Sony XBR-65850F No Picture (Backlights/Audio Okay)

[philtvman]

This is a similar case to this thread

Picked up this unit from a guy who said he took it to a repair shop and they weren't able to fix it. The TV turns on, backlights and sound both work, but there is no picture. The thread linked above had an issue with a shorted MLCC on one of the panel driver boards. I went through them all, and I couldn't find anything shorted (unless I was measuring them wrong).

All voltages going from the PSU to the TCON/Main look nominal. TCON is getting the 12V and it's passing through the fuse just fine.

One thing I noticed is that it looks like there may be a diode that is missing on the far left (looking at it from the back) driver board...D104. There is a matching spot on the right side (D204) that has the part still in place. I have no idea if it is the exact same part, but I would tend to believe it probably is. It has 6514P 1829 marked on it. Unfortunately, I am having zero luck finding this part online anywhere.

Anybody have any advice?

[budwich]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

goes look like someone "modified" the board with a soldering iron ... :-)

Try disconnecting the tcon to panel cable going to that side with the missing component and see if that changes what happen on the screen.... which is?

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

goes look like someone "modified" the board with a soldering iron ... :-)

Try disconnecting the tcon to panel cable going to that side with the missing component and see if that changes what happen on the screen.... which is?

Disconnecting that side still has no picture unfortunately. The disconnected side is black obviously, but still no picture on the other side.

[budwich]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

"normally", if one disconnects the tcon to panel cable, the result is a white screen (although some sets display black).

although you say the voltages from the PSU to the main / tcon look "nominal" can you list the labels / pins and then post those measurements for each... do this for the set in standby / power plugged in and then again with power ON / set running so the forum can see what you are saying in "more words"... :-)

further, there are a number of voltages labeled on the tcon (left side of your posted picture). Then again you should carefully measure and post with the label... these may indicate what area is missing / not right to get a display.

Lastly, also post a picture showing the whole back with connected cards so the forum can see how things are connected.

on the post that you referenced, post 99 appears to point to the area for the resolution. Based on that, you should be looking at either a short OR open.

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

"normally", if one disconnects the tcon to panel cable, the result is a white screen (although some sets display black).

although you say the voltages from the PSU to the main / tcon look "nominal" can you list the labels / pins and then post those measurements for each... do this for the set in standby / power plugged in and then again with power ON / set running so the forum can see what you are saying in "more words"... :-)

further, there are a number of voltages labeled on the tcon (left side of your posted picture). Then again you should carefully measure and post with the label... these may indicate what area is missing / not right to get a display.

Lastly, also post a picture showing the whole back with connected cards so the forum can see how things are connected.

on the post that you referenced, post 99 appears to point to the area for the resolution. Based on that, you should be looking at either a short OR open.

I have attached a picture of the back and of the voltages. What is the best way to check the MLCC capacitors for a short or open? I went through them all with my multimeter in continuity mode. Would the apparent missing diode not be a cause for the TCON not processing correctly?

[budwich]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

good work. Those values look OK. As mentioned there are voltages on the tcon that maybe of value... as read in the referenced link, feakaftr8 checked those also.

Certainly a missing component is an issue... assuming you know that the component is indeed missing. Manufacturers don't always populate every labeled device / component. Hopefully, perhaps someone will have info on that diode.

From the posted picture of the back, another test is to keep all the cables connected but disconnect the "U" ribbon that runs between the bottom edge boards. Do this one at a time and see if that changes anything.

Also, it appears, like the linked reference, that there is some IC differences between the right and left "half" of the panel on those edge boards.

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

good work. Those values look OK. As mentioned there are voltages on the tcon that maybe of value... as read in the referenced link, feakaftr8 checked those also.

Certainly a missing component is an issue... assuming you know that the component is indeed missing. Manufacturers don't always populate every labeled device / component. Hopefully, perhaps someone will have info on that diode.

From the posted picture of the back, another test is to keep all the cables connected but disconnect the "U" ribbon that runs between the bottom edge boards. Do this one at a time and see if that changes anything.

Also, it appears, like the linked reference, that there is some IC differences between the right and left "half" of the panel on those edge boards.

Sorry to be ignorant, but how do I go about testing the voltages on the TCON board. I did notice that freakaftr8 was able to measure the voltages going from the TCON to the panel, but I'm not sure how to do that.

[budwich]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

there are labels and circuit board "points" where those "label voltages" can be found.

somewhat related to this. You indicate a difference between right and left bottom edge boards in terms of a missing component. You can check the voltage (to ground) on the contacts and compare them from each side. Might indicate something.

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

there are labels and circuit board "points" where those "label voltages" can be found.

somewhat related to this. You indicate a difference between right and left bottom edge boards in terms of a missing component. You can check the voltage (to ground) on the contacts and compare them from each side. Might indicate something.

Sorry, I feel blind. Where are the labels?

[budwich]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

As I indicated on the left side of the tcon... things with "Vxxxxx" are of interest.... eg. vcom1, vcom2, etc...

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

As I indicated on the left side of the tcon... things with "Vxxxxx" are of interest.... eg. vcom1, vcom2, etc...

Attached is a closer up picture of the VCOM, VST, VGH lines, where exactly are the test points for them? I thought it would have exposed test pads.

There is also some variation between what happens when the driver boards are unplugged, I've tried all different variations. Regardless of what I do though, there is never a partial image. Attached is the result of unplugging the driver boards.

Thank you for your help, I really appreciate it.

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

What is the best method for testing MLCCs? Since this is a common failure point for this symptom.

[budm]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

What is the best method for testing MLCCs? Since this is a common failure point for this symptom.

Use Ohm meter to look for MLCC that show low resistance (<100 Ohms) readings in both directions.

[budwich]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

Attached is a closer up picture of the VCOM, VST, VGH lines, where exactly are the test points for them? I thought it would have exposed test pads.

There is also some variation between what happens when the driver boards are unplugged, I've tried all different variations. Regardless of what I do though, there is never a partial image. Attached is the result of unplugging the driver boards.

Thank you for your help, I really appreciate it.

I see that your "observations" might have been a bit different than earlier. :-)

It would appear that potentially there is an issue associated with the tcon 1 / 2 side of the panel.... maybe as it is black rather than white.... the disconnect test is a "gross test" so it is relatively open to interpretation.... but maybe helps with further focus. As I suggested earlier, there are "U" type ribbons interconnecting the bottom edge boards. Leave all the tcon cables attached and do a "disconnect test" with those "U" cables and see if anything changes.... look closely and report the outcome on the display result.

[chrismurphy]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

Main board problem ,common on this set

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

I see that your "observations" might have been a bit different than earlier. :-)

It would appear that potentially there is an issue associated with the tcon 1 / 2 side of the panel.... maybe as it is black rather than white.... the disconnect test is a "gross test" so it is relatively open to interpretation.... but maybe helps with further focus. As I suggested earlier, there are "U" type ribbons interconnecting the bottom edge boards. Leave all the tcon cables attached and do a "disconnect test" with those "U" cables and see if anything changes.... look closely and report the outcome on the display result.

Correct, I had only disconnected the 'missing component' side at first. The picture I attached showed what resulted from the unplugging of the 'U' cables (all variations). I've attached another result with a diagram. Per the linked article though, it seemed that if there was a short or open somewhere on the driver board that the TCON in these sets won't power on completely.

I went through all the MLCC with an ohmmeter. The smaller ones all tested either 2-4k Ohm and the larger ones were all OL.

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

Main board problem ,common on this set

How can I be sure of this?

[budwich]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

Correct, I had only disconnected the 'missing component' side at first. The picture I attached showed what resulted from the unplugging of the 'U' cables (all variations). I've attached another result with a diagram. Per the linked article though, it seemed that if there was a short or open somewhere on the driver board that the TCON in these sets won't power on completely.

I went through all the MLCC with an ohmmeter. The smaller ones all tested either 2-4k Ohm and the larger ones were all OL.

ok ... sorry I misread previous post with numbers... I thought they referred to the tcon cabling and not the "u" cables. hmmm... interesting about the results. As mentioned, was expecting some form of white.... but again, perhaps I misunderstand what the chart is saying. Can you post a picture of the screen for the ones that show white?.... I think I understand what you are indicating but just want to make sure. Further, what is the difference between black, grey and white?

In terms of labeling, there may not be "shiny test points" but the labels are aligned with where tracks / component circuit tabs are most likely to be associated with the label. You can "guess" a bit and use your meter (on continuity and board unplugged) to follow paths to confirm.

[jostewcrew]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

How can I be sure of this?

according to the service manual, its a tcon or panel issue.

[philtvman]

Re: Sony XBR-65850F No Picture (Backlights/Audio Okay)

there are labels and circuit board "points" where those "label voltages" can be found.

somewhat related to this. You indicate a difference between right and left bottom edge boards in terms of a missing component. You can check the voltage (to ground) on the contacts and compare them from each side. Might indicate something.

Was finally able to grab the TCON voltages, see attached.