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Repairing BenQ 17″ LCD Monitor
By Jestine Yong on January 31, 2008
I came across a common fault problem in BenQ 17″ LCD Monitor. The problem is have power but no display. Once you has opened the LCD cover, check the pico fuse for open circuit (very common), the push pull transistors C5707 for short circuit and the Buck royer circuit p-channel fet FQU11P06 also for short circuit too. For your information, if you can’t get the FQU11p06 you can always use FU9024N as a replacement. Resolder all the high voltage transformer pins and replace the components above and I’m sure you will bring back the life of this BenQ 17″ LCD Monitor.
You may go to this fairchild semiconductor website to download the spec of the FQU11P06 P-channel FET.
http://www.fairchildsemi.com/ds/FQ/FQU11P06.pdf
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louie
September 25, 2010 at 4:59 am
Thanks, will have to recheck again or replace all filter capacitors with branded one with low esr... I dont have esr meter and just measuring caps value (some were off by 30 to 50uF before I replace with local caps). If still the same then I guess bad news for me 🙁
Again thanks and have a good day
admin
September 25, 2010 at 9:42 pm
HI Louie,
You need an ESR meter because checking the capacitance value willmake you into believing a bad cap is good.
Jestine
louie
September 26, 2010 at 2:28 pm
No locally available ESR meter here in my country... For now it's a shotgun method for me - will buy next week low esr caps and replace all filter capacitor. I just hope my main board is not the culprit.
Thanks again 🙂
Param
October 6, 2010 at 6:56 am
I have hp 1530 monitor it goes black after 1 -2 sec.i have already replaced all 470uf (10 nos)caps and also pico fuse with a normal fuse of rating 2A.but still having same problem.In inverter circuit some more capacitor of rating 33uf and 2 47uf.i have no idea about mosfetPlease help me with pics if possible.
thanks dear
admin
October 6, 2010 at 7:45 am
HI Param,
Try check the backlight because if one of them bad, the display will shutdown.
Jestine
Param
October 8, 2010 at 4:07 am
thanks jestine,
Now i have changed one pair of c5706 and now display is stable but it is very fainted/dim.Is it possible that one of backlight got faulty.please help me to sort it out.
thanks,
Param
admin
October 8, 2010 at 9:48 am
HI PARAM,
Yes, it could be one of the backlight have problem. Make sure also there is no dry joints in the high voltage transformer.
Jestine
Param
October 9, 2010 at 12:24 am
Thanks Jestine,
Now i checked all the joints.and now i sure that one of the inverter circuit is faulty ,I have already changed the transisitor c5706(2 nos).but the problem is same.Is it possible that inductors and transformer are faulty? Or is there substitute available in market to replace one of the inverter circuit.Please help
admin
October 10, 2010 at 12:44 am
HI Param,
Always use back the same part number. In your case, a bad backlight, bad transformer or inverter circuit could cause the shutdown problem. Sometimes a bad ballast capacitor could cause this problem too.
Jestine
Dean Parry
October 11, 2010 at 1:37 pm
DGM Monitor 24" powers up fine blue flashing light with pc switched off and static blue light with pc on signal is seen by pc. Backlights are on when lightly tap screen you see bright light so i think backlight is ok.
But no picture at all? all caps looks fine no swollen or leaking?
Is this the MCU? or more simple maybe?
Kind Regards,
Dean
admin
October 11, 2010 at 9:57 pm
Hi Dean,
Yes if the backlight is good then most probably the mainboard problem. Before that you have to make sure all voltages entering the mainboard are good and stable. If the voltages are good then suspect the MCU.
Jestine
eric
October 13, 2010 at 5:50 am
HI
Jestine
I have been given BENQ Q7T4 MONITOR AND THE TRANSISTER Q805
IS SHORTED. ON THE BOARD NO MARKINGS WHAT TYPE OF TRANSISTER IS IT
WOULD BE A P CHANNEL MOSFET OR POWER MOSFET ON THE TRANSISTER IT
IS 6KDPE548 TRYED AND COULD NOT FIND WHAT TYPE IT IS.
THE BOARD IS 48.LIC02.A13
ERIC
admin
October 13, 2010 at 9:08 am
Hi Eric,
Sorry i do not have the schematic and the monitor with me thus i can't provide you with an answer. Do you mean the transistor Q805 part number is 6KDPE548?
Jestine
Hocine
October 24, 2010 at 8:08 am
Thank you ...
Kenny
October 28, 2010 at 3:06 pm
Jestine,
I have a LG 32LC2D LCD TV. I get a 5V reading on the "5V ST" pin and 0V on the "ACD" pin (ACD = AC Detect, aka PS ON).
From what I have read online, this is a PSU issue, not a main board issue. However, I do not know how to fix it. No bulged capacitors, tested capacitance in capacitors, tested Standby Transformer, Schottky diodes and many other parts and haven't found anything broken yet.
Any suggestions?
Thanks in advance
admin
October 31, 2010 at 4:12 am
HI Kenny,
Is there any other voltages measured besides 5 volt? What is the colour of the power LED? Is your problem can't turn on the tv even after pressed the on/off button?
Jestine
Kenny
October 31, 2010 at 1:54 pm
Jestine,
Thanks for your prompt response.
I get no other voltages other than 5V on both P201 5V ST pins (3 and 8). The LED is completely OFF.
However, if I put a jumper between 5V ST and ACD (AC Detect), the TV works fine and with the TV ON, I get readings on the 3.4V and 6V pins of P201. BTW, per what I have found, ACD should be an active 5V output from the PSU to the main board but for some unknown reason, on my PSU is 0.01V and I don't know how to get it fixed.
Also, if I put a jumper between 5V ST and RL-ON (Relay ON), I can hear the relay clicking.
Thanks for taking the time to help me.
admin
November 1, 2010 at 8:40 am
HI Kenny,
Have you trace backward to see any bad components at where the ACD signal was coming from?
Jestine
Kenny
November 1, 2010 at 2:21 pm
Jestine,
I have not as I am new to this.
However, I took some voltages at that opto-isolator that goes to ACD on P201 and they are:
LED side (Relay OFF) 1.05V
Transistor side (Relay OFF) 0.77V
Relay ON = Jumper between ACD and 5V ST and TV turned ON.
LED side (Relay ON) 1.18V
Transistor side (Relay ON) 0.11V
Would you like a picture of it?
Thanks,
Kenny
admin
November 2, 2010 at 4:31 am
HI Kenny,
Thanks for the test result but i need to see the photo to have a clearer picture. Please send it to jestineyong(at)electonicrepairguide.com
Jestine
mohinder
November 5, 2010 at 12:55 pm
My LCD is completely dark - I can 'just' see the desktop, but can't do anything. If I turn the LCD monitor off and then on, I get maybe 2 seconds of the desktop - not long enough to do anything.
admin
November 6, 2010 at 4:03 am
HI Mohinder,
May be one of the backlight have problem that shutdown the monitor in 2 seconds. You may also need to check if there is any bulged capacitors or not.
Jestine
Richard
November 22, 2010 at 7:20 pm
Hi Jestine,
I understand this post is actually quite old but I am having a problem with my Benq FP71E.
The screen will go on for about 2 seconds then will go black when I turn the computer on or plug the cable back in.
This problem seems to only be with the DVI port as the VGA port works fine.
What do you think the problem is?
Thanks in advance!
admin
November 23, 2010 at 7:03 am
HI Richard,
This seems to be an interesting question. VGA can work but not DVI! I have not encounter this problem before but i believe the MCU (programs) in the mainboard could be at fault.
Jestine
pala
November 28, 2010 at 2:21 pm
hi , i have 17" lcd monitor E173fpb, when power there is faint flashing on screen and power led blinking (green) , please advise .tks
admin
November 30, 2010 at 7:16 am
Hi Pala,
There must be some components have shorted in the inverter side assuming you have checked the filter capacitors. I'm not sure which version is this board and if you see there are transistors with the part number such as c5707, fqu11po6 or fu9024n then check on these transistors for short circuit.
Jestine
pala
November 30, 2010 at 9:56 am
Thanks for the info Jestine I will check
siso
December 1, 2010 at 5:06 am
Hi!
I change a pair of swollen capacitors, 4 c5707 and FU9024N and my monitor HP 1740 is working (thanks). But now, my problem is that my monitor don´t turn off, when I turn off the windows or power off on the monitor button the screen put all in white. What happen? Why my monitor don't tur off?
Thanks again!
Un saludo,
Siso
admin
December 1, 2010 at 7:53 am
HI Siso,
I'm afraid the maniboard have problem especially the MCU.
Jestine
gayan kumara
December 7, 2010 at 8:07 am
thank you jestine, it works
Lalramthanga Ngente
December 13, 2010 at 6:03 am
I would like to know that can my Benq 17" G700AD LCD be replaced or repaired. My young kid shot at it with a toy spring gun in the right top conner side and left black round mark about a tip thump size with slide broken lines. This was accompanied by the white blank line of the same black mark size along up to the bottom which shades the right side. This makes problem in the operation and disappear a bit of writings or anything else at the right side around an inch. Pliz help immediate.
admin
December 13, 2010 at 10:58 am
HI Lalramthanga,
The LCD panel have problem and need replacement.
Jestine
naresh
January 4, 2011 at 3:40 pm
no display but power indicater on
admin
January 4, 2011 at 10:36 pm
Hi Naresh,
Is there supply voltage to the inverter ic? Did you gat any ac voltage at the backlight connector?
Jestine
Jeff Smith
January 8, 2011 at 8:03 pm
Great blog. Read every comment. My problem I have a HP W2007 20" LCD made 2008. Inside appear to be Samsung. When signal is first applied I get the regular splash screen, then the OSD, then 30 seconds or so the screen will go to the No Signal prompt, and then black. Power button stays lit. Pressing power of then on restarts the whole process. All soldering and electronics appear ok. Tried on several PC's and several vidio cables. I am at a loss. I suspect now a bad vidio input card in the monitor. Thank you for any ideas.
Bichitrananda Dhal
January 10, 2011 at 12:44 am
Hi Jestine,
Thanks for ur contributions toall the techies,
Yup the story now, i have got one BENQ lcd monitor model-Q9W5, i have quite same problem like others, i.e The screen gets black after 4-5 secs, when ever u press the input button on the side ( and also any time u power on )the screen comes and goes off,
Now this time the problem is not with the power supply board , rather its with the PC/DVI interface board, can u please suggest any sollution, if so please suggest me the location of the component,
will be greatly helpful with ur support
Bichitrananda Dhal
January 10, 2011 at 1:46 am
HI,
Its FP92W
admin
January 10, 2011 at 9:57 am
Hi Jeff,
Samsung mainboard tends to have problem with the MCU. Once the program inside the MCU corrupted, it will cause this kind of symptom.
Jestine
admin
January 11, 2011 at 1:33 am
HI Dhal,
You mean the lcd complaint was display shutdown after 4-5 seconds and you have confirmed that the problem was the interface board? If there is no supply voltage to the inverter ic then yes you can suspect the interface board but if there is supply voltage to the inverter ic (after display have shutdown) then check the backlight.
Jestine
Bichitrananda Dhal
January 11, 2011 at 3:52 pm
Hi Jestine,
I have confirmed the problem, with the interface board (swaped with new board), Ihave changed the caps for the board also, please suggest
admin
January 11, 2011 at 8:03 pm
HI Dhal,
In that the case the problem mist likely be the MCU because is the MCU that sends signal to trigger the start circuit in order for the 12v dc supply to enter inverter ic. If there is no signal from this mcu then the display will shutdown. You need to replace with a new mcu that have programs in it or you need to reprogram it with a programmer.
Jestine
gogonzo
January 13, 2011 at 1:41 am
Hi....
Im sorry, are you have schematic diagram for LCD Monitor Princenton PTFVW-15 ...
Thanks Before ..
admin
January 13, 2011 at 8:37 am
HI Gogonzo,
Sorry i do not carry any schematic diagram.
Jestine
Wim
January 18, 2011 at 3:49 pm
What about the board that are original equiped the Q805 and Q812 with the GK1C1545 can i use the fu9024 ?
admin
January 19, 2011 at 9:05 am
HI Wim,
Benq came out with few different version and it is hard to tell if that part number is equivalent with FU9024N. I could not locate any data of this part number. If you have the FQU11P06 (the spec is higher than fu9024n) then i suggest that you test it out. When you turn it on then within 10 seconds or so turn it off and place your finder to see if the replacement part is hot or not. If it is not hot then proceed to on it longer. Hope this helps!
Jestine
fernando de jesus
January 21, 2011 at 6:34 pm
hello i have a problem i dont have video on my lcd model G700AD my tecnician tellme i have to replace my power supply so i need one or replace one circuit i hope you can help me please
your friend fernando bye
admin
January 22, 2011 at 2:01 am
Hi Fernando,
You can ask the technician to check if there is any output voltages from the power supply or not. If no then you can ask him to repair or replace the power supply. If there is output voltages then the power supply is good and the problem is in the mainboard.
Jestine
Dias
January 24, 2011 at 8:27 pm
Hi All,
Nice Blog!
After a Benq t720 reparation (transistors and fuse repalced). The monitor worked well during one week. Now the problem is other. After some time (10 15 minutes) the image displayed is crepy. Vertical and horizontal lines appear out of the correct place and in motion. Similar as old CRT when we put the wrong resolution.
What is your opinion?
Thanks for all.
Dias
admin
January 26, 2011 at 6:22 am
HI Dias,
If all the voltages to the mainboard and the lcd controller board are good ad stale the suspect a bad mainboard or even the lcd panel. Make sure the cable connected between the mainboard and the lcd panel is properly seated.
Jestine
Christianne
January 30, 2011 at 10:52 am
Can you help me, please. I have 17 inch AOC LCD monitor LM725. When i power on the LCD monitor back light gets on but in the few second it make black screen. I change the 4 transistor C5706 but the problem is still the same. please help!