Solved No Power Problem In HP L1706 (PX849A) LCD Monitor

By on September 8, 2008



This Monitor came in with no power problem and found the main fuse 3.15 amp open circuited. As usual one has to find out whether other components have short circuit or not before you put a new fuse and retest the set. After scanning all of the primary and some of the major components in the secondary side of power supply i could not locate any shorted components. Placing a 100 watt bulb across the fuse and noticed that the bulb dims down and the big filter capacitor voltage did not drop even though the power jack already been removed.

Since the start up resistors are going to the power IC SG5841SZ (SMD IC) I suspect that this IC could be faulty causing the filter cap voltage remain high. Finding from my spare part compartment could not locate such part number thus i use SG6841SZ SMD IC as replacement to try it out. Before i put in the new IC, i did search from the internet and compare both spec and found that both of the IC’s were not much different from each other.

So the result was the LCD Monitor power came back a life after the replacement of the SG6841SZ IC and a fuse. This HP L1706 Monitor use some of the part numbers such as :

BIT3713 (INVERTER IC), 40P03GJ (FET), 2761I (Power FET), 817B (Optoisolator IC), 1506 (Voltage regulator IC) and AZ431 (Adjustable Precision Shunt Regulator IC). Please jot down in your diary book that the SG5841SZ can be replace with SG6841SZ.

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147 Comments

  1. admin

    February 4, 2011 at 11:30 am

    HI Uros,

    Since you said the voltage was low then i suggest that you trace from this line. It could be the problem of the voltage regulator circuit that did not supply voltage to the inverter board.

    Jestine

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  2. Rafey

    March 4, 2011 at 3:41 pm

    Hi,
    I want to open the base of my monitor hp L1706, but it wont come off. I opened the screws at the back of it but it wont come out, can you help me. And if you can, link me a drawn procedure for opening the base.

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  3. admin

    March 4, 2011 at 9:08 pm

    Hi Rafey,

    Make sure the base already out and then peel off from bottom using flat metal plate. Once opened then you can peel from the side.

    Jestine

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  4. Dex

    March 15, 2011 at 11:43 pm

    Hi Jestine!
    I need your help, advice...
    During the last few days my monitor Samsung SincMaster 940N shows strange behavior at the start. It seems it needs some warm-up time. Pc starts well and goes to windows, but monitor has just blinking diode and after few minutes it I get desktop, but in lower than my resolution. Then I have to readjust it, to turn it up to highest, which I regularly use. Then it works fine, but if I turn it off over the night, I ahve same problem in the morning.
    I have doubts if problem is with monitor (longer warm up time caused by inverter problem and/or bad capacitors, or with video-adapter (card). Any ideas?
    Thanks in advance!
    D

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  5. admin

    March 16, 2011 at 11:18 am

    HI Dex,

    Sorry i don't get the meaning "but monitor has just blinking diode and after few minutes it I get desktop"- could you elaborate? What is the complain of the monitor?

    Jestine

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  6. Dex

    March 16, 2011 at 3:00 pm

    Jestine, sorry for bad description. I'll try to explain it better - when I turn on monitor and PC, first I don't have picture on the screen. It’s quite black, and power-button is blinking blue. After few minutes picture (desktop) appears in some low resolution, so I have to change it to normal working hi-res. During the work monitor doesn't make any problems, this happens only if it is cold. If I leave it on 'stand by' during the night, it didn't make this problem and worked fine from the start. I started this 'trick' 2 weeks ago.
    I am sorry again for misunderstanding that I made first.
    All the best!

    D

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  7. Dex

    March 17, 2011 at 10:56 am

    Another correction, sorry... Last night I turned off PC and left monitor on. When I turned on PC this morning monitor screen stayed black, and after about 3-4 minutes desktop appeared in its normal, high resolution. While PC was starting and booting, blue power button on monitor was blinking...
    So, it seems that if I leave monitor on when PC is not working it won't help a lot. Do you have any idea what can cause this late 'awakening'?

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  8. admin

    March 20, 2011 at 11:06 am

    HI Dex,

    It seems either the MCU in the mainboard or the crystal have problem but the chances is higher in the MCU. I came across this weird symptom in Samsung Monitor and the cause was a bad MCU.

    Jestine

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  9. admin

    March 20, 2011 at 11:07 am

    Hi Dex,

    If all the output voltages from the power supply is good then suspect bad MCU.

    Jestine

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  10. Dex

    March 20, 2011 at 12:02 pm

    Thanks a lot Jestine!
    I will measure voltages from PSU. If its about MCU, is it enough to try to buy new MCU and replace it, or there I must do something else, too?
    Btw, could be it some bad capacitor in PSU area which makes this problem. On internet I saw that those are mostly source of problems in LCD monitors. Of course, I don't doubt your knowledge and experience, just ask...
    Thanks, again!
    Dex

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  11. admin

    March 21, 2011 at 4:09 am

    HI Dex,

    If the output from the power supply is good then don't suspect the cap. As for the MCU you need to get one that has programs in it. Don't buy a blank MCU.

    Jestine

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  12. Miki

    April 1, 2011 at 3:34 am

    Hi Jestine.I have problem with LCD HP L1706.The problem is picture flickering.At resolution 1024x768 an refresh rate 60Hz,there is short horizontal flick in random area screen,back light is always on,but on 70 Hz refresh rate and higher also back light start to flicker.I checked PSU (e-caps are fine,voltage is stable).Do you have similar problem? Please help!
    Thanks

    MIKI

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  13. admin

    April 1, 2011 at 8:21 am

    HI Miki,

    Sometimes backlight always on also could have mild flick and the problem is one of the backlight may have problem since you have said that the e-caps and the power supply output voltages are good and stable.

    Jestine

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  14. hamad

    May 6, 2011 at 10:29 am

    hey guys this is my frist time to i let a comment here or a problem well first of all i have monitor LCD HP L1706 no light sometimes it works but you cannot control in the menu or in the power botton you cant do anything just you see the a message like this
    'Auto Adjustment in Progress'

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  15. admin

    May 6, 2011 at 10:01 pm

    HI Hamad,

    Most probably the the MCU in the mainboard have problem.

    Jestine

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  16. anbalagan

    May 20, 2011 at 1:05 pm

    sir
    my monitor is not working properly

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  17. admin

    May 23, 2011 at 3:25 am

    HI Anbalagan,

    May i know what is the problem and what have you replaced?

    Jestine

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  18. anbalagan

    May 31, 2011 at 12:13 am

    sir,
    No I am using the hpl1706 lcd moniter, I like this moniter very much, sir now i found some problem in this moniter, the display is not standing continiously, appear in one seconds and disappear in one seconds please give me a clear help to me

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  19. admin

    May 31, 2011 at 1:47 am

    HI Anbalagan,

    Please check for bulged filter cap, dry joints in the high voltage transformer or one of the backlight have problem.

    Jestine

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  20. Mark

    December 7, 2011 at 11:50 pm

    I have a PC Monitor(Advueu model ez17j1)and on the inside power side circuit board this white stuff is on the part(Inductor,Diode,Capacitor)what is it and do I have to replace all parts or clean it off.

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  21. admin

    December 11, 2011 at 8:21 am

    HI mark,

    If the white stuff is sort of like a rubber then it is a silicone and you can remove it if you want. it is there to prevent vibration.

    Jestine

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  22. ronaldo

    January 14, 2012 at 1:48 pm

    i have a problem with no power problem found ic 7pins #p1337. no out pls help me?

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  23. admin

    January 15, 2012 at 2:56 pm

    Hi Ronaldo,

    Is there supply voltage going to the power ic? What sort of equipment you are repairing?

    Jestine

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  24. marcelino

    March 12, 2012 at 11:24 am

    Sir, i have Philips 42" lcd the Power supply was broken i was brought in Netherlands so,where i can buy the spare parts..Power supply # 32psl3403/12-psu-3122/427-24851.
    thank you...

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    • Jestine Yong

      March 13, 2012 at 3:14 am

      HI marcelino,

      Sorry I do not know of any source in Netherlands. You can try USA website like emcompassparts dot com or try search from the list of electronics suppliers below:

      http://www.jestineyong.com/category/electronic-suppliers/

      Jestine

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  25. karik

    July 21, 2012 at 6:15 pm

    hey jestine can you tell how i can check a high votlage transformer in lcd monitor  with ringer tester ?

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    • Jestine Yong

      July 21, 2012 at 11:49 pm

      Hi Karik,

      Just place the meter at the secondary pin of the high voltage transformer. It should have few LEDs light up and you can compare the result with the other one.

      Jestine

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  26. jojogreg

    August 23, 2012 at 11:27 pm

    Hi Jestine,
    I have a friend bring me a Philips 15" LCD monitor with a problem a few secon sudden shutdown after powering up the unit.I check all the component using DMM like the schottky diode,filter capacitor,capacitor,L5991, signal diode  the transformer all found ok in the power supply section.I did not yet check the main board bec.i suspect the power section was the culprit.Can you suggest what more can i do check or it is right that i suspect only the power section?pls. advise..thank in advance..
    regards,
    jojogreg
    Philippines

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    • Jestine Yong

      August 24, 2012 at 2:00 am

      Hi Jojo,

      You need to compare the backlight with a good one because if one of the backlights failure will cause the display to shutdown.

      Jestine

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  27. systemcrack

    September 5, 2012 at 10:23 pm

    Helo Jestine,
    I'm having problem with my HP L1710 LCD monitor. When ON, a few second later the display will turn off....can u find what is the problem?
    Regards 

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    • Jestine Yong

      September 6, 2012 at 3:49 am

      Hi Systemcrack,

      It can be one of he backlights have problem, shorted high voltage transformer, bad e-caps, dry joints and also bad transistors in the inverter circuit. You really need to check that out.

      Jestine

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  28. systemcrack

    September 12, 2012 at 10:58 pm

    Hi Jestine,
    Thanks for ur reply...I have another problem with my Samsung LCD TV.The LCD TV half the screen goes black or dark when On and after an hour it will good again. I already change the MOSFET, capacitor and diode but it still having the same problem...can u give a positive input to me for that LCD TV.
    Thanks

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    • Jestine Yong

      September 14, 2012 at 9:25 pm

      Hi,

      Try check the LVDS cable and the T-con board.

      Jestine

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  29. FEJI

    October 24, 2012 at 8:54 am

    sir jestine i have an HP LCD MONITOR,  AS I TURNED ON THE POWER,  THE DISPLAY  will appear only in  30 SECONDS, though the power is on the monitor display will turn black.
    Thank you,
    Feji

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    • Jestine Yong

      October 24, 2012 at 8:39 pm

      Hi Feji,

      It could be bad backlight, bad high voltage transformer or even buldged e-cap at the secondary side of smps.

      Jestine

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  30. FEJI

    October 25, 2012 at 6:39 am

    Sir Good Day!
    How can we change if one of the backlight is defective, can we change only one light or the whole lcd?
    Thanks,
    Feji 

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    • Jestine Yong

      October 25, 2012 at 9:45 pm

      Hi Feji,

      Usually only one backlight have problem. You need a good one to compare it. You don't need to change all of them.

      Jestine

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  31. FEJI

    October 26, 2012 at 8:15 am

    A OK  THANKZ  A LOT 
     
    GOD BLESS...

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  32. mohd

    November 8, 2012 at 1:10 am

    hello sir 
      my  HCL 17" lcd Monitor is haveing no power on problem when i plugin the power cable there is no power and no led blinking are ther
    plzz help in this
    thanks 

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    • Jestine Yong

      November 8, 2012 at 8:38 pm

      Hi Mohd,

      May I know what have you checked? Is there voltage at the secondary side or totally zero volt?

      Jestine

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  33. Adabelle

    January 30, 2013 at 12:51 am

    Hello Jestine,
    On the L1706 models I continue to have a problem with blown caps. The three 10v 1000uf that are grouped together at the top of the board always go bad. I replace them using the same low ESR caps that I use for other models, but after a week to a month those same three caps go bad. My boss said that its just something wrong with the board in general and to throw those out. Is there something else on the board that is causing those to expand that can be replaced? Is there something in particular that I should look for? Thank you Jestine.

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    • Jestine Yong

      January 30, 2013 at 9:34 am

      Hi Adabelle,

      Check if the big fat filter cap in the primary side have problem or not. Next, you can replace the three 1000uf 10 volt with 1000uf 16 volt cap. Test it out and see how it goes.

      Jestine

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  34. Adabelle

    January 30, 2013 at 11:20 pm

    Thank you for the quick response Jestine! I just repaired a monitor as you advised. We will see how it holds up. Thanks again! :)

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  35. Philip

    May 18, 2013 at 7:19 pm

    Hi,

    I have this HP L1706 with a constant flickering screen. This happens when cold and stabilizes after sometime. Sometimes the screen turns bluish or reddish. I checked the capacitors and they look ok. The PSU voltages are ok. kindly assist.

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    • Jestine Yong

      May 20, 2013 at 1:12 pm

      Hi Philip,

      Make sure the cable between the mainboard and lcd panel are secured and intact.

      Jestine

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