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Old 10-21-2008, 04:27 PM   #301
RunnerPack
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Default Re: Dell E172fpb

(Sorry, but the admin seems to like double-posts rather than nice clean edits )

Well, that didn't work, and I didn't test the transistors before I put it (mostly) back together, so I'm done messing with it for a while.

If I don't post back, assume I put it away for future repair/scavenging/sale. I will, however, NOT be throwing it away (if for no other reason than the Hg in the CCFLs). I just don't have the time/need to work on it right now.

Thanks for all your help, folks!
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Old 11-08-2008, 07:54 PM   #302
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Default Re: Dell E172fpb

I had the same problem where the screen would turn on for a second and turn off. I found one pair of transistors shorted, and just replaced that pair of the transistors with the TIP3055s. I also did a re-soldering job with the iron at 800degrees (to make sure all components got hot enough so the solder would wick properly) on all the main components in the PCB's heat-discolored area:
Transistors
Blue Caps
Transformers
HV LCD connectors

My screen works fine now. It's been working for 4 days.

Thanks everyone for the info!
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Old 11-09-2008, 12:40 AM   #303
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Default Re: Dell E172fpb

Do the TIP3055s get hot? Usually they do and are not a good or recommended replacment type. If the originals were 5707s they are not hard to get on eBay and not expensive.
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Old 11-13-2008, 01:44 AM   #304
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Default Re: Dell E172fpb

I was just given one of these screens and it was supposed to be dead with an inverter problem. Got it home, plugged it in and way and away with went. I used it for a few days with no problems then had the black out. If I powered it off and back on I would usually get the the display back first time. I blew it out and it seems to be working fine again. The amount of dust that I got out of it would be enough to make my laptop cranky. Having read the posts here I wonder if this is just a pre failure symptom of the transistors made worse but the dust/reduced airflow?

And what I found weird was when I restarted the display the logo was quite bright which I would think means the back light itself is working. I would always get something visible even when the display never came back up to show the desktop.

I haven't cracked the case yet one this one so about all I have done is do a slap test on it and check the connector for bent pins and corrosion. I'm curious if this sounds like the early stages of the transistor problems?

Dave
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Old 11-13-2008, 05:13 PM   #305
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Default Re: Dell E172fpb

I replaced the transisters, however now when I turn it on I get the backlight repeatedly flicking on for 0.1 second, a very faint "click" sound, and no LCD display. Any ideas?
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Old 11-14-2008, 08:25 PM   #306
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Default Re: Dell E172fpb

Quote:
Originally Posted by davmax
Do the TIP3055s get hot? Usually they do and are not a good or recommended replacment type. If the originals were 5707s they are not hard to get on eBay and not expensive.
I know, but I had them on-hand and was more interested with seeing if that was the only trouble with the board since the tip3055s were confirmed to work. Also I need to clear up some projects, and leaving it sit waiting for an order to come in wasn't going to help clear off the kitchen table

In any event, it's still going strong. It's being used by my daughter. If it fails again I'll replace with one better than the originals since I'll have to order something.
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Old 11-14-2008, 09:15 PM   #307
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Default Re: Dell E172fpb

Just noted that with my fault I found, that was because I'd replaced one transistor out of each pair instead of the blown pair by mistake(Note to self: Late at night isn't a good time to be doing this :P) So that's probably your cause if you have the same fault.
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Old 11-17-2008, 01:34 AM   #308
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Default Re: Dell E172fpb

Original transistor, C5707, is high hFE (200...560) and 3055 maximum is few tens! If pairs not are same class hFE, is possible saturation ferrite core. Sorry my "eglish".
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Old 11-21-2008, 04:05 AM   #309
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Default Re: Dell E172fpb

Quote:
Originally Posted by pmapa
Original transistor, C5707, is high hFE (200...560) and 3055 maximum is few tens! If pairs not are same class hFE, is possible saturation ferrite core. Sorry my "eglish".
That's why I never would have attempted subbing the 3055 for the c5707 of my own accord. However since others stated they had success and the screen has lasted for weeks (if not months), I felt confident in using the 3055s. And I won't be upset if it dies in a few months; by then I''ll hopefully have plenty of replacement parts. In any event, I'll post if the 3055s ever fail or cause a failure.
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Old 11-30-2008, 10:06 PM   #310
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Default Re: Dell E172fpb

Couldn't help but notice all the frustration going on through this tread but I can help you all with a work around to this problem that involves another lcd monitor.

In my case I have the same E172fpb monitor you all have and with that, the same back light issue too. I gave up trying to fix it by replacing the transistors that kept failing. I instead used the inverter/power board off my E193FP with a damaged display. Keep in mind these monitors are two different beasts.

Basically I just figured out with a multimeter which pins on the E172fpb display logic board were 3.3V 5.0V 12.0v and GND. Along with that I figured out which pins on the Logic Board Controlled the Inverter circuitry. Ends up that the logic board sends out 3.3v to the main power/inverter board to turn on the inverter circuitry, thus giving you control of the backlight with a totally different inverter board.

What I am aimming at here is that you can use ANY inverter/power board from ANY lcd that will work with the E172fpb's display logic board ,but has to meet the following criteria:

Supplies 5v DC
Supplies 3.3v DC
and Of Course has an available 0v Ground
Not to forget though, the inverter must be able to accept 3.3v to turn on its lamp circuit. Remember the 3.3V DC is important because that is used for the switching of the inverter Circuitry not to just only power the Logic board

With that information, I transfered and spliced the wiring from the E172fpb's logic board to the E193FP's power/inverter board and all is great now with the exception of brightness control, it is stuck at 100% no matter what setting I choose(not a big issue though )

So if anyone would like more info or to see pictures and video descriptions, just message me back here or through email. I would be more than happy to disassemble the E172fpb again to show you my project success

Did I mention that the different inverter logic board from the E193FP successfully fits in the E172fpb's chassis with little work?
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Old 12-07-2008, 09:58 PM   #311
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Default Re: Dell E172fpb

Hi all, First time poster, long time viewer.
Great site by the way, it has helped me fix one monitor already!

Ive a Benq FP737s...with the usual dead pair of transistors .
I purchased replacements from reputable ebay dealer, and I have already used some from the same batch successfully in another monitor.

However, after the replacement, the screen still didn't work.
I checked the fuse at FP751. So I jumped the duse (risky, I know) and the screen lights up and works beautifully.

However, the screen power button does not shut of the tubes, the screen displays all white when it should be off.

Does this indicate that one or both of the FU9024N's (Q743 and Q751) are shorted?

I presume so, but would appreciate clarification.

Thanks
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Old 01-06-2009, 03:48 PM   #312
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Default Re: Dell E172fpb

hey there new here but got abit of knowledge about electronic stuff n boards... but very little dat is.. ok wat i got is a E151fpb and da initial problem was white screen. i managed to fix that but now im stuck with another problem. now the power light is on while i get a picture on the screen for about 3sec and then a black screen.. i cn see the picture wen i tilt the screen and while using a light. so it indicates that the backlight isnt functioning.. now what i wanna knw is how to fix this problem.. any help would be much appreciated...

Ash
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Old 01-23-2009, 03:17 PM   #313
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Default Re: Dell E172fpb

ok new to this forum but many years of technical repair experience... I've already fixed some tft monitors...and indeed it's always the same 5707 and std10pf06... or similar but now I have one monitor that has another problem. After replacing all 4x 5707 and 2 std10's and the 5a fuse switching it on resulted in smoke and burning q812 q815 and q816.. so I resolder all pins on the transformers but again... smoke.

Where i lack knowledge is on the lamps and high voltage part. Measuring the high voltage caps shows now short circuits with a multi meter.
The lamps also do not but this means nothing does it?

Testing transformers with only a multi meter is also nice but says nothing except if there is were an open winding....

Basiccally my question is: If the failure is in a high voltage transformer, high voltage capacitor or one of the lamps how do you find out? And if it were the transformers...where do you get a new one...?

Moneywise it's not worth to buy all these parts but i would like to find out from the learning point of view...

thx for any help..
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Old 01-27-2009, 11:07 AM   #314
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Default Re: Dell E172fpb

i have an e173fpb 17" lcd with a blinking power light. the mainboard is different from the other ones i've seen on this issue. does anyone know any more about this type of board
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Old 01-27-2009, 08:58 PM   #315
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Default Re: Dell E172fpb

Some of the designs differ, but the solutions are usually related to one of these: Check the transistors on the high voltage side for shorts and check the CCFL to see if it's bad.

One of the Dell screens I have had 2 CCFLs and one was bad the other wasn't. This lcd exhibited the same symptoms.

If you need more help, post high res images of both sides of the pcb(s)
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Old 02-05-2009, 07:38 PM   #316
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Default Re: Dell E172fpb

In case anybody is still following this thread, there is some really bad info here, especially as to the substitution of transistors. dockarl suggests that almost any transistor with enough voltage/current rating will do the job. No, that is not the case. They have to be fast-switching type with low Vce SAT. That is why they get hot/blow up if you put something such as mje3055, which is meant as an audio amplifier.

There is very rarely a need to change any capacitors, unless they are obviously leaking or bulging.

The soldering is not bad; the board is of very cheap consumer grade with thin copper laminate. This is inexcusable in a device of this class. However, there is some unwritten rule that mandates this type of cheap board for all non-digital parts of even expensive equipment. This practice should be stamped out. Areas of the board that have overheated, however, should be resoldered.

The transformers NEVER go faulty. The exception to this is if they have been connected to raw DC by the shorted transistors. But the resulting burn-out will be obvious. The supply shouldn't be able to provide enough current to fry them.

This unit is a woeful piece of design, not unexpected from Benq/Acer. It's sad, but Acer used to make really good stuff but now they make POS crap just like HP/Compaq.

Lastly. the FPb means free of lead, not some of the other silly suggestions that have been made.

Last edited by freddyzdead; 02-05-2009 at 07:40 PM.. Reason: add
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Old 02-06-2009, 01:13 AM   #317
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Question Re: Dell E172fpb

Quote:
Originally Posted by ashkhn
ok wat i got is a E151fpb and da initial problem was white screen. i managed to fix that but now im stuck with another problem.
Ash
How did you fix that?
I have an E171FP with that problem and would really like to know how you fixed it,or you simply did an LCD panel swap?
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Old 02-06-2009, 02:17 AM   #318
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Default Re: Dell E172fpb

Anyone has tried this replacement?
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Old 02-08-2009, 04:25 AM   #319
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Default Re: Dell E172fpb

Hi All,

I've fixed about 5 of these monitors now, a mix of 172's and 173's, using the information on this thread.

The first one I just replaced the two transistors that had failed. The monitor worked for about a week then fizzed and reverted the the original problem. Since then I have also reflowed all the solder around the section of the board with heat marks and both sets of transformers. And, touch wood, none have failed since. Therefore from my experience the problem must be due to bad joints in that section of the board.

I would strongly recommend getting the proper replacement transistors to avoid having to hack the case. Also note there is a difference between C5707 and 2SC5707 which I learned from experience! In the UK you can get them from here ...
https://uk.farnell.com/jsp/search/pr...sp?SKU=1554597

Cheers
Rob
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Old 02-08-2009, 07:18 PM   #320
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Default Re: Dell E172fpb

Quote:
Originally Posted by joshAU
Hi all, First time poster, long time viewer.
Great site by the way, it has helped me fix one monitor already!

Ive a Benq FP737s...with the usual dead pair of transistors .
I purchased replacements from reputable ebay dealer, and I have already used some from the same batch successfully in another monitor.

However, after the replacement, the screen still didn't work.
I checked the fuse at FP751. So I jumped the duse (risky, I know) and the screen lights up and works beautifully.

However, the screen power button does not shut of the tubes, the screen displays all white when it should be off.

Does this indicate that one or both of the FU9024N's (Q743 and Q751) are shorted?
I presume so, but would appreciate clarification.

Thanks
I have that problem with other monitor. Is is possible that that (bold text) is the cause?
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