Benq t720 - 0 seconds to black

[budm]

Re: Benq t720 - 0 seconds to black

Well, I see on the video, you hit the power switch, the LED turns green and then the screen lights up with BENQ on the screen, then the screen turns dark and flicker back on for seconds and goes black again and but the green LED is still on solid during all these times. If it is startup cap, the power supply would have cycle off and the LED would have blink.
I also notice that the bottom left of the screen is not as bright as the right side. I still suspect the lamps or the inverter problem.

[selldoor]

Re: Benq t720 - 0 seconds to black

I have also been looking again at the video it is as you say also I have paused it and
the bottom left also looks a bit pink ( another sign of a faulty bulb)- well does to me though I dont know what the Benq start screen looks like.
I did have a monitor that did this once and took me two or three goes at reflowing the inverter joints to get it going.

If you dont have spare bulbs perhaps try changing the leads from bulb to bulb - that is to say change the leads around on the power board swap the tow at the top in your picture for the two at the bottom.

[budm]

Re: Benq t720 - 0 seconds to black

Or make two of these test lamps.

[selldoor]

Re: Benq t720 - 0 seconds to black

Yes - he means these:
Inverter testing using old CFL:
https://www.badcaps.net/forum/showthr...er+testing+cfl

[guirnab]

Re: Benq t720 - 0 seconds to black

I tried to turn it on again (with PC connected). Something is not right. If I remember correctly, the Benq logo sould dissapear right away. It seems to me that its there for too long now.

Btw, its not perfectly visible on the video, but the second "flash" is brighter than the first one...

And after the second "flash" I think it's not displaying any image (from PC). I tried to shine a flashlight on it while moving notepad window (that worked before )

Well, I have here another LCD monitor (LG Flatron L206WU). Do you think I could connect the lamps to it and its lamps to the Benq board to cross check it? I don't know if it is "compatible" - I don't want to break another monitor

[Lumberjack777]

Re: Benq t720 - 0 seconds to black

As long as the lamps are about the same size, or a little longer, it won't hurt anything. Just make sure the thick wire, and the thin wire, are the same where you plug it in, as the original lamps.

I'd maybe recheck those 4 transistors (c5707) and the 2 mosfets because that's been the case in 99% of those Benq's I repaired. Once the transistor shorts, it takes out the fuse with it. But it wouldn't hurt to check the lamps I suppose.

[Agent24]

Re: Benq t720 - 0 seconds to black

Could very well be the lamps.

If you have another inverter you can test the lamps on that, too. Pink tint or flickering and they're bad for sure.