Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Mjolinor on November 17, 2012,14:01:18
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Stand by is OK, touching the button makes the standby LED flash 6 times then go out, the TV comes on OK (audio works), the backlight comes on for about 2 seconds then goes out. This happens before the picture so it is jsut a black screen but hte colour seems OK, nice and white, not pink.
I have done the PSU 4x1000uf caps and checked the 47uf, they seem OK. There are not a lot of caps in this thing anyway. I am now thinking it is possibly overcurrent on the CFLs, no evidence for this yet as the goddam PSU will not work unless all it's earth points are connected :(
Does anyone have the correct manual, I have found several that are close with the same circuit but component designations do not match, that makes it really hard.
TV is only 2 years old so the normal age related failures do not seem to apply, can't see any dry joints but I have redone a rake of them anyway.
Any other suggestions, I really feel it should be an easy fix, the TV is very clean and doesn't look to have had a lot of use.
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Bit more info.
The tubes are controlled by a LX6503A. The datasheet I cannot find, have to ask teh maker for it and that usually means spam for ever. It has two inputs VSNS and ISNS. I disabled hte VSNS input and it works fine << was expecting rather more of a bang than a working TV but sometimes one wins.
The schematic I am using is for the BN44-00340B and it shows two sources for this signal, I think my TV only has one source and htat is driven from the 5.3 volt line so from that I figure that 5.3 votl input will enable the outputs but I broke the track so the pin is only pulled down thourgh a 100 k resistor adn hte TV works fine.
This is confusing.
Does anyone have hte datasheet for the LX6503A, I can only find a two pager that is a block diagram sort fo thing.
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So having got it working with the V sense feedback disabled it is now apparent that I have one dim tube on the backlight, as usual, sods law dictates that it is the one in the middle of the screen and it drives me nuts. It isn't too noticeable until the camera does a vertical pan or the screen has uniform colour on it.
I checked all the driving circuits and they seem fine so I think it must be a tube that is faulty.
Any suggestions other than replace the tube, they are horrible to replace and I usually end up breaking them. I have never done that on a 40 inch but I found 32 inch to be onerous enough to be honest.
Is it possible to over drive that one or under drive the rest, the TV has plenty of brightness generally.
What's the long term prognosis? Is it going to pack up completely or is it likely to work for a reasonable length of time?
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hi
wy not move the tube to top or bottom or replace tube with new one
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Well I've never done a 40 but I have done some 32s and they were awful. Do you reckon it's feasable to swap the location? I am very reticent to go that far with it, I usually end up with some crud in there and it annoys me for ever even if I am successful. :)
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hi take your time if the plastic clips feel brettel warm them with a hairdryer
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Do you know if they slide out from one end or do I need access to both ends of the tube?
I think if I search I can find a new replacement but will one new tube stand out, was thinking to put the dim one in the bottom but that means taking two out.