dell E173Fpf burnt parts

[Djihatch]

Hi,

Thanks by advance for those who will help me ;-)

I've got a non working Dell E173Fpf and I would try to fix it.
Q850 is shorted and I have to replace it. My problem is that I can't read R856, C856 and R861 values anymore (see pictures)...
I already searched on previous posts, but values that are given by forum members are not the same from a topic to another, and noone seems to be aware of C856 value...
I searched for E173Fpf service manual, but no way.... Only E173Fp service manual is available.

Anyone can help ? ;-)

Thank you

[Rtech]

Re: dell E173Fpf burnt parts

R856 is 15ohms,R861 is 47ohms,C856 measures 29.4uF on my meter, so 33uF looks good.However these boards can fail in a big way, so suggest you also check R859,R852,D851 and D853.Also you will need to change C857,as that has no doubt been stressed due to the failure,and the PWM chip itself may have caused the failure,and be blown so would replace the SG6841 also.Good luck.

[Djihatch]

Re: dell E173Fpf burnt parts

Thanks a lot.

I'll follow your advices and let you know.

Have a nice day.

[mpgasque]

Re: dell E173Fpf burnt parts

Hi. I have the same problem, no display, but my power light is a steady green. I swapped in a good power/logic/inverter board and the display came up just fine. Your picture is exactly my system board. On the bad system board nothing seems to be blown out or burnt. The person I got the display from said the picture just quit. I tested the typical 220uf 25vcaps and their good. Sooo, I think the low voltage power supply is ok, good power light and the flashlight test reveals an image on the screen, but no back-light. Since both back-lights quit together, I'm thinking inverter power supply. I put in another power mosfet (Q850) but no dice. My question, did you guys that started this thread ever reach an answer in your case? Thanks.

[retiredcaps]

Re: dell E173Fpf burnt parts

Your picture is exactly my system board.

1) We normally ask for people to post clear focused pictures of their OWN boards because there might be slight, but important, nuances and manufacturers are known to use differerent revisions of the boards while keeping the same lcd model number.

2) If you have no backlight, check the 8 pin mosfets for shorts that are next to the 2 caps on the inverter board. The OP's pictures are too fuzzy and unclear to give a PCB designation which is another reason why you should post your own pictures.

[Rtech]

Re: dell E173Fpf burnt parts

If you have changed C6 and C26,then check the Schottky Diode D854,then check the resistance of the secondaries of the Inverter Transformers T1 and T2,between pins 8 and 11 of each, you should get approx 530 ohms,with no significant difference.

[mpgasque]

Re: dell E173Fpf burnt parts

Thanks so much for the replies. Good point about specific pictures of my board, all kind of small changes could have occurred. When I get a chance I will post them as you suggest.
The resistance of the transformers are just what you said, 529 and 530 ohms for T1 and T2 respectively. I tested C6 And C26 with a cap meter after pulling them out of the board and got around 210uf each so I think their good and I put them back in.
I tested the Schottky Diode (D854) and got .194 (ohms I believe) from each outer leg to the inner cathode, and when reversed an open circuit . I have some new D854's that I could drop in but it doesn't seem to be bad. The numbers off the 8 pin mosfets are 9960m and below that 517352. I'll look them up to get their datasheet.
Thanks again, I hate to throw away a good board that has one little bad part on it. Finding that component is, well... not so easy sometimes.

[Rtech]

Re: dell E173Fpf burnt parts

To get 0.194 when measuring the Schottky,you were using the Diode test feature on your meter ?? , so what ypu were reading was the voltage drop across the diode junctions,and thats fine,,,if that had been an ohms reading then the diode was short circuit.

[mpgasque]

Re: dell E173Fpf burnt parts

Yes, your right. I used the diode function on my multi meter. The voltage drop across the junction was my second thought of what the reading actually was. When the probes were reversed I had an open circuit. Thanks for the insight. I'll continue to examine/test and post my results as they become available. Thanks for all the replies.

[ben7]

Re: dell E173Fpf burnt parts

R856 is 15ohms,R861 is 47ohms,C856 measures 29.4uF on my meter, so 33uF looks good.However these boards can fail in a big way, so suggest you also check R859,R852,D851 and D853.Also you will need to change C857,as that has no doubt been stressed due to the failure,and the PWM chip itself may have caused the failure,and be blown so would replace the SG6841 also.Good luck.

umm I think that C856 is not 29uF, its soo small to be that large of a capacitance! BTW you can't measure the capacitance of a capacitor in circuit! thats why you got such a high reading :/

it looks like a large surge caused an arc, zapping those parts. I would guess the SG6841 controller chip is zapped too.

-Ben

[Rtech]

Re: dell E173Fpf burnt parts

umm I think that C856 is not 29uF, its soo small to be that large of a capacitance! BTW you can't measure the capacitance of a capacitor in circuit! thats why you got such a high reading :/

it looks like a large surge caused an arc, zapping those parts. I would guess the SG6841 controller chip is zapped too.

-Ben

The Poster has already been advised to change the SG6841.This is normal for this Board with this fault.BTW thanks for the Electronics lesson...after 40 years I would not have known that.

[Djihatch]

Re: dell E173Fpf burnt parts

Hi,

Thanks to all of us who gave me advices about my problem.

I gave up with this monitor... My local dealer couldn't get some parts, and shipping was too expensive from other dealers.

But I didn't waste your time : from this first experience, and by reading this forum, I fixed more than 20 LCD monitors for my school, and 2 32 inches tv (for me ;-) ).

So thanks again to all of us. I hope that one day I'll get enough experienced to help other people.

Hope to see you soon !

Djihatch

[PlainBill]

Re: dell E173Fpf burnt parts

Hi,

Thanks to all of us who gave me advices about my problem.

I gave up with this monitor... My local dealer couldn't get some parts, and shipping was too expensive from other dealers.

But I didn't waste your time : from this first experience, and by reading this forum, I fixed more than 20 LCD monitors for my school, and 2 32 inches tv (for me ;-) ).

So thanks again to all of us. I hope that one day I'll get enough experienced to help other people.

Hope to see you soon !

Djihatch

What!!! You repaired 20 monitors and 2 TVs and only posted twice with problems? The normal ratio is closer to 20 questions per monitor (some people ask that many before they can get it apart ).

Give yourself a Well Done!

PlainBill

[Djihatch]

Re: dell E173Fpf burnt parts

Thank you !

In fact I like to read every post even when this is not about a monitor/TV that I own. That's why I don't need to post everytime ( Don't worry, a 37 and 40 inches flat TV with video problems wait for me, and I will probably need your help !).

Just a little feedback for noobs like me :

For the 1st TV (Samsung 32') : That was a specialised IC (F9222L) that was faulty.

For the 2nd TV (LG 32') : Obvious bad caps. 10 minutes to fix this one !

For the 20 monitors :

-12 with obvious bad caps.
-2 with bad caps (but good shape, so had to be tested with a DMM)
-3 with bad solder (most of the time on big components like transformers or coils)
-2 with bad CCFL solder in LCD panel (Had to unmount them, not easy, but with time...).
-1 with a bad connection between two boards.

The ones that were hardest to fix ? The ones with a bad CCFL ( that was before I took some spare CCFL from a broken panel to check a faulty monitor).

I hope it will be usefull.

Thanks again for this website

[PlainBill]

Re: dell E173Fpf burnt parts

Thank you !

In fact I like to read every post even when this is not about a monitor/TV that I own. That's why I don't need to post everytime ( Don't worry, a 37 and 40 inches flat TV with video problems wait for me, and I will probably need your help !).

Just a little feedback for noobs like me :

For the 1st TV (Samsung 32') : That was a specialised IC (F9222L) that was faulty.

For the 2nd TV (LG 32') : Obvious bad caps. 10 minutes to fix this one !

For the 20 monitors :

-12 with obvious bad caps.
-2 with bad caps (but good shape, so had to be tested with a DMM)
-3 with bad solder (most of the time on big components like transformers or coils)
-2 with bad CCFL solder in LCD panel (Had to unmount them, not easy, but with time...).
-1 with a bad connection between two boards.

The ones that were hardest to fix ? The ones with a bad CCFL ( that was before I took some spare CCFL from a broken panel to check a faulty monitor).

I hope it will be usefull.

Thanks again for this website

You are overly pessimistic. There are more differences between a 5 year old 19" Polaroid TV and a 2 year old 27" Vizio than between the two year old Vizio and a 47" Samsung of the same age. Plasma is more complex that LCD, but in all cases it's a matter of recognizing symptoms.

PlainBill

[picturevalve]

Re: dell E173Fpf burnt parts

I was given a faulty one of these a few years back but could not get any data that matched my board. Today I find this thread. My board has the mains fuse well blackened, R852 and C868 destroyed (totally) with a nice big scorch mark on the heatsink. The board is pristine and all caps read o/k. Does anyone have the values of the 2 components above?The resistor is in the +ve line from C854, some sort of surge limiter? and the cap is across the ht to ground after it.
With any luck it was just a cap. failure. In the op image they're the resistor and larger ceramic between the 100uF 450v cap and the heatsink of Q850.

[picturevalve]

Re: dell E173Fpf burnt parts

Looking at op jpeg, R852 looks like it could be 0.21 ohm?

[TechGeek]

Re: dell E173Fpf burnt parts

R861 appears to be a 470-ohm or 470k-ohm resistor. I think, though.

[picturevalve]

Re: dell E173Fpf burnt parts

R861 appears to be a 470-ohm or 470k-ohm resistor. I think, though.

No, R861 is 47 ohm.

[budm]

Re: dell E173Fpf burnt parts

IC spec.
BTW, you should also replace that IC U850, when that power MOSFET shorted out it dumped high Voltage into the Gate drive output of the IC so that Rg (R856) is damaged).
R861 is Rsense, R859 is the Source resistor (does it also show open circuit?).
R853, 854 are RIN for the internal charge pump to get the IC started.