LCD TV/Monitor repair help

[G. Hoffman]

The Toshiba 32C110U1 TV I'm using as my desktop monitor has started doing something really weird - or at least, I've never heard of it, but this is far from my area of expertise. 

The screen freezes, and then fades to black starting on in the lower right of the screen, and fading to the upper left.  The power switch also freezes, so that I can not cycle the power without unplugging the monitor.  Sometimes, I unplug and plug it back in, and things will be fine for hours, other times it immediately does the same thing again.  It seems to get more frequent with time.

Flickr link to a video.

(Sorry about the video quality - all I had was my phone, and it is unpredictable enough it was pretty hard to catch.  It does show the problem quite accurately.)

I've checked the ESR of all the power supply caps, but they are fine. I'm assuming this has nothing to do with the back light, because when I am behind the monitor to unplug it I can still see the back light through the vent holes.  There is nothing which is visibly damaged - the cables all appear to be in good shape, and the larger ones I can easily check don't show any shorts or opens; and none of the chips have any black marks or other evidence of having been particularly hot.  I've had it open three or four times, and when I do, pretty much all I can do is reseat all the connections.  I did, last time, replace a piece of tape that was holding down the cable from the main processor board to the LCD controller, as the old one had lost all adhesion.  This fixes the problem for a week or two, but then it comes back.  I use this screen a LOT, mostly for CAD/CAM work, but also for hobby schematic and PCB layout stuff, so it is VERY frustrating, but buying a new monitor is not really in the cards (as in, credit cards) at the moment. 

Any suggestions would be MUCH appreciated.


Gabriel

[tautech]

Can you run some flying leads out so you can check PSU voltages when fault occurs?
I have come across cracked solder joints in older equipment as a result of the many thermal cycles.
The problem when you remove covers etc, you change any heat build up characteristics.
Not always easy to find, but freeze spray or hot air can help.

[G. Hoffman]

Can you run some flying leads out so you can check PSU voltages when fault occurs?
I have come across cracked solder joints in older equipment as a result of the many thermal cycles.
The problem when you remove covers etc, you change any heat build up characteristics.
Not always easy to find, but freeze spray or hot air can help.

Maybe.  I'll give it a try.


Gabriel

[wraper]

Looks like software crashes. Might be bad RAM or CPU. Try to update firmware if aviable for download. If it does not help, you can attach small fan above cpu and ram, if that elimenates the problem or reduces crashes, you will know that fault is somewhere there.

[Dan_o]

looks like its loosing LVDS sync.
Check/clean the LVDS connector from the main board to the T-CON board, sometimes it's just a loose connection.

[G. Hoffman]

The difficulty in finding the problem is made much worse by the fact that, every time I open the thing up to trouble shoot, I have to unplug the cables and when I put it back together it works fine for a couple weeks.  Which is where I am right now.  I redid a couple of solder joints which looked a bit dodgy on the power supply, so it's good for the moment. 

Thank you for all the suggestions, though, and keep them coming if you have any other ideas.  As of yet, I have no clue if what I've tried has worked, but still, thanks!

[Rasz]

not main psu
also not scaler ram - you can check by moving mouse when it happens, you wont see any movement because screen is frozen

its Tcon - lvds receiver chip or one of the ceramic caps shorting

since you say it goes away after messing with the tv it sounds like a bad solder joint or cracked lvds cable