Dell E153FPB Back Light problem

[PlainBill]

Re: Dell E153FPB Back Light problem

I was wondering if I can use C5707 transistors for the C5706 ones, because the one on my board are C5706

As far as I know, yes. They are a higher rated version of the C5706.

PlainBill

[EGuevarae]

Re: Dell E153FPB Back Light problem

I was wondering if I can use C5707 transistors for the C5706 ones, because the one on my board are C5706

I have done it (once) and they are still working.

[Lazza]

Re: Dell E153FPB Back Light problem

Hi guys, great site.

I was given the task by a work mate to find out what was wrong with his Dell E153FPB. (Good mate...I know).

The symptom was a blank screen with a flashing on/off button. (tripping)

After looking and testing all electrolytics and fuses on the board, plus resoldering loads of dry joints to no avail, I was a little stumped.
Having searched google, I came upon this site and was immediately directed to the C5706's.
Sure enough, 2 of them were dead short. Ordered 4 from ebay and took just 1 day to arrive. Slotted them in and giving the board one final inspection, I put it back together. Low and behold it works a treat.

Thanks for the information guys.

I have a little experience with monitors and tv's so i'll be glad to help out where/if I can.

I think i'll be hanging around this site for quite a while

[johnboy183]

Re: Dell E153FPB Back Light problem

Heres a bit of info that may help in fixing this monitor. I was asked to fix one of these today with the flashing screen and green light. Replaced two of the SC5707s put it all back together and the problem was back!!
Stripped it back down and the two transistors gone again!
Just wondering what to do next when I noticed the square grey capacitor between the two transistors was wobbling! Looked with the magnifier to find both of its joints were dry and loose. Resoldered and put in two new transistors and up she ran.
Still running so hope thats a fix but it shows there are always new answers to old problems.
Cheers
Johnboy183

[PlainBill]

Re: Dell E153FPB Back Light problem

Heres a bit of info that may help in fixing this monitor. I was asked to fix one of these today with the flashing screen and green light. Replaced two of the SC5707s put it all back together and the problem was back!!
Stripped it back down and the two transistors gone again!
Just wondering what to do next when I noticed the square grey capacitor between the two transistors was wobbling! Looked with the magnifier to find both of its joints were dry and loose. Resoldered and put in two new transistors and up she ran.
Still running so hope thats a fix but it shows there are always new answers to old problems.
Cheers
Johnboy183

Good job on that one. It seems like the entire production run of Dell E153FPbs are plagued with bad solder joints in the inverter. Another point to pay close attention to is the transformers. Bad solder joints on those are often responsible for shorted transistors.

PlainBill

[Lazza]

Re: Dell E153FPB Back Light problem

Heres a bit of info that may help in fixing this monitor. I was asked to fix one of these today with the flashing screen and green light. Replaced two of the SC5707s put it all back together and the problem was back!!
Stripped it back down and the two transistors gone again!
Just wondering what to do next when I noticed the square grey capacitor between the two transistors was wobbling! Looked with the magnifier to find both of its joints were dry and loose. Resoldered and put in two new transistors and up she ran.
Still running so hope thats a fix but it shows there are always new answers to old problems.
Cheers
Johnboy183

The first thing i noticed when looking at the board was the grey cap loose.
BTW monitor still running after 3 days, looks like its sorted

[Welchs101]

Re: Dell E153FPB Back Light problem

A friend gave me a Dell E153Fpb monitor. It has the same problem that has already been discussed here. The Fuse (PF751) seems to have blown. I measured the transistors (see enclosed pic) and they seem ok but i wanted to get a 2nd opinion on my measurements.

I used the diode check feature:

Transistor A:
Emitter(Red lead)-Base(BLack lead): 0.5V
Emitter(Red lead)-Collector(BLack lead): 0.183V

Transistor B same readings as transistor A

Transistor C:
Emitter(Red lead)-Base(BLack lead): 0.499V
Emitter(Red lead)-Collector(BLack lead): 0.182V

Transistor D same readings as transistor C


Transistor E and F have markings of J598. Cant find it on the net. So i used resistor measurements between the 3 leads.

Transistor E:
Pin1(Red)-Pin2(Black): 7.61Mohm
Pin1(Red)-Pin3(Black): 25.37Kohm
Pin1(Red)-Pin2(Black): 0.493Kohm

Transistor F:
Pin1(Red)-Pin2(Black): 7.68Mohm
Pin1(Red)-Pin3(Black): 25.39Kohm
Pin1(Red)-Pin2(Black): -128Kohm


I also re-soldered the pins of the inverter transformer.

I have a spare 2A fast blowing fuse but i didnt want to put it into the board until i was reasonably sure the the mosfets were ok.........

Do you think if i have resoldered mosfets and transformers that this will fix the problem. Any think else i should do to help prevent fuse from blowing again in the future?

[Rtech]

Re: Dell E153FPB Back Light problem

I would also check Collector to Base on the four 5706/5707's,and then the associated E and F if necessary.The fuse can fail for no particular reason(maybe age...like me),and I also resolder the transformers, the grey caps behind them and the two coils behind them.

[retiredcaps]

Re: Dell E153FPB Back Light problem

I used the diode check feature:

Transistor A:
Emitter(Red lead)-Base(BLack lead): 0.5V
Emitter(Red lead)-Collector(BLack lead): 0.183V

Transistor B same readings as transistor A

Transistor C:
Emitter(Red lead)-Base(BLack lead): 0.499V
Emitter(Red lead)-Collector(BLack lead): 0.182V

Transistor D same readings as transistor C

I assume the above measurements are in circuit? I measured a similar working Benq board and I get like readings on the E-C in circuit. I get 0.177V and I know my board works.

Transistor F:
Pin1(Red)-Pin2(Black): 7.68Mohm
Pin1(Red)-Pin3(Black): 25.39Kohm
Pin1(Red)-Pin2(Black): -128Kohm

Is that a negative 128K ohm reading or a typo?

Do you think if i have resoldered mosfets and transformers that this will fix the problem. Any think else i should do to help prevent fuse from blowing again in the future?

I think resoldering all the transformer pins and the c5707s and J598 should be all you need.

PS. Great clear focused picture.

[Welchs101]

Re: Dell E153FPB Back Light problem

yes it was -128Kohm.........

thanks to all for the info!

[Welchs101]

Re: Dell E153FPB Back Light problem

i remeasured that wierd reading of -128Kohm and now i get 5MegOhm. So i may have screwed up that measurement somehow.

Anyway, thanks.

I will solder in the new fuse and let you guys know what happens.....of course i will resolder/reflow the parts you have suggested.

[retiredcaps]

Re: Dell E153FPB Back Light problem

i remeasured that wierd reading of -128Kohm and now i get 5MegOhm. So i may have screwed up that measurement somehow.

I will solder in the new fuse and let you guys know what happens.....of course i will resolder/reflow the parts you have suggested.

-128K ohm is probably from

http://www.flukecommunity.com/forums....php?t-61.html

I fixed a Benq board that just had a blown fuse. Of course, I checked all the transistors, etc, but while waiting for the part to come in, I forgot to resolder the transformer pins. After I put in the new fuse, the monitor died 24 hours later with a blown fuse.

So I resoldered the transformer pins and put in another fuse and now it works fine.

[Welchs101]

Re: Dell E153FPB Back Light problem

Well, i resoldered all the tranformer pins and the pins of the transistors.

I put the new fuse in and its working fine.

Bad thing: The only fuse i had was a 3.0A Fast blow fuse. The original fuse was 2.0A. So i will probably have to order the 2.0A fuse but for now it seems to be working.

Thanks for the info retiredcaps.

[Welchs101]

Re: Dell E153FPB Back Light problem

Just wanted to provide an update on my monitor.......its still working. If for some reason it STOPS i will post an update here.

[seh4005]

Re: Dell E153FPB Back Light problem

Testing out of circuit with MM set on Diode Check
Red probe on B and Black on C, Should read about 600
Red probe on B and Black on E, Should read about 600

I'm glad this thread is still going; I'm very new to detailed diagnosis with a multimeter. The question I have is a basic one: why should the transistors read about 600? I assume it is because 600 is the measurement that C5706's are rated to read, however I can't find that information online -- if I were to come across transistors in the future how could I figure out what number they should read?

B to C: ~493
B to E: ~531

This is the reading I get for all 4 transistors. This means the transistors are bad. Am I correct in this assumption?

Thank you

[retiredcaps]

Re: Dell E153FPB Back Light problem

why should the transistors read about 600?

B to C: ~493
B to E: ~531

This is the reading I get for all 4 transistors. This means the transistors are bad. Am I correct in this assumption?

600 means nothing without the actual unit. When using a diode test function, the unit is volts.

It is 0.600 volts or 600 mV (millivolts). A diode should test in the range of 0.4 to 0.7V. So your diodes are good.

[retiredcaps]

Re: Dell E153FPB Back Light problem

Sorry, I meant your transistors are good.

I normally test transistors for shorts by using the ohm functionality versus the diode test.

I test 1-2, 1-3, and 2-3 "in circuit". If any show less than 50 ohms, I suspect they are bad. Then I retest out of circuit to verify.

[PlainBill]

Re: Dell E153FPB Back Light problem

The situation is even murkier than retiredcaps suggests. The exact operation of the diode test varies from DMM to DMM. The big variation is in the current applied. A guideline I use is that if both transistors in a pair give similar readings, while both in the other pair give radically different readings, one pair is bad. Since ther are two more or less identical circuits, if all four read the same (and are not shorted), they are probably good.

Usually, it is very clear-cut, especially in this circuit. The Royer oscillator design depends upon two good transistors. If either fails the other will usually be destroyed, unless the fuse blows first.

PlainBill

[pb64x]

Re: Dell E153FPB Back Light problem

Hi All,
I've a Samsung SyncMaster 701N LCD monitor, the problem is that when I plug it the green light is blinking, but the screen stays black, no backlight and no image.
I've checked the voltage output on the power-inverter board and I've found 5.5Vcc and 16.5Vcc.
Boards models are:
- power/inverter = IP-35135A, MT2-17 Rev0.4 2006.02.13
- video card = MJ17AS KBN94-00689C Normal Ver:1.2EK

So, the problem could be the video card, or the backlight bulb, or the LCD ?

Thanks !!

[retiredcaps]

Re: Dell E153FPB Back Light problem

Hi All,
I've a Samsung SyncMaster 701N LCD monitor

Start a new thread since you have a different monitor.

1) Post clear focused pictures of your boards after reading

https://www.badcaps.net/forum/showthread.php?t=1868

2) Please do not post pictures inline as they slow down the loading of pages.

3) For best picture quality and clarity take your boards to a window on a sunny day, turn flash off, and use macro mode. Take a top down view of all your boards (front and back). Make sure the photo is legible so that we can read the PCB printing clearly. A shutter speed of 1/125 or faster will produce nice clear focused pictures. Try to get a photo that is 2000x2000 resolution or as close as possible.