Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards. Help

[mkoser]

Hello,

First off, I am a noob to this forum. Sorry for immediately begging for help.

I am experienced with vacuum tube technology, and have restored a number of those older sets. I'm new to LED/LCD technology.

I picked up a Toshiba 55L310U Rev. A from the side of the road. I took it home and it was completely dead. Would not respond at all. Could not see any obvious physical damage to the screen or any parts. the set was completely clean (no dust or anything) and the screen bezel still had the plastic film on it. It looked basically brand new. The power cord seemed to be wrapped and secured with a cable tie. The remote and user manual was in a plastic bag taped to the back of the set.

Opened it up, and found one of the electrolytics on the power board was bulging. Replaced that and the rest as a precautionary measure with the exact same value.

The set now responded when pressing the power button by:
1) Flashing the standby light 3 times.
2) Illuminating the backlight in a sequence of "Bright" for about a second, "Medium" for a second, and then "Dim" for a second.

After that, the set sits idly, with the backlight on "dim."

There is no logo on screen, or any picture. I can't test audio, because I don't know the menu, in order to find an active input.

After about 5 minutes sitting in this state, 4 very faint grey vertical bars appear on the left side of the screen.

I can't find a schematic, so I decided to fire up the parts cannon. I ordered a supposedly working power supply board and installed it, thinking that maybe something else on that board was wonky. No change.

Frustrated (I'm sure we've all been there) and leaving for a work trip, I just fired up the cannon again and ordered a main board. It arrived and I installed it. No change. I'm at about $80 in parts.

This is where I hope someone can help me. Again, I'm a newbie and don't completely understand this technology yet. It appears that I have a Tcon board that is part of the LCD panel. Is that correct?

Any tips or tricks to determining what the issue could be? I've searched the forums and can't seem to find any info that exactly matches what I have, and what I have going on.

Thank you very much. My kids are desperately begging me to get this set up and running!

Thanks,

MK

[budm]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

We need good clear pictures of the whole backside of the TV showing all the boards so we can see what we are dealing with.

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

We need good clear pictures of the whole backside of the TV showing all the boards so we can see what we are dealing with.

Thank you for the reply. Here are some photos. Hope this will help you help me!

Thank you!

mk

[R_J]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

Check the voltage on the fuse on the integrated t-con board, It is usually +12 volts, check for voltage on both sides of the fuse

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

Check the voltage on the fuse on the integrated t-con board, It is usually +12 volts, check for voltage on both sides of the fuse

Yep. 12v on both sides...

[R_J]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

Do you have a scope? if you do, you can check the lvds cable between the main board and panel to see if there is any video signal on it.

[budm]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

https://www.badcaps.net/forum/attach...5&d=1573080764
Try disconnecting that white flat ribbon between the two tab bonding/T-con boards to see what you will get on the screeen.
You will also need to test Voltages at VGH, VGL, AVDD, ect. test points on that integrated T-CON board.

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

https://www.badcaps.net/forum/attach...5&d=1573080764
Try disconnecting that white flat ribbon between the two tab bonding/T-con boards to see what you will get on the screeen.
You will also need to test Voltages at VGH, VGL, AVDD, ect. test points on that integrated T-CON board.

Same result. Nothing. My scope is currently kaput. It's been on the bench for a year with bad caps. Need to get that done.

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

https://www.badcaps.net/forum/attach...5&d=1573080764
Try disconnecting that white flat ribbon between the two tab bonding/T-con boards to see what you will get on the screeen.
You will also need to test Voltages at VGH, VGL, AVDD, ect. test points on that integrated T-CON board.

I am also not sure where to test voltages... I don't see any voltages printed on the board...

[budm]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

You need to look for the Voltage test points on that T-CON board, your pictures are not clear enough to see them or if they provide the test points or not.

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

You need to look for the Voltage test points on that T-CON board, your pictures are not clear enough to see them or if they provide the test points or not.

Here are some more photos.

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

Here are some more photos.

Sorry. Here they are.

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

Sorry. Here they are.

Last two.

[budm]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

Example: https://www.badcaps.net/forum/attach...0&d=1573089237
You can see VDD13 test point.
More here: https://www.badcaps.net/forum/attach...5&d=1573089237
VGA, VGH, etc.
BTW, you do know how to remove/install SMD devices, correct?

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

Example: https://www.badcaps.net/forum/attach...0&d=1573089237
You can see VDD13 test point.
More here: https://www.badcaps.net/forum/attach...5&d=1573089237
VGA, VGH, etc.
BTW, you do know how to remove/install SMD devices, correct?

VDD13 1.3v
VGA -5.4v
VGH 23.9v

Do these seem correct? Again. Please excuse me noobness.

[budm]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

VDD13 1.3v
VGA -5.4v
VGH 23.9v

Do these seem correct? Again. Please excuse me noobness.

My typo for VGA, it is VGL.
The Voltages look correct, but you also need to find AVDD, it is used for running the COF.

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

My typo for VGA, it is VGL.
The Voltages look correct, but you also need to find AVDD, it is used for running the COF.

Thank you for your help so far.

I'll be looking for these tonight!

MK

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

Hey there. Sorry I just disappeared. My day job got crazy!
I’m planning to start poking around again next week.

Thank you for all the help so far!

[Unspun01]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

The faint grey vertical bars suggest bad "TCONN" (it is integrated into main board), or bad panel.

Without testing any voltages, can you place your finger on surface of each large black IC on the long narrow boards that are bonded to the panel itself (IC6, IC7, IC8, etc)? Specifically the one IC8 (with marking CSF11) that is mounted 45 degrees to the rest of the board? Can you please let us know if any of these get hot?

I had a smaller but similar panel that worked briefly upon power on for a second or two, but then that diagonally mounted IC gets extremely hot and then all kinds of visual problems.

On my TV, either that IC is the issue, or one of the small irreplaceable ICs on the TAB bond ribbon cables to the panel is bad. It is possible to replace IC8, but the tab bond IC on the ribbon cable is not replaceable.

This could be a bad panel.

[mkoser]

Re: Toshiba 55L310U Rev. A No picture Good Backlight Replaced Main and Power boards.

The faint grey vertical bars suggest bad "TCONN" (it is integrated into main board), or bad panel.

Without testing any voltages, can you place your finger on surface of each large black IC on the long narrow boards that are bonded to the panel itself (IC6, IC7, IC8, etc)? Specifically the one IC8 (with marking CSF11) that is mounted 45 degrees to the rest of the board? Can you please let us know if any of these get hot?

I had a smaller but similar panel that worked briefly upon power on for a second or two, but then that diagonally mounted IC gets extremely hot and then all kinds of visual problems.

On my TV, either that IC is the issue, or one of the small irreplaceable ICs on the TAB bond ribbon cables to the panel is bad. It is possible to replace IC8, but the tab bond IC on the ribbon cable is not replaceable.

This could be a bad panel.

Hi there. Thanks for the tips. I let the set run about 20 minutes and then did the finger test and IR thermometer test on those IC's. Nothing remarkable.

Haven't had a chance to keep metering voltages.

Thanks for the help so far!