Dell E153FPB Back Light problem

[MegaOne302]

Re: Dell E153FPB Back Light problem

It seems that the problem that you found is one that occurs qite often with the Dell monitors. I had one with the exact same problem and found that the PF751 fuse was blown. I replaced it with a 3 amp fuse and after an 8 hour burn in it is still working. The one thing that I found was that the brightness of the monitor was a bet diminished. But as I said it is still working. Thanks for your time and input.

I found an E153FPB last weekend on my way home, but when I plugged it in, it was DOA. After opening it up and checking things like the caps and fuses I couldn't find the problem. I totally pasted up fuse PF751 because in didn't look like a fuse; this was the first time seeing this type. The P in front means that it's a mini Pico Fuse. So Yep that was all, a bad Pico fuse PF751... I just dropped in a 2A Slow Blow from my parts box and boom, she's back to life.

Thanks all,

Joe

[brianh]

Re: Dell E153FPB Back Light problem - and another

Just wanted to report back and say that the Dell E153FPb that I repaired back in August is still going strong.

I've been so encouraged with the success that I purchased a broken LCD monitor on Craigslist for $10 and attempted to repair it for use on another PC of mine.

It's a KDS "Radius" LCD monitor with exactly the same symptoms that the Dell had.

I poked around with it for a while, looking for a blown fuse or bad caps. I re-soldered a few, but nothing helped. But suddenly it started working! I'm not sure what I did to fix it.

I have only one guess as to what I did that might have fixed it.

While re-assembling, I noticed that the inverter was attached to the metal frame with two screws. It looked like metal chassis just might come into contact with a trace on the inverter board, so I added some extra insulation (tape).

The trace was the output from the step-up transformer that went to the CCFL connector.

Maybe that's what fixed it. I was so thrilled that it worked, that I quickly re-assembled it before I forgot how it went together.

That puts an end to the CRTs in my house, so I think I'll quit while I'm ahead.

[Joeheth1]

Re: Dell E153FPB Back Light problem

Ahhh - finally I've found the problem!!!!

After a lot of trial and error I have the CCFL lamps back on!

I won't keep you in suspense any longer... The problem was a blown fuse!

No... not the big white one, it was a little black one labeled PF751 (see previously posted photo if you're interested - it's on the right side and looks more like a rectifier diode).

I can read the letters "MS 2A" on it - so I guess that means that it's a 2 amp fuse. Someone else posted a schematic for a similar Diamond View monitor, which shows a 3 amp fuse. (ref: Inverter Schematic )

I've jumpered the fuse with an extremely fine strand of wire, and the CCFL now comes on. I'm giving it a burn-in-test right now. So far 1/2 hour and all is well.

I am, however, not willing to call it "fixed" yet - after all... Why did the fuse blow in the first place?

Sure... I plan on putting in a proper fuse, but I don't want to re-assemble it and have it blow another fuse (or worse) in a day or two.

But hey... after way too many hours on this project - at least I've got something positive!

Any thoughts?

It seems that the problem that you found is one that occurs qite often with the Dell monitors. I had one with the exact same problem and found that the PF751 fuse was blown. I replaced it with a 3 amp fuse and after an 8 hour burn in it is still working. The one thing that I found was that the brightness of the monitor was a bet diminished. But as I said it is still working. Thanks for your time and input.

[arneson]

Re: Dell E153FPB Back Light problem

I'm working on and off on two of these that are loseing the 5707's, and two that are loseing the smaller SMC versions of those switches.
That's four monitors and all have lost the top tube section.
The bottom tubes light on all of these and it's only the tops going out.
My question is if it's possible that the top of the lcd screens get hotter and lessen the life of the tubes?
Or because the tube connections go to the top tube, that section of inverter is higher on the board and the top inverter circuit gets hotter?
Whichever, I have found it's likely for the upper one to short the drivers.

[brianh]

Re: Dell E153FPB Back Light problem

Ahhh - finally I've found the problem!!!!

After a lot of trial and error I have the CCFL lamps back on!

I won't keep you in suspense any longer... The problem was a blown fuse!

No... not the big white one, it was a little black one labeled PF751 (see previously posted photo if you're interested - it's on the right side and looks more like a rectifier diode).

I can read the letters "MS 2A" on it - so I guess that means that it's a 2 amp fuse. Someone else posted a schematic for a similar Diamond View monitor, which shows a 3 amp fuse. (ref: Inverter Schematic )

I've jumpered the fuse with an extremely fine strand of wire, and the CCFL now comes on. I'm giving it a burn-in-test right now. So far 1/2 hour and all is well.

I am, however, not willing to call it "fixed" yet - after all... Why did the fuse blow in the first place?

Sure... I plan on putting in a proper fuse, but I don't want to re-assemble it and have it blow another fuse (or worse) in a day or two.

But hey... after way too many hours on this project - at least I've got something positive!

Any thoughts?

[arneson]

Re: Dell E153FPB Back Light problem

It's interesting that the parts stuffer eliminated C771 and 772,
and in place of C790 and R770 theres a jump, as well as C791 and R741.
I guess that adds up to 37 cents in design savings.

[kc8adu]

Re: Dell E153FPB Back Light problem

replace the 5707's and the fu9 something mosfets.
resolder all pins of the transformers and anything else that looks cracked.the 5707 subs for the 5706.

[brianh]

Re: Dell E153FPB Back Light problem

I inherited a defective Dell E153FPb. It has a defective backlighting.
I tested the bulbs in another LCD, and they are good, so it must be
a problem with the inverter. I've been reading another thread on this
site about the Dell E172fpb.
https://www.badcaps.net/forum/showth...3&page=1&pp=20
Both have Benq inverter boards and both are plagued with
similar backlight failures.

The partnumbers for the transistors are slightly different.
The C5706 are used on my board, whereas the E172fpb uses
C5707.

I've temporarily removed the 4 transistors. Three measured
Hfe=385, but one of them had an Hfe of 447 which is a bit
on the high side. Someone suggested that high Hfe was one
failure mode. But if so, why does the other lamp not light up?

The symptoms are that the lamps flick on for only a fraction of second
when the power is turned on, this is no doubt due to the initial
high voltage spike used to start the CCFL bulbs, but there is not
enough voltage to keep them going.

The flashlight test shows that the display is there - just no backlight.

I've checked the board visually and see no signs of heat related
damage, no bulging capacitors and no bad solder joints. I've
re-soldered the critical transformer and transistor connections,
but it was no help.

If I only had a schematic...

Any suggestions?

[Ihfreak]

Re: Dell E153FPB Back Light problem

I guess no one has ever seen this problem before?

[Ihfreak]

Re: Dell E153FPB Back Light problem

I figured someone here has had to run into the same Power inverter board with the same problem before. I was just wondering what other people have tried so I get an idea of which ones to test. It would give me the ability to do it on my lunch hour at work where I have all the proper equipment to remove and test them. As at home I do not. I cant do them on company time thats all..

Just trying to narrow my search down.

Thanks.
Dan

[willawake]

Re: Dell E153FPB Back Light problem

why dont you test them all? check the caps out too....

[Ihfreak]

Re: Dell E153FPB Back Light problem

I know I could just go buy the Power/Inverter board but I dont want to spend that money on that. I could buy a new monitor for that price. I know the Benq DS-1107A is the board I need to look at but I have not Idea what Transistors to look at to replace.

Any Help would be greatful!

Thanks
Dan

[Ihfreak]

Well I have 3 Dell E153FPB LCD's that have a back light Issue. I have tried to do some research on the Transistor problem for this specific monitor but havent really come to any real good conclusion or even the specific transistors to test. I am not afraid of doing board level work at all. Thats what I do for a living but this problem stumps me a little bit.

I took one board and reflowed everything on the board. It seemed to work for about 2 hours then dropped out again.

Any one got any good suggestion on this Dell aka Benq monitor?
Thanks
Dan