Dell E153FPB Back Light problem

[josh_zedlav]

Re: Dell E153FPB Back Light problem

Hi Folks I'm New here I need help regarding may Dell E153FB.. I've been working on my monitor for almost 3 days.. I tried all i have read from this forum like changing the 4 transistors, resoldering the transformers and other components, and changing the fuse.. It's just that it still keep on turning on and off.. Any possible solution you can give guys? thanks in advance

[PlainBill]

Re: Dell E153FPB Back Light problem

Hello, thanks i solved the problem by just entirety de-soldering the two transformers you mentioned and re-soldering them again.

i will be watching it for a day or two

thanks

Cool!!! You might also consider buying a lottery ticket. You might get lucky twice. Not only was the problem easy to fix, but nothing was damaged.

PlainBill

[coolcurrent]

Re: Dell E153FPB Back Light problem

Good grief, couldn't you make it smaller? Fortunately I was able to match it to a real picture.

Large blue circles - transformers with bad solder joints. Remove as much solder as possible from the pins and resolder

Red circles - bipolar transistors (2SC5706 or 5707). Test and replace both if either transistor in a pair is shorted.

Small blue circles - FET transistors, one for each pair of bipolar transistors. Sometimes fail when the bipolar transistors fail. Test and replace if shorted.

Yellow circle. Picofuse. Test and replace if open.

PlainBill

Hello, thanks i solved the problem by just entirety de-soldering the two transformers you mentioned and re-soldering them again.

i will be watching it for a day or two

thanks

[coolcurrent]

Re: Dell E153FPB Back Light problem

thanks for the fast response, i'll do my homework and give feed back tomorrow.

without a sucker, which method is best for removing components with a soldering iron, i presently use brush with trimmed tips, but the brush seems to go bad quickly after few uses

[alexanna]

Re: Dell E153FPB Back Light problem

The2 gray capacitors in the area of PlainBills Red circles are known for poor solder joints also. If you gently wiggle them sometimes you will see the solder move.
Al.

[PlainBill]

Re: Dell E153FPB Back Light problem

Here is the board picture

Good grief, couldn't you make it smaller? Fortunately I was able to match it to a real picture.

Large blue circles - transformers with bad solder joints. Remove as much solder as possible from the pins and resolder

Red circles - bipolar transistors (2SC5706 or 5707). Test and replace both if either transistor in a pair is shorted.

Small blue circles - FET transistors, one for each pair of bipolar transistors. Sometimes fail when the bipolar transistors fail. Test and replace if shorted.

Yellow circle. Picofuse. Test and replace if open.

PlainBill

[smason]

Re: Dell E153FPB Back Light problem

Here is the board picture

Seems obvious to me, between reading the rest of this thread, the fact that if you whack the monitor it comes on, and from that (not terribly good) picture.

BAD SOLDER JOINTS

[coolcurrent]

Re: Dell E153FPB Back Light problem

BFD!!! I had assumed you were smart enough to post in a thread that was related to your monitor. That STILL doesn't tell me what power supply / inverter board Dell happened to use in it!!! It is easy to identify the likely defective parts by looking at the board, I know of no way to do so without opening up the monitor.

PlainBill

Here is the board picture

[PlainBill]

Re: Dell E153FPB Back Light problem

my monitor model is E153FPb

BFD!!! I had assumed you were smart enough to post in a thread that was related to your monitor. That STILL doesn't tell me what power supply / inverter board Dell happened to use in it!!! It is easy to identify the likely defective parts by looking at the board, I know of no way to do so without opening up the monitor.

PlainBill

[coolcurrent]

Re: Dell E153FPB Back Light problem

my monitor model is E153FPb. one unique thing about mine is that you have to whop the monitor on the back, then it will come on and work just fine. then after powering off for long hours, the cycle restarts again

[PlainBill]

Re: Dell E153FPB Back Light problem

Hello, my dell flat screen too has this problem. I have read the entire post, but it seems there ins't any particular solution. Can anybody point out which transistor is causing this

thanks

1. The problem is not caused by a transistor. The problem is caused by bad solder joints on the transformers.
2. There are two identical circuits for each inverter. Either (or both) transformer can have bad solder joints. Usually only one pair of transistors fail.
3. You need an ohmmeter to determine which transistors are shorted.
4. If you replace the transistors without resoldering the transformers the new transistors will also fail.
5. Several different boards were used in each model of the monitor. Without determining which version you have, it is impossible to give you a location number.
6. There are pictures of some of the different versions of the board in this thread. Since you were unable to identify which one you have, a picture of YOUR monitor will be necessary. See my signature for information on taking and attaching one.

PlainBill

[coolcurrent]

Re: Dell E153FPB Back Light problem

Hello, my dell flat screen too has this problem. I have read the entire post, but it seems there ins't any particular solution. Can anybody point out which transistor is causing this

thanks

[dell-usional]

Re: Dell E153FPB Back Light problem - and another

top fix chap, a bit of 2 amp fuse wire done the trick. all hale brian h

[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.

[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 !!

[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

[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.

[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.

[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

[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.