Westinghouse L2046NV 2 seconds to black

[Mr Bill]

I got this monitor from the trash. 2 Caps failed so i recapped the entire board with panasonic fm caps (same valued). Turned the monitor back on and i still have the same symptoms. I did shine my flashlight on the screen and the picture is still there just no backlight.I've been trying to test the MOSFETS but i am not sure i am doing it correctly. If i put the leads on the the mosfet pins as per Retired caps's guide, i get a brief flash of a number then OL. I'm using a craftsman 82141 multimeter. I did check the 2 fuses on the inverter side of the power board and i am getting .3 ohms, so i am assuming they are ok. I checked the diodes on the board and they appear to be ok, (value one way and OL the other).

The MOSFET is 40T03GP
I've read in a few older posts that they do fail. If someone can chime in on the testing procedure. Or if i need a better multimeter to perform this test.

I am a little confused on the transformer check also. The guide says check pins 1-2 1-3 1-4.....Is this from top to bottom on either left or right side??

If anyone has any suggestions as to what to check or input on the mosfets i'm all ears.

Thanks

[jayoung]

Re: Westinghouse L2046NV 2 seconds to black

You said you still have the same symptoms - What are the symptoms?

[retiredcaps]

Re: Westinghouse L2046NV 2 seconds to black

I've been trying to test the MOSFETS but i am not sure i am doing it correctly. If i put the leads on the the mosfet pins as per Retired caps's guide, i get a brief flash of a number then OL. I'm using a craftsman 82141 multimeter.

Odd for a manual ranging multimeter to display "0L". Most manual multimeters display "1" on the left hand side to indicate out of range.

Anyway, it sounds like the mosfet is not shorted. However, it still could be bad. You can perform another test following

http://www.4qdtec.com/mostest.html

I did check the 2 fuses on the inverter side of the power board and i am getting .3 ohms, so i am assuming they are ok.

Please circle the 2 fuses. The flash on the picture makes it difficult to identify them. Also on this board, there may be a hidden fuse underneath the glue. If the PCB designator starts with a "F" that is a fuse.

The MOSFET is 40T03GP
Or if i need a better multimeter to perform this test.

Your multimeter is fine.

I am a little confused on the transformer check also. The guide says check pins 1-2 1-3 1-4.....Is this from top to bottom on either left or right side??

It doesn't matter how you number them because it tests every possible combination to identify which are the secondary pins. Your inverter transformer starts with 2874. If you look at

http://www.lcdparts.net/T.aspx

there are two part numbers with 2874. Both show that the outer corner pins are the secondary pins. So measure the resistance between S1 and S2. Do the same for S3 and S4. Report both numbers. An example,

http://www.lcdparts.net/TransformerD...ProductID=3359

[retiredcaps]

Re: Westinghouse L2046NV 2 seconds to black

You said you still have the same symptoms - What are the symptoms?

I'm assuming 2 seconds to black as per title. And he can see image with flashlight.

[alexanna]

Re: Westinghouse L2046NV 2 seconds to black

Just to make sure you checked the corect fuse for the inverter,it's F200 on the back side of the board.

[Mr Bill]

Re: Westinghouse L2046NV 2 seconds to black

Odd for a manual ranging multimeter to display "0L". Most manual multimeters display "1" on the left hand side to indicate out of range.]

Your right, i was typing faster than thinking

there are two part numbers with 2874. Both show that the outer corner pins are the secondary pins. So measure the resistance between S1 and S2. Do the same for S3 and S4. Report both numbers.

I measured s1-s2 and s3-s4, i'm getting a brief flash again (nowhere near 610) then "1". I also measured p1-p2 &p3-p4 for giggles and i got .3 ohm

As for the MOSFET i checked the 2 40T03GP, the one i get nothing, just 1. On the other i'm getting 733 between the source and gate. But when i put my finger between the leads it doesn't change.

Here is the pic of the 2 Fuses that i can find on the inverter side (F100, F101) I can zoom in on that particular area with the flash off if you would like.

Thanks

[Mr Bill]

Re: Westinghouse L2046NV 2 seconds to black

Just to make sure you checked the corect fuse for the inverter,it's F200 on the back side of the board.

I missed that one. Took a few minutes to find it. I'm getting .3 ohm

[retiredcaps]

Re: Westinghouse L2046NV 2 seconds to black

Just to make sure you checked the corect fuse for the inverter,it's F200 on the back side of the board.

Hmm, I knew something was funny about this board. I think you spotted that last year too!

[Mr Bill]

Re: Westinghouse L2046NV 2 seconds to black

i just checked the S1-S2 and S3-S4 on the inverter transformer with another meter (craftsman 82040 auto ranging meter) and i am getting 739 ohms on S1-S2 and 736 on S3-S4. 000.0 on P1-P2 & P3-P4.

[retiredcaps]

Re: Westinghouse L2046NV 2 seconds to black

I measured s1-s2 and s3-s4, i'm getting a brief flash again (nowhere near 610) then "1". I also measured p1-p2 &p3-p4 for giggles and i got .3 ohm

What did you have your multimeter set to? Did you set it to 2000 (two thousand) Ohms?

The primary winding rarely fails.

As for the MOSFET i checked the 2 40T03GP, the one i get nothing, just 1. On the other i'm getting 733 between the source and gate. But when i put my finger between the leads it doesn't change.

I have never tested mosfets using the other method so I can't tell you if the readings are right or not. In addition, if you tested the mosfets "in circuit", you may not get reliable readings.

There are still the ccfls and/or wiring along with the secondary inverter transformer that need to be checked.

[retiredcaps]

Re: Westinghouse L2046NV 2 seconds to black

i am getting 739 ohms on S1-S2 and 736 on S3-S4.

With manual range multimeters you have to get the range correct otherwise you get "1" or out of range. With those two readings, we can assume that the inverter transformer is good and move on.

[Mr Bill]

Re: Westinghouse L2046NV 2 seconds to black

I think the range was set to 200ohms on my meter. I retested the MOSfET and i'm getting 12.31, then i put my finger over the leads and it drops to 8. On the other it climbs to 40.12, then it drops to 2.2-2.3 I'm still using the auto range meter.

[retiredcaps]

Re: Westinghouse L2046NV 2 seconds to black

I suggest moving on to check the ccfls and its wiring. If you have a spare ccfl (doesn't matter what size), this test shouldn't take too long.

Luckily for you, alexanna is the king of ccfl wiring repair and can offer many suggestions.

See the following for examples of bad wiring or burnt out ccfls.

http://s807.photobucket.com/albums/y...klight%20lamp/

[alexanna]

Re: Westinghouse L2046NV 2 seconds to black

I missed that one. Took a few minutes to find it. I'm getting .3 ohm

Just to make sure I understand your problem, do you see a brief flash of the backlights?

[Mr Bill]

Re: Westinghouse L2046NV 2 seconds to black

yes, The monitor displays for 2 seconds then goes black. You can shine a flashlight on the screen and the images are there. how involved is it to remove the ccfl for inspections?

[alexanna]

Re: Westinghouse L2046NV 2 seconds to black

yes, The monitor displays for 2 seconds then goes black. You can shine a flashlight on the screen and the images are there. how involved is it to remove the ccfl for inspections?

Don't disassemble just yet.
Let's call the CCFL connectors “Top” and “bottom”
Unplug the top connectors; do the bottom CCFLs light briefly? Repeat with top plugged in and the bottom unplugged, do the top CCFLs light?And dose everything look the same top and bottom

[Mr Bill]

Re: Westinghouse L2046NV 2 seconds to black

There is 4 connectors for this montor. I plugged in the 2 going to the top and it lit up "no signal". I then unplugged the top and plugged in the 2 for the bottom and also lit up "no signal". As for the top and bottom it looked the same, brightness ect ect. It also os still doing the 2 seconds to black condition.

[alexanna]

Re: Westinghouse L2046NV 2 seconds to black

How easily would it be to come up of a pair of known good CCFLs?
These could be from another monitor/panel; there would be no need to disassemble anything.

[Mr Bill]

Re: Westinghouse L2046NV 2 seconds to black

How easily would it be to come up of a pair of known good CCFLs?
These could be from another monitor/panel; there would be no need to disassemble anything.

I do have an I-inc 19" monitor i bought back in 2007. It still works. I got a 32" tv i'm using as my computer monitor now. What would i need to do?

[alexanna]

Re: Westinghouse L2046NV 2 seconds to black

Before we disassemble anything there are some mor things we can check.
I am going to attach a schematic of the DCA19m-005 monitor/inverter.
there are some pins on the back light controller you could verify are good.
give me a moment to make some suggestions.We need to verify power/grounds and a back light on signal.