Dell E177FPb - White Screen

[momaka]

Re: Dell E177FPb - White Screen

Congrats!
Now when you find a "white screen", you know what to check . Can (and usually is) an easy fix if there's just a shorted ceramic cap. I like it even better than bad caps fixes because I have so many junk boards I can pull ceramic caps off of that I'll probably never run out.

[budm]

Re: Dell E177FPb - White Screen

Great job!

[vela]

Re: Dell E177FPb - White Screen

Folks, I am delighted to report that with the scounged up ceramic caps and a new SMD fuse (3A) on the T-CON board, the monitor is back up and running. Thanks for all your help! I think I am hooked and am actively looking for "broken" monitors to fix :-) .

[vela]

Re: Dell E177FPb - White Screen

Totally understand about the fuses. I am awaiting the parts and will report back when installed. The catch with this particular T-con is that the populated side of the board flips down against the back of the lcd panel. So there is not much space to insert any larger scale components and still fold down the board and reassemble. The fuse in particular is just below the connector to the other board and really leaves no wiggle room.

Parts should be here in a couple of days...

[budm]

Re: Dell E177FPb - White Screen

You do not even have to remove the old blown fuse, you just lay the new one right on top and solder both ends to the old fuse.
YOU CAN GET 22UF 25V Ceramic SMD from MOUSER, for example:
http://www.mouser.com/Passive-Compon...ERAMIC&FS=True

[retiredcaps]

Re: Dell E177FPb - White Screen

That was probably me.

Correct.

Fuses are there for a reason.

Otherwise, the cost cutters would have removed it.

[momaka]

Re: Dell E177FPb - White Screen

Cool idea using an electrolytic cap. Should have checked in here first before scrounging around and pulling a similarly sized ceramic cap off an old ethernet card and plugging it in because I saw that approach suggested in some other thread here when I was browsing some time back.

That was probably me. I've been using that method for a while now, both for LCD monitor T-con boards and other electronics too. Never had a problem with it. Oldest t-con repairs I have are (2 monitors: 19" Samsung SyncM. 931B and 19" HP W19b) about 2.5 years old now and as far as I know, both monitors still work fine.

SMD ceramic caps are usually rated for 32V and above, so most likely you won't have a problem.

Trying to decide if I should order replacements or go the TOM66 route and short it

Ok, but if you do and something else smokes, I ain't going to help .

Fuses are there for a reason. If you really don't want to get the exact SMD fuse replacement, then at least jurry-rig a standard fuse with some wires and hook that up to the t-con.

If there's no fuse on the t-con or it's over rated and there is a fault on the t-con, more than likely something else will blow too. I've seen that happen on a 17" Dell (the fuse was too beefy apparently) - I ended up spending another 2 hours looking for the problem. Finally found a completely burned transistor on the video/logic board. Had to do some jurry-rigging on that monitor to get it working.
Save yourself the trouble and put a fuse of some sort in there.

[vela]

Re: Dell E177FPb - White Screen

Cool idea using an electrolytic cap. Should have checked in here first before scrounging around and pulling a similarly sized ceramic cap off an old ethernet card and plugging it in because I saw that approach suggested in some other thread here when I was browsing some time back. I guess there is no telling if the substitute is rated for 25V or not. Unfortunately, I don't have a way to measure capacitance, so getting another similar one off the board is not going to help.
Still stuck on the fuse, though. Trying to decide if I should order replacements or go the TOM66 route and short it

[retiredcaps]

Re: Dell E177FPb - White Screen

22uF 25V sounds about right, juts make sure to install it with correct polarity by checking the voltage on other caps that are in parallel with this bad cap, the MLCC does not have polarity.

This is the cap I used.

https://www.badcaps.net/store/produc...roducts_id=102

Yes, I checked with a multimeter to see which side was ground.

BTW, my guess as to uF was based on measuring other ceramic caps on the logic board of the same size with my multimeter set on capacitance measurement mode.

[budm]

Re: Dell E177FPb - White Screen

22uF 25V sounds about right, juts make sure to install it with correct polarity by checking the voltage on other caps that are in parallel with this bad cap, the MLCC does not have polarity.

[retiredcaps]

Re: Dell E177FPb - White Screen

Found the shorted ceramic cap (C24) some time back, but I don't have any replacements. Trying to get some so I can replace cap and the fuse on the board and try it.

I didn't even bother to try with a ceramic. See here

https://www.badcaps.net/forum/showpo...1&postcount=23

I didn't take pictures on purpose due to my terrible solder job. 3 months of daily use and it still works.

[budm]

Re: Dell E177FPb - White Screen

Was it the last one you removed? Can you read the value of the good one ?

[vela]

Re: Dell E177FPb - White Screen

Quick update: Found the shorted ceramic cap (C24) some time back, but I don't have any replacements. Trying to get some so I can replace cap and the fuse on the board and try it. The wait is killing me :-(

[vela]

Re: Dell E177FPb - White Screen

Thanks for the advice. It is really 1 ohm on the DMM set to measure resistance. Strange thing is that it starts off shorted and builds up to 1 ohm, which might suggest that a "shorted" cap is getting charged but pretty poorly. I was checking all the caps and as you said, a whole lot of them are showing as shorted, no doubt because they are all in parallel.

I'll go through these steps and report back what I find. Thanks again!

[budm]

Re: Dell E177FPb - White Screen

And be real careful if you are going to put the old caps back in place (check for short after install each cap back in place before installing the next one), they can easily be damaged during removal and re-installation. You may want to look for fine cracks on the body of the cap also.

[momaka]

Re: Dell E177FPb - White Screen

I did measure the resistance from AVDD1 to ground on my t_con and it is just 1 ohm... Does this shed light on where the problem might be?

Is it a "1" on the left side of the screen or 1.0 Ohms?

The latter means that there's a short on AVDD1. If that's the case, then more than likely one of the ceramic caps connected between AVDD1 and ground is shorted. Finding out which is the hard part since there more than one and they are all connected in parallel (so if one is shorted, they all shorted).

If you have decent SMD soldering skills, then start removing the ceramic caps connected to AVDD1, one by one. (I would say, start with the ones next to L1 as those are the most likely suspects.) Make sure to check each ceramic cap once you remove it from the board - if the cap doesn't show open circuit (infinite resistance) out of the board, it's bad. Also make sure to check resistance between AVDD1 and ground after removing each cap. You should get about 100 Ohms or more once the short is gone.

[vela]

Re: Dell E177FPb - White Screen

I am a newbie at fixing monitors, but have been reading a number of threads with great interest. Very impressed with the knowledge and expertise of the poster and even more so with everyone's willingness to share. This particular thread was especially interesting as my Dell w2207 monitor is also showing the White Screen issue and I was hoping to follow this thread and momaka's expert diagnosis to conclusion, but unfortunately tom66 took a shortcut

I did measure the resistance from AVDD1 to ground on my t_con and it is just 1 ohm. The resistances for VGH1 (71.2Kohms) and VEE1 (6.08Kohms) are much higher. Does this shed light on where the problem might be? Any help will be greatly appreciated.

I am also testing the ceramic caps on the t_con for shorts, just by measuring the resistance using a DMM. Hope that is the right way to do it.

[tom66]

Re: Dell E177FPb - White Screen

That shorted ceramic cap was mostly likely on the main step-up rail, AVDD1. Would have taken 5 seconds to check it with a multimeter and avoid all of that damage above... Oh well, too late now .
I hope you get fixed, though. Looks like you're almost there. And at least the monitor works somewhat now.

It was between the ribbons, probably AVDD1. Did check for shorts from 5V to ground but now I think about it: for a boost converter there's a series diode, and my 0.3V test voltage from the multimeter wouldn't bias the diode so the short wouldn't be found.

[momaka]

Re: Dell E177FPb - White Screen

That shorted ceramic cap was mostly likely on the main step-up rail, AVDD1. Would have taken 5 seconds to check it with a multimeter and avoid all of that damage above... Oh well, too late now .
I hope you get fixed, though. Looks like you're almost there. And at least the monitor works somewhat now.

[tom66]

Re: Dell E177FPb - White Screen

Well, this monitor got put on the back burner, but I decided to have one last shot at it again.

I did the unthinkable, of course - I bridged the fuse with some solder. Heh, I thought the monitor may as well be scrap, anyway. So, plugged it in, and it seems like it didn't want to come on, but then the screen started flickering and it powered up but no power LED because 5V was shorted. I heard the occasional SMPS click from a shorted output.

Then smoke comes from one of the MLCCs. I guess that was the shorted one then... I must have missed it in my tests or maybe it was only short circuit with a higher voltage.

Removed it... Got a display (no signal!)

BUT... it's very blurred and pretty poor. And after a while, it goes away and goes white again. And the PCB got a bit... melted... from that MLCC. So I'll have to figure a way out of putting a cap on there.