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Old 04-25-2011, 12:59 PM   #1
rhino18e
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Default Sanyo DP46848 screen half dark

I have this TV that when I turn it on the left side of the screen is dark, then after about 10 to 20 minutes the left side (which I think are the backlights) will start to flicker and then will come on and stay on until I turn off the TV. Then if I turn it back on it does the same thing.
Any help would be appreciated

Thanks in advanced
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Old 04-25-2011, 01:02 PM   #2
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Default Re: Sanyo DP46848 screen half dark

Forgot to attach pics

middle pic is after 20 mins or so
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Old 04-25-2011, 01:07 PM   #3
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Default Re: Sanyo DP46848 screen half dark

I don't have a definitive answer and have way less experience on the TVs versus the computer LCDs, but you probably will have to take the TV apart and post pictures of the internal boards. Look for bad capacitors, poor solder joints, etc.
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Last edited by retiredcaps; 04-25-2011 at 01:16 PM..
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Old 04-25-2011, 01:12 PM   #4
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Default Re: Sanyo DP46848 screen half dark

Quote:
Originally Posted by rhino18e View Post
I have this TV that when I turn it on the left side of the screen is dark, then after about 10 to 20 minutes the left side (which I think are the backlights) will start to flicker and then will come on and stay on until I turn off the TV. Then if I turn it back on it does the same thing.
Any help would be appreciated

Thanks in advanced
In every case problems such as this are due to malfunctions of the panel in some way. Power supply problems seem remote to this effect.

T-Con is unlikely. Connections from the T-con to the panel are a possibility.
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Old 04-25-2011, 01:44 PM   #5
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Default Re: Sanyo DP46848 screen half dark

Definitely looks like backlights to me. Unusual that it wouldn't trigger an inverter shutdown. A picture of the back of the TV (with the cover off) would be a big help.

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Old 04-25-2011, 01:49 PM   #6
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Default Re: Sanyo DP46848 screen half dark

Pics of the power supply and video card

solder joints look good on the power supply
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Old 04-25-2011, 02:11 PM   #7
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Default Re: Sanyo DP46848 screen half dark

The pins on the two inverter transformers (1st photo upper left) look a little discolored (2nd photo). Suggest you try resoldering all the inverter transformer pins with fresh solder. Also, resolder the leads of the two heat-sinked mosfets to the right of the inverter transformers.
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Old 04-25-2011, 02:11 PM   #8
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Default Re: Sanyo DP46848 screen half dark

The power and signal cards are in a depression of the back cover, I took them out and hooked them up like the back cover isn't there
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Old 04-25-2011, 02:33 PM   #9
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Default Re: Sanyo DP46848 screen half dark

Quote:
Originally Posted by jetadm123 View Post
The pins on the two inverter transformers (1st photo upper left) look a little discolored (2nd photo). Suggest you try resoldering all the inverter transformer pins with fresh solder. Also, resolder the leads of the two heat-sinked mosfets to the right of the inverter transformers.
That area is a little darker. I will resolder all points you made, I noticed there is a solder bridge near the one mosfet and a diode should I fix this too?
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Old 04-25-2011, 04:45 PM   #10
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Default Re: Sanyo DP46848 screen half dark

I circled a couple of what looks like solder ring cracks to me (or is it the lighting)? You have the best view and if you use a 10x magnifier you might see more?
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Old 04-25-2011, 05:38 PM   #11
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Default Re: Sanyo DP46848 screen half dark

This tv has master and slave inverters. I have seen these shut down when ccfls get to a certain point of failure and it only takes a couple. The pattern looks odd though and not sure of the bulb layout on this panel.
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Old 04-25-2011, 06:30 PM   #12
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Default Re: Sanyo DP46848 screen half dark

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This tv has master and slave inverters. I have seen these shut down when ccfls get to a certain point of failure and it only takes a couple. The pattern looks odd though and not sure of the bulb layout on this panel.
By the pictures in post #8 the inverters are on either side of the panel. That suggests the CCFLs run horizontally, which makes it likely that this is NOT a CCFL problem and Village Electronics is right.

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Old 04-25-2011, 07:44 PM   #13
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Default Re: Sanyo DP46848 screen half dark

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By the pictures in post #8 the inverters are on either side of the panel. That suggests the CCFLs run horizontally, which makes it likely that this is NOT a CCFL problem and Village Electronics is right.

PlainBill
I took the black plastic off the sides and there are master and slave inverters. I resoldered the power supply transformers and the mosfets and have yet put it back together to see if anything changed. I found the specs for the panel if that helps. Will post results when reassembled.
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Old 04-25-2011, 08:13 PM   #14
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Default Re: Sanyo DP46848 screen half dark

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Originally Posted by retiredcaps View Post
I circled a couple of what looks like solder ring cracks to me (or is it the lighting)? You have the best view and if you use a 10x magnifier you might see more?
That's refection, I took the picture outside in the shade. I looked at it with a 4x magnifier and it looks good.
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Old 04-26-2011, 09:59 AM   #15
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Default Re: Sanyo DP46848 screen half dark

After resoldering the transformers and mosfets there is no change. Could it be the master or slave boards?
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Old 08-31-2011, 01:55 AM   #16
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Default Re: Sanyo DP46848 screen half dark

I apologize in advance for bringing up an old thread, but I'm having the exact same issue. I've done a bit of troubleshooting on my own. I removed the main board (video card, signal card, whatever you call it) and looked around for dark spots which I didnt find any. The problem goes away when you tap on the upper left corner of the housing around the display which makes me think its some sort of connection problem. I hooked the signal board back up but I didnt screw it in all the way. I wanted for the problem to occur and then wiggled the signal board to see if the problem went away, and it did not. So that almost verifys for me that it is not a problem with the signal board. Is it worth it to remove then entire back panel and check for loose connections or anything else? What else should I look for? Is there a part that I can replace myself fairly easily? Let me know if there is anything else you would like me to try, if you need pictures of anything.

Thanks
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Old 08-31-2011, 01:59 AM   #17
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Default Re: Sanyo DP46848 screen half dark

Also, I know it is not a backlight issue as the top part of the screen goes a little glitchy. Its hard to explain, so here is a video I took of the problem a while back. http://www.youtube.com/watch?v=9Mi-q8kMAwc
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Old 08-31-2011, 06:06 AM   #18
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Default Re: Sanyo DP46848 screen half dark

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I apologize in advance for bringing up an old thread, but I'm having the exact same issue. I've done a bit of troubleshooting on my own. I removed the main board (video card, signal card, whatever you call it) and looked around for dark spots which I didnt find any. The problem goes away when you tap on the upper left corner of the housing around the display which makes me think its some sort of connection problem. I hooked the signal board back up but I didnt screw it in all the way. I wanted for the problem to occur and then wiggled the signal board to see if the problem went away, and it did not. So that almost verifys for me that it is not a problem with the signal board. Is it worth it to remove then entire back panel and check for loose connections or anything else? What else should I look for? Is there a part that I can replace myself fairly easily? Let me know if there is anything else you would like me to try, if you need pictures of anything.

Thanks
This is almost certainly a bad bond between the flex circuit that runs from the tcon to the glass lcd panel. Some people have had limited success inserting foam to force a better contact, although this is at best a temporary patch.

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Old 08-31-2011, 05:07 PM   #19
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Default Re: Sanyo DP46848 screen half dark

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This is almost certainly a bad bond between the flex circuit that runs from the tcon to the glass lcd panel. Some people have had limited success inserting foam to force a better contact, although this is at best a temporary patch.

PlainBill
So you don't think this is a problem with the T-CON board itself? I disassembled the TV all the way and removed the T-CON board and cleaned all of the contacts on both the board and on the 4 ribbon cables, and still no change. I already had the TV put back together before I saw your post so I didnt put any foam or anything inside there. Where would I place the foam at if I do decide to take it apart again? Would it go under the ribbon cables? or above the ribbon cables between the area where it connects into the lcd panel and the top of the housing?
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Old 08-31-2011, 06:32 PM   #20
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Default Re: Sanyo DP46848 screen half dark

Quote:
Originally Posted by CamBlack View Post
So you don't think this is a problem with the T-CON board itself? I disassembled the TV all the way and removed the T-CON board and cleaned all of the contacts on both the board and on the 4 ribbon cables, and still no change. I already had the TV put back together before I saw your post so I didnt put any foam or anything inside there. Where would I place the foam at if I do decide to take it apart again? Would it go under the ribbon cables? or above the ribbon cables between the area where it connects into the lcd panel and the top of the housing?
No, it's probably not the tcon. A pair of flex conductors run from the tcon to the LCD panel, the other end of those conductors are bonded to the glass plate that makes up the active part of an lcd panel. While it is possible the problem is the tcon, it is much more likely the bond between the flex conductor and the glass panel has broken. A definitive test would be to tap the tcon and then the upper left corner of the display to see which 'fixes' the problem.

If it is the panel, you would have to put something between the panel housing and the panel frame, or inside the panel frame. Even then the cure is temporary at best.

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