Re: Troubleshooting Benq FP757

I've read on google about hfe differences with older and newer C5707s. (the ones in the board have 350-400, and some newer ones are 150-200 sometimes) But if you say they are ok, I'll order some + some proper low-esr caps and see what happens.

Can't seem to find any 2SC5707 on future electronics or digikey. Who sells them?

Re: Troubleshooting Benq FP757

Well, you were right about the C5707s. Not 100% sure how to test them effectively, but it seems 2 of 4 are shorted right through. The other side seems fine, though I'm not 100% clear on the procedure for in-circuit transistor testing. (is there a good tutorial somewhere?)

Are there any alternatives that are better suited for this board? Or should I just stick with a C5707?

Re: Troubleshooting Benq FP757

No, the pico fuse was definitely shot. I've replaced it, but it still doesn't run. I didn't have a chance to pick up better caps though. (The guy at the store didn't know what ESR was.)

I just picked up a new multimeter (MST 2325), and will start testing the transistors. But if I can't figure this out, I already have a 12v CCFL inverter waiting to be picked up, and I'll just poke around until I find 12v and be done with it. (Or do these things take considerable power, do I need an external supply?) (hops on the benq hating wagon.)

Re: Troubleshooting Benq FP757

I have a friend who had a broken CCFL bulb, and asked him for the inverter. I was thinking of just finding 12V on this board and connecting this inverter because I was too lazy to solve the issue. But he couldn't find it, so I trudged on.

It seems benq reuses the same circuit, or at least part labeling, as I am finding many posts with different supply boards, and similarly labeled parts. One part which keeps popping up is pico-fuse PF751. I tested this fuse, and found it to be broken (reading ~5Kohms.) I cannot imagine it is a good idea...

Re: Troubleshooting Benq FP757

At this point I'm pretty sure it is the inverter, as there are 2 CCFLs on each side, and I doubt all 4 would have died at once. I'm kinda thinking of being lazy and using LEDs/a case mod light to illuminate it.

As for testing them: You can also wire them to laptop/other desktop screen, no need to go out and buy a case light.

Re: Troubleshooting Benq FP757

Thanks for that.
1) I know about the good + bad lists. I wrote most of them down on my list of caps to buy, but the store only stocked one brand. And just because the cap isn't highly recommended, doesn't mean it is going to fail. Also, even bad caps will last for a certain while.

2) Everything was replaced with the same voltage rating or better, and same capacitance value. (I replaced some 10V with 16V cause I was lazy, but I cannot imagine any harm done there.) I did not have the foresight to check if any were special (eg: low...

Re: Troubleshooting Benq FP757

[could not find edit button]
After turning off my lights, and shining my flashlight at a specific angle, I noticed the screen is working, so the backlight/inverter is indeed the problem.

But the question remains: How do I test the inverter circuit? How do I test the bulbs themselves?

[Edit] This post has edit button, but not first post... why is that?

Hi, I've been reading the forums for a little while now, and finally got around to re-capping my monitor. It is a Benq FP757, and originally would quickly blink the BenQ logo dimmly, then display nothing, and the power light would go from blue to blinking orange (standby?) after a few seconds. Also, it made a high-pitched noise when off. The inverter + general power supply are one board on this unit. I recapped all the electrolytic caps, even though none were visibly defective (but I have no ESR/cap meter so no way to test, just replaced all 19).

Now, the backlight does not work...