Samsung T260 turns off and on by itself

[diegus]

Hi, I was looking for information on the problem I'm having and there seems to be a lot of knowledgeable and helpful people in this board.

The monitor is a Samsung Syncmaster T260, it started doing this when it was about two years old and has been getting worse in the past three years, in the beginning it would only be sporadically, now it does it daily. The power supply is the IP-54155A.

Setup:
The monitor is either plugged via DVI to a 2007 mac mini or to a macbook via HDMI. I have 5 outlets behind the desk and the monitor is the only device that fails, no mater where I plug it.

The symptoms:

• The monitor will completely shut down sometimes after an hour, sometimes after 30 mins. The screen goes black and the led turns off. If plugged to the macbook the computer stop recognizing it.
  
• Sometimes it will turn on again by itself after a second, sometimes it would need me to "touch" the switch to turn it on. Is intermediately recognized by the macbook when it comes on.
  
• On a good day it will fail two or three times during the whole day day.
  In a bad day it will come on again almost instantly but then it will turn off a few minutes later. On a bad day it wont turn off at all after the first glitch (nor the led or the screen that is).

I have read a lot of post about the "2 sec to black" problem but those monitors don't turn off completely, just the back light.

Do you think it could be a power supply capacitor problem? The ridiculous "touch" on-off switch? Or the main logic board (in which case, there isn't much I can do).

Thanks in advance for any ideas. i have a multimeter if you need me to check something but it only have the basics: Ohmmeter, AC/DC voltage/current, transistors and diodes.

UpdateI forgot to mention that I measured the secondaries of the inverter, both windings are around 1K with very small difference between them, I don't have the exact value here.

Update 2It is a 26", I uploaded a pic of the model # and the rest of the boards:
Main logic board: it has all the ports, everything looks clean, I did a close up on the corner where the power connector comes in.
There is also a small board that manages the led, side buttons and the "touch" sensor.

The pictures: The board was this clean when I took it out. I don't see bulging on the caps and the pcb around the high tension components is not brown or toasted. Is one of the cleanest board I have seen.

[bammbammfran]

Re: Samsung T260 turns off and on by itself

Seems this is a 26" so it may have a t-con board besides the main and power supply
Can you post a picture of the entire back ?

PS: nice pictures !!

[diegus]

Re: Samsung T260 turns off and on by itself

bammbammfran, thanks for the reply.

I updated the original post with the info you requested.

I'm not sure yet how the touch sensor works, but I have been thinking if maybe it has some kind of "leak" issue. It has to be capacitive probably so maybe is sending false signals to the power board.

Samsung has made testing this monitor really difficult, there is no way to use it without the back cover on since the boards are not attached to anything.

[bammbammfran]

Re: Samsung T260 turns off and on by itself

OK thanks
It does not have a separate t-con, the board at the top of the screen is permanently attached and serves that purpose
I am also surprised that they went with what looks like conventional bulbs on this size screen. Most monitors I work on switch to rear lit backlight on the 24" and up
And since they are that way and that long, they could be posing issues.

It obviously has overheating issues
one way to check that is to run it open and or with the boards loose which is a bit tricky to do on these layouts
do you have any plastic zip ties ? sting could work too
What you would do is cut a decently thick piece of cardboard the almost the width of the screen and from the bottom to about where the wide ribbon plugs into the screens panel
then layout the boards on that and mark some of the screw holes so that you can tie the boards to the cardboard for stability. I have done this with tape alone but sometime the tape lets loose and boards slide.
then tape the cardboard to the screens back so that the bottoms are flush
then you can set the monitor on a non-slip surface and what I do is use something like the center cardboard of household saran wrap as a kick stand to the top of the face of the screen to stand it up so that I can run it and see what is going on. It actually does not have to be held up more than a couple inches (just enough to not trap heat on the screens face.)
Then see if it runs longer.

If it does run for quite a while longer
then you can do a start again with it cold, and try to heat one board at a time to see which board might be causing the issue.

if it doesn't run quite a bit longer, then it may be a bulb

[jetadm123]

Re: Samsung T260 turns off and on by itself

I suggest you measure the voltages at the the power supply wiring harness while the monitor is working properly and again when it goes dark. It looks like there is a legend on the side of the harness which identifies the function of each wire. Photos are good, but for the record, straight down photos are preferred, so that members can read all the writing and see all the components on each board. And yes, it could be the "touch" button as they are more trouble than they're worth.

[diegus]

Re: Samsung T260 turns off and on by itself

Thanks for the replys.

bammbammfran: I'm going to try setting it up that way, let it play a movie while I work and timing how long until it it fails.
Do you suggest heating the boards with a hair drier one at a time? I don't own a hot air gun, but also that might be too much heat too.

jetadm123: thanks for the suggestion, I will change some of the pictures and take measurements when I get to make it work open.

What I have found is that if you disconnect the touch button the screen will go off immediately and there would be a clicking noise coming from the power board, so next time it fails I will also check for the presence of such noise.

[diegus]

Re: Samsung T260 turns off and on by itself

Sorry for the double post... slow connection.

[bammbammfran]

Re: Samsung T260 turns off and on by itself

most hair dryers can get pretty hot and will work
Yes, One board at a time
you can make a bent cardboard shield to try to keep the heat in certain places

on the power button board
did you try unplugging the power cord to simulate a brown out and then unplugging the power button and then plugging the power cord right back in ?
Some units will power back on automatically after a short power out

[diegus]

Re: Samsung T260 turns off and on by itself

bammbammfran: I just tried as you suggested
- Pull the power cord, put it back in, the monitor powered back on automatically.
- Pull the power cord, disconnected the touch button, plug the power cord, monitor wont start up and also, not clicking noise from the power board.

Applied the hair drier to each board for several minutes and nothing happened. The heat sinks that were warm to the touch got pretty hot (more than I felt comfortable I must say). I used a thick envelope (is what I had at hand) as a heat shield.

- Applied the hair drier to the touch button from the back (the side you can see in the pictures) and the monitor goes off after 15 seconds. Then it wont respond to touch for 5 to 10 seconds. I had the same result 4 times (with enough time between each try to cool it down). Also after the fourth try, when I got it to turn back on by touching it, it power cycle by it self almost immediately.

In this case I used the "heat shield" to protect the corner of the screen where the lamp is but this part still got some hot air, so I would try removing the touch button board from the frame and heating it again away from the lamp.

Has been running for 80 min now and haven't failed by itself, I guess that's for having the back cover off. Will let it finish this video (155min) and continue tomorrow since is midnight here.

Thanks for the help you are both providing.

[bammbammfran]

Re: Samsung T260 turns off and on by itself

sounds like progress

[diegus]

Re: Samsung T260 turns off and on by itself

Last update of the night

I took a look under the white bezel and the touch button seems to be glued to the frame, tried to pry it away with the spudger but could not find the slightest separation.

If anyone have any idea how to remove it, I haven't found anything in google yet.

[Maverick Wolfe]

Re: Samsung T260 turns off and on by itself

This might sound crazy, but have you tried the spudger and a hair dryer? I've had to use a hairdryer to loose stuff that was glued on, once I even had to as in a forum post I read many years ago heat up a heatsink with the hairdryer to get it to let loose enough to gently twist and pull off and out of the board.. that was a rather nerve racking experience.

[bammbammfran]

Re: Samsung T260 turns off and on by itself

heating it can sometimes help release the double faced tape
heat the front side of the front trim till you feel the heat from the rear getting pretty warm on your fingers
you might have the get it started with something pointy like the tip of an exacto knife since these are sometimes sitting down inside a channel.
then do the rest with something more flat and plastic like a credit card

[diegus]

Re: Samsung T260 turns off and on by itself

Thanks both for your suggestions, heat might work, don't know why I didn't think of that if it also works for cellphone screens.

Before continuing I will check if the part can be replaced and the price, just in case anything goes awry.

Getting parts from overseas here in Argentina had become quite difficult under the actual laws and I don't want to go from a working monitor with an issue to a non-working one.

[jetadm123]

Re: Samsung T260 turns off and on by itself

If it turns out to be the touch button, it's highly unlikely you'll find a replacement through Samsung, unless you can find a used one on eBay. Perhaps bypassing the touch button where the monitor's is always on?

[bammbammfran]

Re: Samsung T260 turns off and on by itself

looks like that power button goes to the power supply which is an odd place for a touch button to go ??
can you post a few pictures of that area from both sides of the board

[bammbammfran]

Re: Samsung T260 turns off and on by itself

NO need for those pics
I managed to track them down to the larger connector.
they just travel trough the power supply

see if you have voltage on key 1 and key 2 pins with that plug unplugged
the ground pin is the first pin and is marked for testing

[diegus]

Re: Samsung T260 turns off and on by itself

Wow bammbammfran, you are really good at following tracks. Sorry the boards wheren't completely flat when I took them, the flash would have made a mess.

I'm at work not but will do the measurements tonight, hopefully I will have the time.

jetadm123: If that turns to be the case I would have to look into a way to add a switch to turn the power supply on and off. I have no idea yet if it works like a computer power supply when connecting a pin to ground starts it up or it needs some kind of pulse, etc.

Found nothing on line about the part, nor a broken monitor for spare parts, but I might have more luck if I get to see a part number on it.

Here are the last two pictures I took last night.

[bammbammfran]

Re: Samsung T260 turns off and on by itself

That square black chip in the center of that board is probably what is overheating.
let me know on those voltages
do those other wires go to a remote control board ? if they do, does that turn it on and off ?

[diegus]

Re: Samsung T260 turns off and on by itself

Hello again and sorry for the lack of updates, had a very long work day yesterday. I have the day off tomorrow so hopefully will have enough time to find a solution for this.

The cables come from another board that has five or six buttons in them for menu/input/brightness/etc (no shutdown). I guess the chip reads the buttons and send digital signals to the main board.

I'm thinking there is no way that chip can generate enough heat on itself to fail, if that is the problem indeed, so the heat should come form the lamps. In that case I'm thinking about adding some kind of insulation over the touch button. Opening a vent in the case with the dremel might work too, but I will try to solve it in a more "aesthetic way first".

Thanks to all for your time.