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No Power In BenQ T705 17″ LCD Monitor

By on April 8, 2008

This BenQ T705 LCD Monitor came in with no power symptom-power LED didn’t light up. The common fault for this monitor was short circuit in C5707 push pull transistor, FQU11P06 P-channel FET, high ESR in tuning capacitor .22uf 160v, dry joints in high voltage transformer and an open pico fuse. Normally after the replacement of the above parts, the LCD Monitor would start working again but this time “No” even though all the voltages now measured normal! I began to test the SMD Volt voltage regulator and found zero volt output. A-ha! at least i know the problem is in the Mainboard.

benq t705 lcd monitor

My concentration is 100% in the Mainboard and start checking why there was no voltage from the voltage regulator. Upon close inspection, i found two pins shorted together in the Scalar IC. I took a blade and separate the two pins (leg) from shorting and i got to use a magnifier glass to help me to do the job. To my surprised the LCD Monitor starting working when the front power switch was pressed! I don’t know why the two pins can short together perhaps it could be some touch up by repair technicians from other company. The reason i say that was because i could see a scratch mark underneath the front LCD cover.

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22 Comments

  1. ucop DRPCKLIA

    August 19, 2008 at 8:20 pm

    Benq - 17" model FP71G
    hi justine remember me, i'm from klia...i also got 1 Benq - 17" model FP71G no power problem. just changed the shorted circuit C5707 and my lcd start working back. Thank you got alot of infor from u...

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  2. admin

    August 19, 2008 at 8:27 pm

    You are welcome!

    Jestine

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  3. Deogracias Haw

    October 2, 2008 at 1:24 am

    Yes one of the trasistor C5707 got shorted thanks for your reply

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  4. admin

    October 2, 2008 at 10:08 pm

    You are welcome Deo!

    Jestine

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  5. Yinman Chan

    February 11, 2009 at 6:32 am

    Hi Jestine, I have a BenQ G2110W 22" with a no power problem. Have you had any experience in fixing this particular model?

    Kind Regards

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  6. admin

    February 12, 2009 at 11:47 pm

    Hi Yinman,

    Never come across this model before. But just like any other lcd monitor when no power one have to check the fuse first and then test whether the power ic is receiving any dc voltage or not. If the fuse have problem please check also the bridge rectifier.

    Jestine

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  7. George

    February 16, 2009 at 3:40 am

    Hi I have for repair a BenQT705 ,on startup the screen flashes to 1 second green light ok .I have replaced ALL the C5707 and the high voltage caps still no joy can you help
    George

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  8. admin

    February 16, 2009 at 6:03 pm

    Hi George,

    Try check the backlight as a weak backlight could cause the display to appear for a second and then shutdown. Make sure also the output of the both top and bottom have the same AC voltage.

    Jestine

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  9. erymas

    September 8, 2009 at 4:40 am

    hi!!

    i need some help. I change all c5707 but no results. after 5 seconds the monitor shutdown.

    Kind Regards

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  10. admin

    September 8, 2009 at 10:20 am

    HI Erymas,

    It can be a bad backlight, bad fet, dry joints and also bad inverter IC.

    Jestine

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  11. erymas

    September 8, 2009 at 7:15 pm

    Hi Jestine,

    thank you, backlight ok, no dry joints fet ok .

    I think I'll give up

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  12. admin

    September 8, 2009 at 9:35 pm

    HI Erymas,

    Any voltage to inverter ic once it shutdown?

    Jestine

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  13. erymas

    September 9, 2009 at 1:57 am

    sorry Jestine,

    but I´am not an expert in the matter just a curious. i have 12 volts in pin 9 tl451a but they disappear.

    🙁

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  14. admin

    September 9, 2009 at 9:18 pm

    HI Erymas,

    If the supply voltage disappear after shutdown then suspect a bad Mainboard (if power LED still light).

    Jestine

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  15. desmond lee

    October 18, 2010 at 6:09 pm

    Hi Jestine,i have a Benq LCD model G2110w,any idea for the power ic no?cos ic already burn cant see the no..ps help.thanks!

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  16. admin

    October 19, 2010 at 9:42 pm

    HI Desmond,

    Sorry i do not have this monitor model with me otherwise i can compare it and let you know.

    Jestine

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  17. atoya

    December 15, 2010 at 10:17 am

    thank you for good article.

    i have repaired my banq t705 for replace c5707 with c2655 and reconect fuse PF801. the monitor back on track well & good no problem.

    thanks all.

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  18. admin

    December 16, 2010 at 12:46 am

    Hi Atoya,

    Good to hear that!

    Jestine

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  19. jm fernando

    September 28, 2011 at 7:16 am

    hi sir, how can i repair my chimei lcd monitor with no power. Chimei cmv 633a-c, please help me sir and thank you.

    jm fernando

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  20. admin

    September 29, 2011 at 8:33 am

    Hi Sara,

    May i know what have you check? Is there supply voltage to the power ic?

    Jestine

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  21. chongwolf

    September 5, 2015 at 1:12 pm

    Monitor model BenQ t705.The power light is flash so second then gone.must wait for15 min and try again many times.then it is got sound,like tititititi.after that the power light will flashing,the monitor got display BenQ,and you try more,the monitor done with its display.how can fix it?

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    • Jestine Yong

      September 7, 2015 at 12:10 pm

      Hi Chong,
      Check the filer caps in the secondary side. Make sure no bulged e-cap and that the output voltages are good and stable.

      Jestine

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