Dell E172fpb

[DJ XtAzY]

Re: Dell E172fpb

Yes. Let me give you exact details. So I plug the cord into the board while using my extension cord switch to turn the monitor on and off. Here are the results from my observation:

The green light shuts off after 30 seconds. 50 seconds after that, that hissing noise from that area. I switch it off and wait about a minute. Turn it on and the green light lights up for 13 seconds and the hissing sound will come shorty. It green light doesnt flicker either, like it did when it first died. The only hottest component I can feel without touching is IC701, but with that huge heatsink, I assume it suppose to be hot. I compared the resistance measurement with the inverter transformer and the results is simliar to the other post #52 in earlier pages.

And let just say I find it fun repairing this thing, which is why i don't want to give up!

[PlainBill]

Re: Dell E172fpb

So I found out the hissing noise is coming from the biggest transformer (T601), or along that area. I measured the resistance of the primaries and secondaries and it seems they yield no resistance? I was measuring the voltages at the 100uf cap (biggest cap) and the voltages are at 165V. I still get 400+V at teh CCFL connection but drops to 2V after a few seconds or so. None of the trannies get hot this time, so I assume no voltage are going through them. Are those voltages normal? Am I out of luck?

165 volts is normal at the big cap if your line voltage is 120 VAC. Don't bother trying to measure the resistance of the SMPS transformer. An inverter transformer should show some resistance - probably about 1 ohm on the primary, and about 1K on the secondary.

Please clarify one thing. You indicated the green power button shuts off after about 10 seconds. Is this with signal present?

PlainBill

[DJ XtAzY]

Re: Dell E172fpb

So I found out the hissing noise is coming from the biggest transformer (T601), or along that area. I measured the resistance of the primaries and secondaries and it seems they yield no resistance? I was measuring the voltages at the 100uf cap (biggest cap) and the voltages are at 165V. I still get 400+V at teh CCFL connection but drops to 2V after a few seconds or so. None of the trannies get hot this time, so I assume no voltage are going through them. Are those voltages normal? Am I out of luck?

[PlainBill]

Re: Dell E172fpb

Hi! I attempted to repair this by replacing the 4 trannies. It worked for one day and then it died because Q759 is burnt and discolored. The other 3 is fine. So I replaced that one. When I power it up, it would light up but after about 10 seconds, it shuts off, including the green power button. While it's on I can hear a hissing sound from the board, not sure which part it is coming from. Also I measured the outputs for the backlight and it reached up to 400V??? That's not normal right? I also get no voltages at time for the 2 diodes (D751 and D761). None of the FETs are shorted from my multimeter. Fuses are fine. No bulges from any caps. Already re-soldered the transformers and other joints which i think it could be a dry-joint. Any ideas?

Use a paper or plastic tube (the paper tube from the center of a roll of paper towels would be ideal) as a sort of stethoscope to identify the source of the hissing sound. It could be a bad transformer or a loose wire to a CCFL.

PlainBill

[DJ XtAzY]

Re: Dell E172fpb

Hi! I attempted to repair this by replacing the 4 trannies. It worked for one day and then it died because Q759 is burnt and discolored. The other 3 is fine. So I replaced that one. When I power it up, it would light up but after about 10 seconds, it shuts off, including the green power button. While it's on I can hear a hissing sound from the board, not sure which part it is coming from. Also I measured the outputs for the backlight and it reached up to 400V??? That's not normal right? I also get no voltages at time for the 2 diodes (D751 and D761). None of the FETs are shorted from my multimeter. Fuses are fine. No bulges from any caps. Already re-soldered the transformers and other joints which i think it could be a dry-joint. Any ideas?

[pconn5]

Re: Dell E172fpb

I'm at school and don't have access to a multimeter right now, or really any time in the near future so I can't really do this. Also the board has breaks in the circuit so I am guessing that they voltages would be off or missing all together.

[PlainBill]

Re: Dell E172fpb

Hey, I'm new here. I have a Dell E172FPb 19" monitor with a bad psu/inverter board. I tried soldering the 4 transistors that need replacing but the traces on the board were just fried so there was no way of getting them connected. I want to try and use the monitor for a project, it just needs the display and not the back-light with it. Does anyone know/can find out what the voltages are for the 10 pins that go out to the benQ logic board? So I can use and external power source (most likely a computer psu).

Thank you for any help!!

pconn5

Why not pull the fuse that provides power to the inverter and then measure the voltages yourself?

PlainBill

[pconn5]

Re: Dell E172fpb

Hey, I'm new here. I have a Dell E172FPb 19" monitor with a bad psu/inverter board. I tried soldering the 4 transistors that need replacing but the traces on the board were just fried so there was no way of getting them connected. I want to try and use the monitor for a project, it just needs the display and not the back-light with it. Does anyone know/can find out what the voltages are for the 10 pins that go out to the benQ logic board? So I can use and external power source (most likely a computer psu).

Thank you for any help!!

pconn5

[PlainBill]

Re: Dell E172fpb

I have been reading this thread for 2 days now, I have a Dell 15" monitor I am trying to fix. I found the 3A fuse bad, replaced it and am only getting 9v to the PWM IC pin 9. The backlights come on for a few seconds and go out. When they go out the Pin 9 climbs in voltage. The Power Led stays Green. I have plugged in different CCFLs and no difference.
This is the 2 lamp version of the BENQ board.
The C5707 transistors all measure good. I have resoldered the board.

Suggestions on what to do next?

Measure the resistance of the transformer secondaries.

PlainBill

[Rogerbird1]

Re: Dell E172fpb

I have been reading this thread for 2 days now, I have a Dell 15" monitor I am trying to fix. I found the 3A fuse bad, replaced it and am only getting 9v to the PWM IC pin 9. The backlights come on for a few seconds and go out. When they go out the Pin 9 climbs in voltage. The Power Led stays Green. I have plugged in different CCFLs and no difference.
This is the 2 lamp version of the BENQ board.
The C5707 transistors all measure good. I have resoldered the board.

Suggestions on what to do next?

[whone]

Re: Dell E172fpb

Hello!

I have been reading all these pages now trying to find a solution for my broken monitor Dell E172fpt made by lite-on. The issue is that one ic placed on ic801 on the powerboard is blown up, the partnr is LTA201P or TA201P. I have been searching for schematic on the monitor and the ic, since the ic is hard to find i must find a replacement for it and therefor a datasheet on the ic.

Is there any one who can help me?

Thanks in advance.
Best regards Whone.

[EGuevarae]

Re: Dell E172fpb

OK, I am a nexperienced electronics and computer technician. A customer of mine )who is very important to my business) gave me an E172FPb to repair. The symptom was the very common on for about 2 seconds, then blank screen with the green light staying on. Power supply voltages were good, caps all looked perfect, there was a little discoloring around the output transistors and only one of the transformers. Cleaned up all the solder connections around the inverter section, replaced the driver and output transistors, and the problem persisted. After much deliberation and testing, I found that only one of the CCFL lamps was firing. (Should have checked this first......) Turned out that the top lamp section (there's two lamps in there) was cooked. When I took it apart, you could visibly notice burning around both lamp ends on one side. Replaced the lamps and the monitor runs perfectly. So, if you're having the shutdown problem after two seconds, please check your lamps!!!

More than once it has been suggested on the forum, either by PlainBill, myself and others, to test the lamps and the inverter separately to isolate the problem. Look around and you'll find references to the case mod kit used to test lamps.
But good advice to new members

[YourBrainiacs]

Re: Dell E172fpb

OK, I am a nexperienced electronics and computer technician. A customer of mine )who is very important to my business) gave me an E172FPb to repair. The symptom was the very common on for about 2 seconds, then blank screen with the green light staying on. Power supply voltages were good, caps all looked perfect, there was a little discoloring around the output transistors and only one of the transformers. Cleaned up all the solder connections around the inverter section, replaced the driver and output transistors, and the problem persisted. After much deliberation and testing, I found that only one of the CCFL lamps was firing. (Should have checked this first......) Turned out that the top lamp section (there's two lamps in there) was cooked. When I took it apart, you could visibly notice burning around both lamp ends on one side. Replaced the lamps and the monitor runs perfectly. So, if you're having the shutdown problem after two seconds, please check your lamps!!!

[PlainBill]

Re: Dell E172fpb

Hello everyone
As you can most probably see i'm a newbie here and would like to ask afew questions as i have also come under the bug of the Benq.

firstly i would like to ask, would it affect the voltage if i externally mounted the transistors on heatsinks ?
as i intend to use rather bulky TIP3055 transistors to replace the standard c5707's.
I'm not amazingly good when it comes to electronics but i presume rightly or wrongly that these will do the job.
the only other transistors i have at hand are TIC106M, TIP121 and TIP2955 but again i could be wrong, i cannot use these within the monitor as they will simply cook due to higher Voltage or Amps.

Would i also need to replace FU9024 ?
As my monitor comes on for afew seconds and simply goes black, but with the green power button

Thanks for reading
and Thanks for any responses

Mark

If you had the flu, would you ask the doctor to remove your appendix?

The 'two seconds to black' symptom indicates the transistors are probably fine. Certainly, you should at least test them before blindly replacing parts.

How are the caps? Have you resoldered the transformers? Are all CCFLs working? Are there any shorted diodes? All of these should be tested. And lastly, the problem with the Benq board was not the specs on the transistors, it was the crappy soldering on the transformers. The transistors were the victims, not the culprit.

PlainBill

[minimad5]

Re: Dell E172fpb

Hello everyone
As you can most probably see i'm a newbie here and would like to ask afew questions as i have also come under the bug of the Benq.

firstly i would like to ask, would it affect the voltage if i externally mounted the transistors on heatsinks ?
as i intend to use rather bulky TIP3055 transistors to replace the standard c5707's.
I'm not amazingly good when it comes to electronics but i presume rightly or wrongly that these will do the job.
the only other transistors i have at hand are TIC106M, TIP121 and TIP2955 but again i could be wrong, i cannot use these within the monitor as they will simply cook due to higher Voltage or Amps.

Would i also need to replace FU9024 ?
As my monitor comes on for afew seconds and simply goes black, but with the green power button

Thanks for reading
and Thanks for any responses

Mark

[EGuevarae]

Re: Dell E172fpb

Yes; you are assuming right! I just soldered some caps on a 1000watt power inverter that we overloaded. First time worked like a charm. Its this lcd power board that will not work for me no matter what I do.

The very few units I've repaired from this model, had the 2 FU's, the 4 c5707's & the fuse repaired even if they were good (some 07's dead, some not ...), had any suspicious looking solder point reflowed and the transformers were resoldered even if they looked like new.

[techbrat]

Re: Dell E172fpb

It's possible that one or both of the FU9024N transistors on the board have failed as well. If one of those fails to a short, the entire board shuts down. I don't recall how they are labelled on the board (and I'm 1400 miles away from mine), but they have the same package as the 2SC5707's.

Can I assume that you resoldered all the legs of the transformers when you replaced the transistors?

Yes; you are assuming right! I just soldered some caps on a 1000watt power inverter that we overloaded. First time worked like a charm. Its this lcd power board that will not work for me no matter what I do.

[Mohonri]

Re: Dell E172fpb

well I completely give up on this board.
if anyone wants to repair this power board give me your email or something and I'll mail it to you.

None of the caps are bad and the fuse shows continuity.

the traces lifted around the transistors and its becoming a pain to do this because it did not work. none of the transformers were making any noise or humming. But seriously. after 3 sets of transistor installs. I GIVE UP

It's possible that one or both of the FU9024N transistors on the board have failed as well. If one of those fails to a short, the entire board shuts down. I don't recall how they are labelled on the board (and I'm 1400 miles away from mine), but they have the same package as the 2SC5707's.

Can I assume that you resoldered all the legs of the transformers when you replaced the transistors?

[techbrat]

Re: Dell E172fpb

well I completely give up on this board.
if anyone wants to repair this power board give me your email or something and I'll mail it to you.

None of the caps are bad and the fuse shows continuity.

the traces lifted around the transistors and its becoming a pain to do this because it did not work. none of the transformers were making any noise or humming. But seriously. after 3 sets of transistor installs. I GIVE UP

[PlainBill]

Re: Dell E172fpb

if this picture was a little bigger and zoomed in a lot closer. I could see the detailed line tracing!

Try clicking on the thumbnail in post 120.

PlainBill