BenQ T701 problem

faulty power board... possibly caused by blown capacitors..

budged electrolytic capacitor nearby high voltage transformer. 220microcarad/25Volts. apply fresh solder and re-connect lamps.

If you can, check the display settings.
Some graphics cards have an option for dual monitors.
Sounds like the card is seeing only 'monitor 2'.
If you have more than one monitor port, try plugging both monitors in.
If no luck, you may have to boot into BIOS at power-up and configure from the menu.
But be careful not to fiddle with unknown settings in BIOS - this is the 'nerve center' of the computer and could cause total digital catastrophe.
If not sure, don't.
Or get expert to help re-configure.

Should have reset to factory settings in the display menu under settings.

see this one
http://www.fixya.com/support/t155971-benq_t701_lcd_monitor

see this post
http://www.fixya.com/support/t155971-benq_t701_lcd_monitor

I had a similar problem: the backlight on my Benq T701 only functioned for a couple of seconds every time a turned the monitor on and then the backlight switched off (sometimes in two stages). An electronics guru at work said with those symptoms the transistors rarely were the problem and I just needed to resolder the connections of the high voltage coils onto the PCB. On visual inspection those solder connections seemed ok, but when I tried to reflow the existing solder at one connection I spotted the problem: just a thin surface layer of solder was present and I had to add solder to fix the problem. The 4 coils each have 6 leads on one side and 2 on the other. I only soldered the connections on the side with 2 leads. In just 30 minutes and without buying parts the monitor is now up and running again.

if your monitor is not connected to a pc, then it cannot find a vga signal input and therefore go into power saving mode, which is indicated by the orange light, but as soon as you connect to the pc and power on the light will go green and the monitor will power up.

see this post
http://www.fixya.com/support/t155971-benq_t701_lcd_monitor

does it display a picture for a few seconds before it goes blank. or do you not get any picture?. i think i might know what it is but if you could let me know :-) All the best John