Dell E172fpb

[Crasoum]

Re: Dell E172fpb

Sixpence take a flashlight to it, do you see the logo?

[alexey]

Re: Dell E172fpb

Hi everybody, I'm new to this forum. Just got a Dell 173fpb for 5$, it turns on but the backlight goes off after a second. Pretty much like the symptoms everybody have. The image is still visible with a flashlight so that should mean a faulty inverter circuit. A quick checkup revealed that Q759 and Q760 are short. Since it is difficult to perform a long lasting fix by replacing the faulty componenets, it would probably be better to use a 3rd party inverter board to power the backlights(see this link http://www.instructables.com/id/Repl...-Monitor-for-/ ). Some nice ccfl inverter boards are available on ebay for around 20$ (example item number: 110273603375). Then the whole thing could be powered by an ATX PC power supply as mentioned earlier in this thread (In case the power circuit doesnt work at all). But I have one concern: the datasheet for the panel (LM170E01) says that the lamps' operating voltage is around 650V and the starting voltage is around 1200V, while the inverter board sold on ebay has this descripltion: "Lamp voltage Max :1800V/Tye :1100V". I don't know what they mean by this, the operating voltage or the startup voltage.
Does anybody know if this would work as a long term solution?

Alexey

[Sixpence]

Re: Dell E172fpb

Crasoum, yes, I can see my desktop with a flashlight.

[Krankshaft]

Re: Dell E172fpb

The best solution is to just replace the 5707 transistors I read the guide at the link you posted and IMO its alot of work and probing. That could have been remedied by simply repairing the old inverter.

Most inverter failures are semiconductor or capacitor related and not transformer related.

Not to mention this hack job of a repair completely obliterates the brightness setting on your monitor I bet that guy forgot to mention that.

As for long term fix one theory of why the transistors fail is that the soldering on the inverter transformers is poor and resoldering all of the transformer leads will prevent a future failure.

Another theory is a fault in the inverter soft start circuit itself that manifests itself when you reboot the computer after a bios change. Davmax has some posts on that.

In any case I have never had any of my repairs fail again. I always make sure that I resolder all of the transformer pins of course.

[Crasoum]

Re: Dell E172fpb

sixpence one of your ccft/ccfl might've burn out. If one goes, sometimes it'll cut power to all of them.

[CudaDave70]

Re: Dell E172fpb

Whoopsie, I meant to type Q751 instead of Q741,Sorry bout that Chief.

[JBmtk]

Re: Dell E172fpb

I changed out the 4 transistors and now when I power up I get my desktop for about 2secs and then blackness, but the power light stays green. I know this is common for some people on this board, but what could be the problem? Maybe this happens when one of the transistors was not soldered on right?

I noticed the fuse was all white so I did a continuity test and all checks out, but is it supposed to appear white? Thanks

[JBmtk]

Re: Dell E172fpb

well, I figured out my problem above. One of the transistors I put in was faulty. You can easily test transistors with the diode voltage on a typical VOM and using google for instructions. This thread alone has about 53,000 views, so this is a typical problem for people..so I decided to take awful pictures of an awful setup.

Here is my sweeeet setup supported by a torque screwdriver nonetheless:


Always make sure that grounding pin is actually doing something just in case.


A blurry picture of what you need to do if the pads get lifted up. Basically, you can retrace the traces on the board to the next pad and simply solder a large gauge wire (large # = small size wire) joining the two. Don't underestimate the gauge part though, cause the resistance won't work out the same and bad things will happen...trust me.


The Emmiters on the 4 transistors all go to ground, so I ran a wire to the heat sink with a lot of solder around it.

Don't forget to de-solder R750 like someone pointed out earlier in this thread... I don't have the technical knowledge of why this works or if its good, but I know that keeps the transistors from overheating.

All in all, thank you for all the contributions the members of this forum made...seriously, a whole forum dedicated to troubleshooting something that 95% of the population would just throw away...pretty neat!

[arneson]

Re: Dell E172fpb

Placed an order for a dozen of the NTE2668 substitution device for the Sanyo transistors.
These are much easier to replace than the surface mount drivers.
I also ordered a repair kit for this board that someone put together.
He didn't specify what's in it but I was curious and it was cheap.

[2shae]

Re: Dell E172fpb

Could anyone help me find an alternative transistor on http://www.maplin.co.uk . its going to be a month before my replacement 2sc5707's arrive and this display is my only monitor other than a crt which is killing my eyes.

Please help me find a temporary fix

[arneson]

Re: Dell E172fpb

How many? PM me an address I'll mail some.

[sdecorme]

Re: Dell E172fpb

look at this
http://syscon.wordpress.com/2007/07/...klight-repair/

[ragzeeboy]

Re: Dell E172fpb

G'day All,I'm new to this forum but like you all I'm having trouble with a Benq Monitor and I've found a lot of ideas to help me fix this thing but the reason for this post is I noticed a few questions on capacitor values and their markings so here is chart that I hope will be a help also I recommend a led lighted magnifier from Dick Smith for around $15 for reading the really small ones it really makes life easier when you know for sure the correct value of any caps you want to replace. Cheers ragzeeboy

[arneson]

Re: Dell E172fpb

Thanx,
The numbering codes were helpful.
I'm using a dentist's lamp and a jewlers loop for medium small stuff.
Others are apparently using Tunneling Electron microscopes.

[mib*izzy*ssm]

Re: Dell E172fpb HELP!!!!

I bought 2 Dell E172FPB computers both would not power on... I took them apart and went through them step by step removing the components trying to see what was wrong with them.... When i remove the ribbon cable that goes to the lcd screen the back light comes on and is nice and bright. When i put it back on i get no power.. Is that the video card? I tried both video cards from both monitors and they both did the same thing...also tried both screens. Any suggestions? Thank you very much.

[Chema]

Re: Dell E172fpb

Hi everybody, I'm new to this forum, and want to share my experience with the Dell E173FPb of my daughter.
One day she call me, saying that the monitor has broken, the symptoms: no image, and blinking the power led. The monitor turns on, but the backlight goes off after one second. Pretty much like the symptoms everybody have.
I search in the WEB, and found several entries about Dell E172FPb and E173FPb with similar symptoms, and take the decision to inspect inside, following this two links:
and http://lcdpartsandrepair.com/E172fpbvideo.html
Then disassemble transistors Q739, Q740, Q759, and Q760 and with the help of http://www.kpsec.freeuk.com/components/tran.htm test it, and found that one of them is in short.
Test also the fuse BEL 3A ms 125v (PF751) but is O.K. and the two FU9024N who are very dificult to test. and decide to buy the set of:
4 x 2sc5707
2 x FU9024N
1 x BEL 3A ms 125V
from ebay, the seller "exxpressparts", in this link: http://shop.ebay.com/&_C5707+FUSE+FU9024N
When the replacements parts arrive, I test the new parts and take note how the new transistors measure with the DDM.
I change two C5707 (the pair who I look that one is in short), and test the monitor. And I have the same symptoms.
Again disassemble the PCB, and test again the transistors C5707 and all are good, test the fuse PF751 and is blow, and one FU9024N is in short.
I change the the fuse and the Fu9024N, and test the monitor, the test fail again, image 2 seconds, and black LCD, but the led power don't blink.
Disassemble the PCB, and test again the transistors C5707 and all are good, test the fuse, is good, and the two FU9024N are good.
Resolder the four high voltage transformers, and all that I can't see well weld. AND the SAME, after one second no image.
Then I do the following tests: See attachement

1.- I test the monitor disconnecting the wires to A conectors, the same, 1 second image.
2.- Reconect A wires and disconect B wires, and I don't have the one second image.
3.- Conect the A wires in B connectors, and have 1 second image
4.- Conect the B wires in A connectors, and I don't have the one second image.
The conclusions are: that both lamps are O.K., the problem is in the A part of the board, and B part is O.K.
Then I decided to change the fault from A part to B part, changing the A parts components by the B parts components
Then I number the inverter output transformers and the high voltage capacitors "27J 3KV" (1, 2, 3, and 4 ) and disassemble all of them.
Mount the transformers and the capacitors in inverse order (4, 3, 2, and 1), trying to change the fault to the other side of the board.
Test the monitor with these changes, and what is my surprise that the monitor works o.k.
Conclusions:
One of the solderings has a cold joint, that don't repaired when I resolder ¡¡¡¡¡¡¡¡¡¡¡¡¡ INCREDIBLE !!!!!!!!!!!!!!!
The cold joint can blow up the transistors
I hope that this append can help others that has the same problem.

[arneson]

Re: Dell E172fpb

I found that very interesting about the resoldering not working.
Maybe I could be corrected but I believe there are some solder connections that could possibly be overlooked.
I'm talking about the leg connections in the transformer frame.
Each leg would have to become very hot to reflow the second tiny wire connection higher up.
Unless of course they are welded inside, I haven't torn one apart yet to see.
I've mentioned before that I really suspect those high voltage caps of arking,
but this gives me a new direction.

[RunnerPack]

Re: Dell E172fpb

Hello, all

I just got one of these rassafrackin' monitors from a flea-market. I only paid $7.50, so I sorta expected it not to work. I have the "blinks on then the power light (and CCFLs, dimly) blink continuously until power button held for a second" problem, not the "blinks on then power light steady but no backlight" problem.

I've already taken it apart thanks to the instructions on this thread, but I have some questions before I proceed:

1. Is it possible that reflowing the joints in the affected area could fix it w/out needing new transistors/caps?

2. If it doesn't and I want to, e.g. use this panel to build a Lumenlab projector, how would I disable the backlight drivers altogether while making the logic think they're functioning normally (i.e. how do I stop the power light flashing)?

If I do that, I'll try to carefully remove the (tested good) caps, big transformers, the little round inductors, the TI1451 and any other semiconductors in the area and offer them to other E172FP owners at a reasonable price.

3. Has anyone tried replacing the driver circuitry altogether with one or more of those ones you get with PC case-modder "neon" kits?

Thanks to all who've added info to this great thread!

[Krankshaft]

Re: Dell E172fpb

No sadly if no solder joints are cracked resoldering won't do any good.

It is a good idea however to resolder the pins on the inverter transformers and any questionable joints around the inverter area.

There really is no reason to hack up the board. I have seen those guides but with all of that effort to replace the inverter side of the supply which is basically what you are doing.

You could have repaired the inverter on the PSU board itself.

Check the C5707 transistors one of them is probably shorted.

Replace them in pairs.

If none of the caps are bulged then you should be good to go.

[RunnerPack]

Re: Dell E172fpb

Well, I didn't say anything about "hacking up the board".

In #2 I was just wondering which component to remove/trace to cut to disconnect the inverter circuit(s) from the PSU (along with removing R750) since a backlight is redundant in a projector.

Likewise, in #3, I just meant to circumvent the inverters on the board and add those little 12VDC ones off to the side somewhere and hook them to a supply rail and the CCFLs.

I can't really tell whether any joints are cracked, but I thought someone said it was dirty leads that made the bad connections. I was just curious if it's possible that the behavior could be explained by just a bad joint, without the transistors/caps having been damaged.

Oh, well. I'm about to clean the joints now, so I guess we'll see.