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-   -   Dell E153FPB Back Light problem (https://www.badcaps.net/forum/showthread.php?t=3360)

Ihfreak 02-19-2007 07:01 AM

Dell E153FPB Back Light problem
 
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

Ihfreak 02-20-2007 07:49 AM

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

willawake 02-20-2007 07:58 AM

Re: Dell E153FPB Back Light problem
 
why dont you test them all? check the caps out too....

Ihfreak 02-20-2007 08:38 AM

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

Ihfreak 03-13-2007 01:55 PM

Re: Dell E153FPB Back Light problem
 
I guess no one has ever seen this problem before?

brianh 08-09-2008 12:45 AM

Re: Dell E153FPB Back Light problem
 
1 Attachment(s)
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.
http://www.badcaps.net/forum/showthr...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?

kc8adu 08-09-2008 01:48 AM

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.

arneson 08-09-2008 12:23 PM

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.

brianh 08-25-2008 10:04 PM

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 08-26-2008 10:27 AM

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.

Joeheth1 01-15-2009 08:38 AM

Re: Dell E153FPB Back Light problem
 
Quote:

Originally Posted by brianh
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.

brianh 02-24-2009 03:34 PM

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.

MegaOne302 04-11-2009 01:47 AM

Re: Dell E153FPB Back Light problem
 
Quote:

Originally Posted by Joeheth1
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 couldnít find the problem. I totally pasted up fuse PF751 because in didnít look like a fuse; this was the first time seeing this type. The P in front means that itís 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, sheís back to life.

Thanks all,

Joe

MegaOne302 04-11-2009 02:03 AM

Re: Dell E153FPB Back Light problem
 
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 couldnít find the problem. I totally past up fuse PF751 because in didnít look like a fuse; this was the first time seeing this type. The P in front means that itís 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, sheís back to life.
And may I ask why you put in a 3A? If the fuse blows, thatís a good thing; it means it just saved the circuitry from frying or from burning down your house. So please tell me why you think itís ok to override a safety measure?

:bash: Hereís a thinker for you.

If a fuse/breaker blows in your house, do you say hey, it was only a 20amp? Iím going to put a 30amp in so that never happens againÖ ?

Thank god Spring Ďs coming. lol

Thanks all,

Joe

choodan007 04-15-2009 08:57 AM

Re: Dell E153FPB Back Light problem
 
HII somebody help me .i hav a dell E153FPf monitor itz one ic got burned i cant read that ic noumber also ,itz circuit noumber u580......plsss post that ic noumber if any one having that

Bobdee 04-15-2009 01:26 PM

Re: Dell E153FPB Back Light problem
 
Hello choodan0007
I have the new version E153fpf board
(inverter/power suppy/video all on one board) in front of me, cant see a u580.

If you have old version, is the part on the video board, if so post board number of that board, also picture if you can that may help in cross reference,this may help you,
there are a few good pics of old inverter/powe supply on badcaps
bob

choodan007 04-18-2009 08:24 AM

Re: Dell E153FPB Back Light problem
 
hii bobdee ...thanx 4 ur support tatz by wrong i mention ter circuit tatz actuallyn u 850.near to that SMT on power section .itz a 8 leged ic.

Bobdee 04-18-2009 09:25 AM

Re: Dell E153FPB Back Light problem
 
Quote:

Originally Posted by choodan007
hii bobdee ...thanx 4 ur support tatz by wrong i mention ter circuit tatz actuallyn u 850.near to that SMT on power section .itz a 8 leged ic.

Hello again
Your part number is SG6841S, Its a PWM controller,
A link to part may help,
http://cgi.ebay.co.uk/SG6841S-High-i...3286.m63.l1177

bob

you might want to check that mosfet and resistor by there, mine were gone

Nama 05-14-2009 10:01 PM

Re: Dell E153FPB Back Light problem
 
Yet another PF751 bad. Monitor has been on now for 3 hours with no problem. Thank you for you follow up Brianh. Jacob

Bubii 07-07-2009 07:02 PM

Re: Dell E153FPB Back Light problem
 
Hi Guys! I own Dell E153FPB and it has backlight problem. It works for a few secs and than the backlights turn off. The pictuire is there but no backlight. I did change pf751 and resoldered the transformers' contacts and it worked for about 20 mins (I tought it was fixed) and now it is just the same. I know it's easier to trow it in a trash but I spent so much time on research on this s##t...It was said that the problem might be the SG6841S High-integrated Green-mode PWM Controller but before I buy it I wanna know what you suggest. Help...Help...Plz.
Thanks.


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