Hi I have a BENQ FP731 Q7T3 17" TFT, green LED comes on but Lamps do not come on, has a componet at position PF 751 is it marked > bel MS 3A, is this a fuse?, also any idea of the problems these monitors have of Schematics?

Regards

Peek

BENQ HAS A BAD DESIGN OF THE HIGH VOLTAGE BACKLIGHT SUPPLY.

YOU WILL NEED TO REPLACE A FUSE (MS 3AMP) AND FIND A BAD TRANSISTOR(IT WILL BE SHORTED)CLOSE TO TRANSFORMERS AT HIGH VOLTAGE CONNECTORS. IN SAME CASES YOU WILL NEED TO REWIND A TRANSFORMER IN CIRCUITRY OF FAILED TRANSISTOR.

REGARDS.

Thanks for the message, i replaced the fuse and monitior is now OK, do you reccomend replacing the transistors you mentioned in your post?. Also OSD is nice and sharp, but the image from the pc is slightly blurred, PC GFX card & refresh rate is ok, have reset all monitor options and set sharpnes on the OSD, no matter what i do, image is still blurred, is there an adjustment on the PCB or any component that can be causing this?

Regards

Paul

ONCE FUSE FAILED, YOUR HIGH VOLTAGE BACKLIGHT SUPPLY MAY HAVE AN INTERMITTENT PROBLEM. PLEASE CHECK FOLLOWING COMPONENTS:

ARCING IN TRANSFORMER(T751 - T754)
BAD CAP ( C734-C737, C754-C757)
BAD TRANSISTOR (Q759, Q760, Q739, Q740)

REGARDS,

SERGIY

Sergiy,

Your information about this monitor has been a big help to me. I have two of them and I was quite unhappy when one developed the identicle symptoms as PEEK had in his original post here after just 22 months of service.

I took the monitor apart and found that fuse MS 3a(PF751) was open.

I have these questions:

1. Can Q759, 760, 739 and 740 be checked without removing from the PCB using a digital multimeter to determine if one is shorted? If so, how?

2. Do you have a standard transister part number for Q759, 760, 739 and 740? Are they PNP or NPN? I'd like to order a few with the MS3a fuse.

3. When transformers T751-754 arc, do they typically have tell-tale signs that are visible? All parts on the PCB physically look good - no signs of smoke, heat, leaking etc.

4. When caps C734, 737, 754, 757 fail, do they typically short or open? Are failure of these caps common?


Thanks for your time and your help,

John

Hello I have the same Benq Monitor and I’m having the same problem, the green LED works but the display will not show up. I have been able to locate all the parts that have been mentioned in the above post with the exception of the Fuse. Were is it???

The fuse is near power supply diode heatsink.It's a 3A slow blow fuse either black if it's bel of yellow if it's littlefuse.Generally Inverter transistors 2SC5707 fail due to dry solder of Inverter transformer.Resolder all the Inverter transformers and replace all the 4 transistors if you want reliability.

I have the same monitor, the green light comes on and stays on but there is no picture. Is it just the fuse or I have to look at more components?
Please help.
TIA

the fuse and check the transistors near CCFL trafos

in my case it was 1 of the Inverter transistors 2SC5707

I have a Benq Q7T3 also. Recently it expelled a large quantity of smoke The power/inverter board has multiple components that show serious heat damage...PF751...Q759...Q760...C755...T753...and the PCB is even damaged under Q760. I have been searching the net for a place to buy a replacement board (part# DS 1107A), but have had no luck. I found a few retailers selling DS 1107A's (made by BenQ) but they are for Dell monitors. I would think that they would work but the plug-in for the power cord appears to be located in a slightly different location. Does anyone know where I can find the proper replacement board.
Thank you for your time and any suggestions.