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-   -   Issue with Westinghouse 19" LCD Monitor (large pics) (https://www.badcaps.net/forum/showthread.php?t=6723)

mobaar 03-02-2009 04:51 PM

Issue with Westinghouse 19" LCD Monitor (large pics)
 
Hi all,

I actually came upon this website quite by accident. As it turned out, I came here by doing a Google search for a particular part (to be explained below) and lo and behold, I think I may have found the place that might save me a headache, two arms, and perhaps a portion of my leg.

So here's the issue:

I have a Westinghouse L1975NW 19" LCD monitor...well, it's actually a nonworking one. One day I came into my office to find the screen blank, which typically does not bother me since I use suspend, but when I tried to startup the computer, the screen stayed black, and the LED at the front turned from Amber to Green (indicating that it was receiving a signal). Having no idea what to do in this case, I called Westinghouse, who told me it sounded like the backlight was out and referred me to Best Buy (where it was bought for me) who told me it was a 1-year warranty and I was on month 18. So no dice on the warranty.

Being the tinkerer that I am (and I'm not too shabby with computers, I just have never gone to the circuitry level of hardware), I decided to open it up and see if maybe there was a loose wire or some obvious issue that I might be able to fix.

Well, this is where the fun begins...I'm hoping all of you can help me out. I don't see any obvious problems, but a couple of things stuck out to me and maybe you can help me diagnose and maybe even repair the problem. It's a $180 monitor, so it's not the end of the world if I replace it, but I've got a baby on the way and would prefer to do this in the cheap.

Alright, here's the pictures:

http://i3.photobucket.com/albums/y60/mobaar/X1.jpg
Here's the layout. From what I can ascertain, the board on the right is much of the input processing, controlling the rest of the board, etc. and the board on the left largely consists of the internal power supply, power processing, and what looks to be 4 outputs to the backlight (is that correct? maybe it's the video, but I thought that would be what goes up from the right board). Am I reading this correctly?

http://i3.photobucket.com/albums/y60/mobaar/X2.jpg
Here's what I thought might be the culprit. There is a dark spot around that top MOSFET, the metal on it is discolored, and it is really the only thing that jumps out to me. However, since you guys are smarter at this than I am, I'll include some detail pics of the rest of the board:

http://i3.photobucket.com/albums/y60/mobaar/X3.jpg
http://i3.photobucket.com/albums/y60/mobaar/X4.jpg
http://i3.photobucket.com/albums/y60/mobaar/X6.jpg
http://i3.photobucket.com/albums/y60/mobaar/X7.jpg
http://i3.photobucket.com/albums/y60/mobaar/X8.jpg

The underside of the board to me didn't seem to have anything that really stuck out to me, but I tried to capture some of the discoloration under that same MOSFET:

http://i3.photobucket.com/albums/y60/mobaar/X9.jpg

And here's the MOSFET as blown-up as I can get without pixellating:

http://i3.photobucket.com/albums/y60/mobaar/X5.jpg


So I have a couple of questions.

1.) I know that you cannot tell me and be 100% sure that the MOSFET needs to be replaced, but does it look like it's the likely culprit? I also know that it might not be the only issue; if the MOSFET failed, perhaps something else went screwy too.
2.) How do I test this board other than plugging it in and pressing the power button? I have a multimeter, although I doubt that will help me too much. Maybe I'm wrong on that one too :). But I'd really appreciate any help you can offer!

Thanks guys! I know I'm in good hands! :)

Collin


PS: I found this place looking for that specific model of MOSFET. It's the same one discussed here: http://www.badcaps.net/forum/showthread.php?t=6636

EGuevarae 03-02-2009 05:02 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Quote:

Originally Posted by mobaar
Hi all,

I actually came upon this website quite by accident. As it turned out, I came here by doing a Google search for a particular part (to be explained below) and lo and behold, I think I may have found the place that might save me a headache, two arms, and perhaps a portion of my leg.

So here's the issue:

I have a Westinghouse L1975NW 19" LCD monitor...well, it's actually a nonworking one. One day I came into my office to find the screen blank, which typically does not bother me since I use suspend, but when I tried to startup the computer, the screen stayed black, and the LED at the front turned from Amber to Green (indicating that it was receiving a signal). Having no idea what to do in this case, I called Westinghouse, who told me it sounded like the backlight was out and referred me to Best Buy (where it was bought for me) who told me it was a 1-year warranty and I was on month 18. So no dice on the warranty.

Being the tinkerer that I am (and I'm not too shabby with computers, I just have never gone to the circuitry level of hardware), I decided to open it up and see if maybe there was a loose wire or some obvious issue that I might be able to fix.

Well, this is where the fun begins...I'm hoping all of you can help me out. I don't see any obvious problems, but a couple of things stuck out to me and maybe you can help me diagnose and maybe even repair the problem. It's a $180 monitor, so it's not the end of the world if I replace it, but I've got a baby on the way and would prefer to do this in the cheap.

Alright, here's the pictures:

http://i3.photobucket.com/albums/y60/mobaar/X1.jpg
Here's the layout. From what I can ascertain, the board on the right is much of the input processing, controlling the rest of the board, etc. and the board on the left largely consists of the internal power supply, power processing, and what looks to be 4 outputs to the backlight (is that correct? maybe it's the video, but I thought that would be what goes up from the right board). Am I reading this correctly?

http://i3.photobucket.com/albums/y60/mobaar/X2.jpg
Here's what I thought might be the culprit. There is a dark spot around that top MOSFET, the metal on it is discolored, and it is really the only thing that jumps out to me. However, since you guys are smarter at this than I am, I'll include some detail pics of the rest of the board:

http://i3.photobucket.com/albums/y60/mobaar/X3.jpg
http://i3.photobucket.com/albums/y60/mobaar/X4.jpg
http://i3.photobucket.com/albums/y60/mobaar/X6.jpg
http://i3.photobucket.com/albums/y60/mobaar/X7.jpg
http://i3.photobucket.com/albums/y60/mobaar/X8.jpg

The underside of the board to me didn't seem to have anything that really stuck out to me, but I tried to capture some of the discoloration under that same MOSFET:

http://i3.photobucket.com/albums/y60/mobaar/X9.jpg

And here's the MOSFET as blown-up as I can get without pixellating:

http://i3.photobucket.com/albums/y60/mobaar/X5.jpg


So I have a couple of questions.

1.) I know that you cannot tell me and be 100% sure that the MOSFET needs to be replaced, but does it look like it's the likely culprit? I also know that it might not be the only issue; if the MOSFET failed, perhaps something else went screwy too.
2.) How do I test this board other than plugging it in and pressing the power button? I have a multimeter, although I doubt that will help me too much. Maybe I'm wrong on that one too :). But I'd really appreciate any help you can offer!

Thanks guys! I know I'm in good hands! :)

Collin


PS: I found this place looking for that specific model of MOSFET. It's the same one discussed here: http://www.badcaps.net/forum/showthread.php?t=6636

Welcome to the forums.
I was about to refer you to the thread I started, but you got it already. I have the same problem, and the sape suspicious MOSFET, but I have not replaced it. It is a less than a dollar part, plus like 7~8 shipping, and for a monitor that size, it is worth it. I'm just messing with others now and didn't get back to it again. I must have the good MOSFET somewhere around here. I can send it to you (if you can change it, that is) to see if it is the only problem you have, and if it is, you just buy the two (replace them in pairs, per PCBONEZ suggestion)a dn send me the one I sent you and the one you have, so I can test my unit. Sounds fair?
But first you must be sure there's no other problem in the PSU. Check the brand/capacitance/V Rating and series of the installed caps and post the info. They look like CapXon or Elite, and they must be changed as a precaution measure even if they look good.

And the board that has the MOSFET is the PSU & Inverter board (yours, like mine, has the inverter side bad).
Again, welcome to Badcaps.net :cheers:

mobaar 03-02-2009 06:01 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Well I found these 2 MOSFETs on eBay for $8 shipped, with the 40T03 specification:

http://cgi.ebay.com/LOT-OF-(2)-TWO-4...228189007r3997

Would those work? Maybe with that I'd only need to replace 1?

How about the other problem....is there an easy way to see if there are any additional issues?

Thanks!

Collin

mobaar 03-02-2009 06:19 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
For the capacitors, here's what I see:

CapXon:
3x 25V 220μF
2x 25V 1000μF
1x 10V 2200μF
1x 10V 1000μF
1x 50V 47μF
1x 50V 22μF

They're all CapXon but the big guy is turned so I cannot see it and the heatsink material is holding it down.

Collin

EGuevarae 03-02-2009 06:21 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Quote:

Originally Posted by mobaar
Well I found these 2 MOSFETs on eBay for $8 shipped, with the 40T03 specification:

http://cgi.ebay.com/LOT-OF-(2)-TWO-4...228189007r3997

Would those work? Maybe with that I'd only need to replace 1?

How about the other problem....is there an easy way to see if there are any additional issues?

Thanks!

Collin

Even if only one failed, replace them both. And for the other issues, again, you need to post info on the caps on your PSU, and voltage readings if possible.

japlytic 03-02-2009 07:02 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
I see a few bulging capacitors on the power board.
Try replacing them first. If it works, replace the rest on the power board.

The original CapXon units are general purpose - not designed for high frequency use.

EGuevarae 03-02-2009 07:13 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Quote:

Originally Posted by eguevarae
Even if only one failed, replace them both. And for the other issues, again, you need to post info on the caps on your PSU, and voltage readings if possible.

I guess my post crossed with yours, and you had already posted teh cap data. As japlityc said, replace them, as they are prone to fail, and you can not test for sure with those on. Even if they are good now, you'll have to open the LCD another day just to replace those. You are already there, so why you don't do it now?

mobaar 03-02-2009 09:17 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Thanks all for your help! I will post to you guys with results...now to find some capacitors... :)

PCBONEZ 03-02-2009 09:35 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Capxon ~what~ ?
Not all Capxon are created equal.

mobaar 03-02-2009 09:50 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Well, at this point it's looking like I'll probably just order some Nichicon capacitors from Mouser. Maybe it's best to share what I'm thinking of getting and getting your feedback? I just don't want to be "that person" that is asking obvious questions that are answered in the FAQ, which I'm still reading through to make sure I'm not being redundant :).

Collin

mobaar 03-02-2009 10:21 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Ok, here is what I've put together at Mouser:

Mouser #: 647-UPTW6101MHD
Mfr. #: UPTW6101MHD
Desc.: Low Impedance Aluminum Electrolytic Capacitors - 105 Degree 100uF 420V 18X35.5 20%

Mouser #: 647-UVZ1H220MDD
Mfr. #: UVZ1H220MDD
Desc.: Radial Aluminum Electrolytic Capacitors - 105 Degree 22uF 50V 105c 5x11 20% 2LS

Mouser #: 647-UVZ1H470MED
Mfr. #: UVZ1H470MED
Desc.: Radial Aluminum Electrolytic Capacitors - 105 Degree 47uF 50V 105c 6.3x11 20% 2.5LS

Mouser #: 647-UKT1A102MPD
Mfr. #: UKT1A102MPD
Desc.: Audio Electrolytic Capacitors 1000uF 10V 20%

Mouser #: 647-UKT1A222MHD
Mfr. #: UKT1A222MHD
Desc.: Audio Electrolytic Capacitors 2200uF 10V 20%

Mouser #: 647-UHE1E102MHD3
Mfr. #: UHE1E102MHD3
Desc.: Low Impedance Aluminum Electrolytic Capacitors - 105 Degree 1000uF 25V 105c 16x15 20% 7.5LS

Mouser #: 647-UHE1E221MPD
Mfr. #: UHE1E221MPD
Desc.: Low Impedance Aluminum Electrolytic Capacitors - 105 Degree 220uF 25V 105c 8x11.5 20% 3.5LS

--------------------------------------

Am I at the very least on the right track? I went with 420V on the big boy capacitor (it is 400V/100μF) because the 400V ones were all on backorder...

Any help would be greatly appreciated. I'm looking forward to my new life as a cap'er but I want to know that I'm at least on the right track :)

Collin

EGuevarae 03-02-2009 10:29 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Quote:

Originally Posted by mobaar
Ok, here is what I've put together at Mouser:

Mouser #: 647-UPTW6101MHD
Mfr. #: UPTW6101MHD
Desc.: Low Impedance Aluminum Electrolytic Capacitors - 105 Degree 100uF 420V 18X35.5 20%

Mouser #: 647-UVZ1H220MDD
Mfr. #: UVZ1H220MDD
Desc.: Radial Aluminum Electrolytic Capacitors - 105 Degree 22uF 50V 105c 5x11 20% 2LS

Mouser #: 647-UVZ1H470MED
Mfr. #: UVZ1H470MED
Desc.: Radial Aluminum Electrolytic Capacitors - 105 Degree 47uF 50V 105c 6.3x11 20% 2.5LS

Mouser #: 647-UKT1A102MPD
Mfr. #: UKT1A102MPD
Desc.: Audio Electrolytic Capacitors 1000uF 10V 20%

Mouser #: 647-UKT1A222MHD
Mfr. #: UKT1A222MHD
Desc.: Audio Electrolytic Capacitors 2200uF 10V 20%

Mouser #: 647-UHE1E102MHD3
Mfr. #: UHE1E102MHD3
Desc.: Low Impedance Aluminum Electrolytic Capacitors - 105 Degree 1000uF 25V 105c 16x15 20% 7.5LS

Mouser #: 647-UHE1E221MPD
Mfr. #: UHE1E221MPD
Desc.: Low Impedance Aluminum Electrolytic Capacitors - 105 Degree 220uF 25V 105c 8x11.5 20% 3.5LS

--------------------------------------

Am I at the very least on the right track? I went with 420V on the big boy capacitor (it is 400V/100μF) because the 400V ones were all on backorder...

Any help would be greatly appreciated. I'm looking forward to my new life as a cap'er but I want to know that I'm at least on the right track :)

Collin

It looks okay to me, but wait for confirmation from PCBONEZ.... he's the man.
You are sticking with 105c and that's good. Panasonic FCs have been suggested more than once here, and I personally have used them without problems, but confirmation from a Senior would be better.
And for the big cap, they rarely fail (I haven't seen one so far and I've read around here that they do not fail that often), but again, wait for confirmation from him.
Eduardo

mobaar 03-02-2009 10:45 PM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Thanks, Eduardo. I'm calling it a night for tonight so we'll see what develops tomorrow morning. I'll keep the shopping cart open so I can pick up where I left off tonight.

Thanks again!

Collin

gdement 03-03-2009 01:55 AM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Quote:

Originally Posted by mobaar
Mouser #: 647-UKT1A102MPD
Mfr. #: UKT1A102MPD
Desc.: Audio Electrolytic Capacitors 1000uF 10V 20%

Mouser #: 647-UKT1A222MHD
Mfr. #: UKT1A222MHD
Desc.: Audio Electrolytic Capacitors 2200uF 10V 20%

I'm concerned about these. These sizes might need to be low-ESR caps, and Nichicon KT series don't appear to be low ESR.
Do they have these in the Nichicon HE? That would be a better choice.

It's best if you can read the series code off the old caps, as that would indicate what sort of spec the originals are. The series is usually 2 letters. But without that information the Nichicon HE are a good bet, or United/Nippon Chemicon KY (different brand, equivalent specs).


Quote:

Mouser #: 647-UHE1E102MHD3
Mfr. #: UHE1E102MHD3
Desc.: Low Impedance Aluminum Electrolytic Capacitors - 105 Degree 1000uF 25V 105c 16x15 20% 7.5LS
The physical size on this one is 16x15mm... are you sure that's what the old one is? It's hard to tell from a photo but it doesn't look that fat.

But if you do go narrower then you also have to pay attention to height, make sure it will still fit vertically.
UHE1E102MHD6 is 12.5x20mm (last digit is a 6 vs 3 above).

PCBONEZ 03-03-2009 02:27 AM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Some series of Capxon have significantly low ESR.
Up around FM and possibly even MBZ.
If that's the case for for any of the original caps them none listed are adequate for those specific originals.

That's why I said:
>>
Capxon ~what~ ?
Not all Capxon are created equal.
<<

If you don't tell me what series of Capxon the originals are then I can't verify replacements.

What I 'usually' see in LCD PSU OP filter sections sections need at least FC.
VZ and KT aren't gonna cut it.

mobaar 03-03-2009 06:01 AM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Updating with the 2-letter code:

3x 25V 220μF (KF)
2x 25V 1000μF (KF)
1x 10V 2200μF (KF)
1x 10V 1000μF (KF)
1x 50V 47μF (GL)
1x 50V 22μF (GL)

1x 400V 100μF (KM)

This is all still pretty new to me. I know low ESR is where I want to go, and I even see the parts list for Nichicon high-to-low ESR, I just didn't find my particular caps listed...maybe that's because they were too high of ESR. I'll do some more searching :)

Collin

Krankshaft 03-03-2009 08:16 AM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Be sure to measure the old caps in mms and compare the sizes to the data sheet of the caps you are buying.

These monitors are very cramped and you don't want to be unable to install the cover when you're done.

This is especially important for the line cap if you intend to replace it. Also if the original line cap is a radial and the one you are buying is a radial snap in just clip the old caps leads off right at the body then bend the new snap in caps legs down and the solder the old caps leads to the new cap.

To go even further I usually put a puddle of hot glue beneath the cap on the PCB and press it down onto the board until the glue cools to secure it firmly.

To test the FET just use the standard transistor test procedure. Set the DMM to the diode check function test from source to gate and reverse the probes a voltage drop should only be observed in one direction.

Do the same from drain to gate the same testing rule applies voltage drop in only one direction.

The heating of that component is evident on the board and since it's neighbor didn't brown the PCB too it wasn't a result of normal operation. I'd be willing to bet you will find it's shorted.

You can get cheap DMMs at Ratshack the pocket model (my first DMM) runs about 20 bucks.

Krankshaft 03-03-2009 08:27 AM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Stupid posting limit.

Here is the datasheet for the FET so you know which pin is which:

http://www.alldatasheet.com/datashee...AP40T03GI.html

mobaar 03-03-2009 08:44 AM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Thanks for all of your responses. Regarding which capacitors to get, would the HE series of Nichicon be appropriate? It's the only line I could find for every capacitor (I think the 50V only had PV). I don't know the first thing about ESR so any help would be appreciated.

I think I'll hold off on replacing the big-boy capacitor per your suggestions. It looks good, and although I had to cut through the thermal paste to get a look at the other side of the capacitor, everything looks A-OK so I'll hold off for now. I will still be sure to measure those other caps to make sure they fit. I have a digital caliper so I should be ok for that.

What would indicate a bad MOSFET? I want voltage drop one-way, but what if it's faulty? No closing of the circuit? no voltage drop?

Thanks again!

Collin

Scenic 03-03-2009 09:25 AM

Re: Issue with Westinghouse 19" LCD Monitor (large pics)
 
Quote:

Originally Posted by mobaar
What would indicate a bad MOSFET? I want voltage drop one-way, but what if it's faulty? No closing of the circuit? no voltage drop?

most of the time they'll short out if they fail.
(every pin -> 0 or almost 0 ohm)


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