Question about Toshiba 27DF46 27" TV

Picture limited to a single pixel horizontal line, sound fine

I recently purchased a floor model (Toshiba 27DF46) at an electronics retailer. it worked fine for about 3 weeks, then started randomly losing picture to a single pixel-wide horizontal strip across the screen for a second or two then return back to normal. over the next month it was happening more and more, and now, no picture shows up, just the line of light...almost seems like the whole picture has been squashed into that one line. again the sound still functions normally. Any thoughts? thanks!

6 more comments
Anonymous Jan 24, 2008

I've had my Toshiba 27df46 for 18 months. One year ago it broke and the repair person "repaired a defective solder connection at q803 on the circuit board". This was covered under the warranty. Now I have the same problem discussed above -- a single pixel horizontal line and occasional sound problems, but I am out of warranty. My question is "are these two problems related?" Is this something that the repair person should have caught when fixing the solder at Q803? Or is it Toshiba's fault for making a defective TV? Or am I just plain unlucky?
NickMantia Feb 06, 2008

Does anyone know how to force this to happen? I'm having the same problem with my Toshiba 27DF46 27" Flat CRT TV. I have an extended warranty through Best Buy, but they will not come out unless the TV is showing the problem. Mine seems to happen randomly when watching TV, watching DVD, but I have not been able to figure out how to replicate the issue

Any help is much appreciated!

Nick
RANGERGHS Apr 25, 2008

SAME PROBLEM.....AS TIME GOES ON IT GETS WORSE. IONLY THAT HAS BEEN TRIED IS TO SHUT IT OFF AND TURN IT BACK ON AGAIN. iS THERE ANYWAY TO FIX IT WITHOUT OBTAINING AN OUTSIDE SERVICE?
Anonymous Jun 28, 2008

did you find a solutIon?

did you find a solutIon?
gwwis48 Sep 06, 2008

hi. i have a 27df-46 also. after the first week i have nothing but a thin line across the middle of the screen. please help. thanks
Ovets Jan 07, 2009

I have the same problem (intermittent collapse to horizontal line). I tried resoldering the yoke connection to the main board and tightening the yoke connector but no improvement. I suspect its the vertical amplifier.
prschu Mar 25, 2009

I have the same issue with my 27DF46. I read the above and decided to follow the suggested inspection. I did not find any cracking in the soldering, but found that, as long as I had the back of the TV off, it worked fine, but when I put it back together, it would flat-line again after a few minutes to a half hour. Over time I realized that, when the room was colder, it would not occur, but when the room warmed up, the TV would flat-line again. It occurred to me that the heat sink was likely not doing its job. I tried placing a small fan next to the TV & as long as the fan is on, there is no problem. So, I wonder if there's a way to improve the heat sink function? PS - There was (heat sink) grease between the IC and heat sink, but no screw to connect the IC to the heat sink. I tried installing a screw, but that didn't help at all.
prschu May 11, 2010

Bill,
I have the same issue with my 27DF46. I read the above and decided to
follow the suggested inspection. I did not find any cracking in the
soldering, but found that, as long as I had the back of the TV off, it
worked fine, but when I put it back together, it would flat-line again
after a few minutes to a half hour. Over time I realized that, when the
room was colder, it would not occur, but when the room warmed up, the
TV would flat-line again. It occurred to me that the heat sink was
likely not doing its job. I tried placing a small fan next to the TV
& as long as the fan is on, there is no problem. So, I wonder if
there's a way to improve the heat sink function? PS - There was (heat
sink) grease between the IC and heat sink, but no screw to connect the
IC to the heat sink. I tried installing a screw, but that didn't help
at all. Any other suggestions?

2 Answers

William Rayburn

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934 Answers

This is actuall quite a simple problem... What you have explained here is a loss of vertical deflection. By the symptoms you described, working now and not working it's most likely the the vertical IC an LA7847-E has probably become ring-cracked at the point where the pins are soldered to the pc board. Depending on how long it has been allowed to arc the IC may have failed also, but they are not terribly expensive or difficult to repair - at least not here in the shop. The main board has to be removed. Locate the vertical IC - it will be mounted to a metal heat sink and the IC will be stamped LA7847. Then turn the board over and inspect where the pins are soldered to the foil side of the board. One or more will look ring cracked or fractured all the way around the pin. At this point you have two options, carefully reflow solder over each pin and put it back together or replace the IC by de-soldering it and removing it from it's heatsink. remember to use a good heat sink grease when applying the new IC.. There should also be a couple of caps in pretty close proximity to that IC... One should be about 50v/100uf and in the shop here we test em all... You might also just replace that one for good measure - they're not expensive either... If any of this sounds too complicated take it to a reputable shop and pick it up in a day or two.. Job shouldn't be that expensive or time consuming. My record in the shop here for doing those is 15 in one day. Average cost for that set, we charge is under $100 if you bring it in and pick it up.. Hope this helps Bill If you're calling around to the repair shops you might just ask if they have that IC on-hand or if they will need to order it..

Posted on Jun 07, 2007

Ovets

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2 Answers

I had the same problem and resoldered the connections to the vertical amplifier, but it did not fix the problem. Then I looked at the thermal connection of the amplifier to the heat sink and noticed that the thermal grease only covered part of the area between the amp and the heat sink. I unscrewed the amp from the heat sink, removed the thermal grease, and then screwed the amplifier back on to the heat sink (with no grease). Now everything works fine. I will add thermal grease when I get a chance. I think that the problem was caused by a mis-application of the grease at the factory. It looks like the grease was there, but not in the right position to be effective.

Posted on Apr 10, 2009

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