding board for low resistance reading, hopefully it will just shorted cap not shorted COF.

[itachi]

Re: Samsung UN55FH6030F - Confirming dead panel?

Thanks for the reply. I measured the caps to where I found the lowest resistance and removed several to be sure but no luck. The lowest resistance reading is directly under one of those chip on flex connectors so I assume its something in there.

[nomoresonys]

Re: Samsung UN55FH6030F - Confirming dead panel?

Usually if the cof has a problem it will look different than the others or be hotter etc.

[itachi]

Re: Samsung UN55FH6030F - Confirming dead panel?

That makes sense. Also unplugging that half of the panel makes it go from all black to all white. I went back and checked all the caps from one end to the other and recorded their values but once again it all pointed to the same three. CA44 (4.28 ohms), CA48 (10.36) and CH42 (11.68).

Removing them did not change the measured values and to be sure I just went and pulled the rest of them from this area. There are two more "groups" of capacitors and resistors off screen to the left, mostly identical in layout to the area shown but the resistance values read higher and higher as you measure in that direction.

[budwich]

Re: Samsung UN55FH6030F - Confirming dead panel?

Ah... but the "white" versus "black" result is somewhat important. Do you get the same result with either "side" of the tcon to panel cables disconnected? Normally, the side that is disconnected should show white.... while the other side should show some form of picture assuming you have something input or something to cause video on the screen.

If there is nothing on connected side, this usually points to no signal getting into that side of the panel. Usually this is somewhere back at the tcon or further back. You need to look closer at the tcon and measure various "labelled points" that have some form of "Vxx" type labeling to see what you find.

Further, from your just posted picture, you can see some labeling associated with the edge board. Carefully measure those points.

[itachi]

Re: Samsung UN55FH6030F - Confirming dead panel?

Ah... but the "white" versus "black" result is somewhat important. Do you get the same result with either "side" of the tcon to panel cables disconnected? Normally, the side that is disconnected should show white.... while the other side should show some form of picture assuming you have something input or something to cause video on the screen.

If there is nothing on connected side, this usually points to no signal getting into that side of the panel. Usually this is somewhere back at the tcon or further back. You need to look closer at the tcon and measure various "labelled points" that have some form of "Vxx" type labeling to see what you find.

Further, from your just posted picture, you can see some labeling associated with the edge board. Carefully measure those points.

Unplugging the left side only results in the left side going white and the right side working. Unplugging the right side only results in everything going black. The left seems to pull all the rails down to unusable levels. 3.3V goes to 0.75V, 1.8 and 17.5 go closer to 0V.

It makes sense that would happen with the low impedances I'm reading on the left edge PCB, but as I mentioned removing the suspect caps resulted in no change. There are more caps on the board, but resistance measurements indicate they're far away from where the "short" is.

[budwich]

Re: Samsung UN55FH6030F - Confirming dead panel?

:-( thanks for the added / restated observations. It would appear there is little hope...maybe.

can you provide a picture of the whole bottom edge board(s) so one can see how they are connected / interconnected. Note that there perhaps is hope because of the way that there is potentially a way to further isolate the bad section maybe using the tape cutoff method... but again slim based on what you have indicated so far. Further can you provide a screen shot of the display that shows the half white and working side.

[budwich]

Re: Samsung UN55FH6030F - Confirming dead panel?

That makes sense. Also unplugging that half of the panel makes it go from all black to all white. I went back and checked all the caps from one end to the other and recorded their values but once again it all pointed to the same three. CA44 (4.28 ohms), CA48 (10.36) and CH42 (11.68).

Removing them did not change the measured values and to be sure I just went and pulled the rest of them from this area. There are two more "groups" of capacitors and resistors off screen to the left, mostly identical in layout to the area shown but the resistance values read higher and higher as you measure in that direction.

one more question, what and or why is there what appears to be some form of staining / contamination on or near the ribbon going to the panel just above where you have removed some of the caps (ca47)? what does the rest of the edge board area look like?