Question about Samsung SyncMaster 920NW Monitor

4 Answers

Samsung 920nw Turns on, warms up then goes off.

The samsung 920nw will turn on for a minute or two the backlight will go out. After turning it off and then turning it back on it will stay on for a few seconds.

So far I have opened it up and checked the capacitors which are not bulging or leaking. I have also checked the solder joints in the back and re-soldered a couple of them and I am still getting the same result. I would like to know any other ideas or if it is the backlight.

So if it is the backlight why can it still turn on and supply a bright white?

pictures of inverter board
http://tinypic.com/r/2eqc5jm/6
http://tinypic.com/r/j7gcjc/6

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  • 5 more comments 
  • klekampcd Jun 04, 2010

    I am still going through the troubleshooting and checking voltages I did see something I'm not entirely sure of. So here is a picture of the possible leaking cap. (well I think it's version of a cap.) It does build a current but I'm just not sure of the black on the tip.
    http://i49.tinypic.com/33xvq1k.jpg http://i48.tinypic.com/igwar5.jpg

  • klekampcd Jun 04, 2010

    With the power on the large (450v) cap. is reading 168v, from the other 4 caps you are referring to, top down they are 14.24v, 14.24v, 14.24v, 5.14v, and 5.14v. Without power on my cap and resistance setting, they give an OL. But I'm not sure If I need to remove the caps from the board to get a proper reading. I'm using a Craftsmen 82369 multi-meter, used to have a fluke meter, but it was stolen.

  • klekampcd Jun 04, 2010

    Here is a photo break down:
    http://i50.tinypic.com/5x5w0m.jpg

  • klekampcd Jun 06, 2010

    I just pulled the lamps and I'm pretty sure they are bad. I referred to your photos and they look similar.

    I hope html code works for this link instead you making you copy and paste.

    Image and video hosting by TinyPic

  • klekampcd Jun 06, 2010

    No html code here is the link:
    http://i46.tinypic.com/dq0ghy.jpg

  • klekampcd Jun 06, 2010

    I guess I should have checked this first, but I took the lamps off and ran them without the acrylic screen and they run fine. When I put them on in any direction or connection they do not want to turn on for more than a second. So I think something is going on then the metal bracket gets spread apart, probably with the wires and lamp connection. I will have to mess around with it more tomorrow.

  • klekampcd Jun 11, 2010

    Ok after look over and testing the two sets of bulbs I found the set that is bad. I looked at lcdparts and they do not carry the right bulbs. The model number is ws2ymcwgl1, they are just 19" ccfl bulbs. I was wondering I should be able to use any 19" ccfl backlight bulb correct. I was also wondering what is a decent price for two bulbs?

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Yes, it can be bad lamp assemblies (see my bad backlight album) due to poor soldering works or just worn out. You need a set of spare lamp assemblies to find out if it is the lamps or the inverter circuits, the inverter goes into shutdown mode if there are short circuits, or the lamps are drawing too much current, or the lamps do not conduct after firing voltage is applied to the lamps. You can also have open/shorts winding of the inverter transformers. One thing about the caps are that they can look OK but have high ESR. One experiment you can do is to heat up the caps using hair dryer for about 3~4 minutes then plug the monitor to the outlet and see if the lamps will stay on.
Here is the service manuals, at least you can take some voltage measurements.
http://elektrotanya.com/?q=showresult&megnev=samsung&megnev2=920nw&kategoria=&kat2=all

http://s807.photobucket.com/home/budm/allalbums
http://en.wikipedia.org/wiki/Capacitor_plague
http://www.badcaps.net

Posted on Jun 04, 2010

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  • 3 more comments 
  • Bud Martin
    Bud Martin Jun 04, 2010

    That is just a ceramic cap with black marking, that is OK. What voltages do you have on the four caps as shown in your picture next to the right of heat sink? http://tinypic.com/r/2eqc5jm/6

    Try do some comparrison reading of winding resistance reading of the inverter transfomers.

  • Bud Martin
    Bud Martin Jun 05, 2010

    OK, the large cap in the AC primary side has correct DC voltage (120v AC input X 1.414 =~169vdc) and you also getting the +5vdc for the logic board and 14vdc for the inverter circuits for the inverter circuits, your power supply is OK. At this point you need to check the resistance reading of the two inverter transformers, get the number as printed on them and go here to see if they have the pin-out of the transformers, http://www.lcdparts.net/T.aspx

    Did you dowm load the service manual? You may need to check the inverter section out, did you try using hair dryer as suggested?

    You may still have bad lamps problem.

  • Bud Martin
    Bud Martin Jun 06, 2010

    Great! you should be able to connect the lamps back on to the board and see which set of lamp does not come on, then reverse the set of the lamp connector from one set to the other, if the same set of lamp dose not come on then the problem is with that set of lamp, but if the same set of the connectors still does not make the lamp to come on then the problem is in that inverter circuits.

  • Bud Martin
    Bud Martin Jun 06, 2010

    Yes, look for cold/burnt solder joints at the end of the lamps just as shown in my bad lamps album. The Silicone sleeve may be hard to remove sometime.

  • Bud Martin
    Bud Martin Jun 12, 2010

    Are you trying to get the lamp assembly from LCDPART? They sell raw lamps that you will need to resolder the old iwres to them and it cab ne real difficult unless you have real good soldering skill. Did you look at the LCDPART instructions on how to estimate the length of the bulbs, the dia is 2mm.? I always order the raw lamps for repair, they are about $9.95 ea plus shipping, so you are talking about $30 total. You can use other lamp assembly as long as it will slide back into the screen and has the right connectors on it.

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Ok guys sry i took so long...im part off sumsung..920wn lcd monitor has a bad ht leads.so just take ur girlfriens nail polish and cover the ht cables to isolate it from the metal coverplate.the ht protection circuit is very sensitive.only 400mv lots will trips the backligts...if u got a problem find backligts then try using old scanners light with its own circiut .its uses 12v 100ma

Posted on Jul 02, 2010

  • phervey534 Apr 18, 2011

    What does ht stand for, and where are these ht leads?

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Had same problem, Monitor first turn on, backlight off after couple of minutes, off/on backlight off after few seconds.
Solution cut J503.
Found voltage OVPT (IC501,7) quite low (1.6V) this is the reference value for VSEN the over voltage value. By cutting J503, OVPT becomes 4.5 volt but is not depending anymore on the current through the lamps. Instead of the link J503 I solder 2x 1N4148 diodes which makes the OVPT not go below 2,8 volt.

Posted on Nov 13, 2011

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When I turn on my computerSamsung 920nw Turns on, warms up then goes off. - mag-glass_10x10.gif the monitor turns on for about 3-5 seconds and then goes black. The blue light stays on and does not blink. If I turn the monitor off then back on it will again show the screen for about 3-5 seconds then turn black

Posted on Oct 27, 2010

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Solution cut J503.
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