No Power In BenQ T705 17″ LCD Monitor
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.
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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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...
admin
August 19, 2008 at 8:27 pm
You are welcome!
Jestine
Deogracias Haw
October 2, 2008 at 1:24 am
Yes one of the trasistor C5707 got shorted thanks for your reply
admin
October 2, 2008 at 10:08 pm
You are welcome Deo!
Jestine
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
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
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
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
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
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
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
admin
September 8, 2009 at 9:35 pm
HI Erymas,
Any voltage to inverter ic once it shutdown?
Jestine
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.
🙁
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
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!
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
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.
admin
December 16, 2010 at 12:46 am
Hi Atoya,
Good to hear that!
Jestine
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
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
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?
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