Westinghouse lcm-19v1 sl 2 Seconds to Black

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Now that I have a cup of coffee,you are going to have to measure,the resistance as follows;-
Black lead to 'x',measure to every other pin.
Black lead to 'y', measure to every other pin.
Black lead to 'z', measure to every other pin.
Note down all the results and compare them, they should be very very close for every transformer,if not then you will have to investigate from there.

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Its not possible to identify the secondarys from the photos unfortunately,ALSO where do your lamps plug into ??there seems to be no connection for them on the board.Measuring resistance the Black(negative lead) goes to common on the meter.I assume you are taking measurements with the board disconnected and no power on ??

[retiredcaps]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

1) This tutorial will help you understand some of the readings.

http://www.sparkfun.com/tutorials/202

2) My fellow Canadian has a 5 minute multimeter tutorial

http://www.youtube.com/watch?v=bF3OyQ3HwfU

3) Plus I have multimeter section starting with post #19

https://www.badcaps.net/forum/showthread.php?t=10419

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Yes, it turns out they are mosfets. U2, however, is 20 pins, and I can't find the datasheet for it. Should I test both channels, and how so? I can't seem to get a reading at all with my multimeter set to 200 ohms and my negative lead in com. The meter just says 1, as if nothing is connected.

Here's a schematic of the mosfet, TPC8401.


EDIT:
Rtech, did I test the right pins? Which pins are the secondary windings? Should my negative lead be in com or 10adc? I figured com, but I get a much higher reading when the lead is in 10adc.

[jetadm123]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

I believe the 8-pin devices,U1-U4?, are mosfets used to drive the inverter transformers. Check them for shorts. Look up the datasheet for these devices. With your meter set to 200 ohms, measure:

G--->D
G--->S
D--->S

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Here's a pic of both the top and bottom of the actual board. Sorry for the quality, I'll upload better photos soon.

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

0.4 ohms is not a secondary measurement,you are looking for something between 550-1200 ohms.A photo of the bottom of the Board would probably help.

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Ok. Here's a diagram of the transformers, with measurements of the secondary windings. I can also measure the primary windings if need be.

Xfmr 1:
x + y = 0.4 ohms
x + z = 0.4 ohms
y + z = 0.4 ohms

Xfmr 2:
x + y = 0.4 ohms
x + z = 0.4 ohms
y + z = 0.4 ohms

Xfmr 3:
x + y = 0.4 ohms
x + z = 0.4 ohms
y + z = 0.4 ohms

Xfmr 4:
x + y = 0.4 ohms
x + z = 0.4 ohms
y + z = 0.5 ohms

EDIT:
I should add that the back-light flickers on for about a second when I turn on the monitor, although only half of the bulbs turn on, and they don't look like they're on at full power.

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

You need to measure the resistance of the secondary winding on the inverter tfmrs,From the photo there is probably 2 pins at the top end(nearest the edge of the Board) of each tfmr.Measure each and advise.

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

yes. Underneath the board, there are two black plugs, spaced about 2 inches apart. Each plug has two slightly separate sections of four holes.

[jetadm123]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Where are the connectors for the ccfl's? Underneath the board?

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Right now, I don't have access to a camera, so It's a stock photo. I'll add actual pics sometime soon.

[retiredcaps]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Here's a picture of the top of the inverter board.

Is this a picture of your actual board or a stock photo?

[gregory121295]

So, I have a monitor that I've had for a couple months. I used it for about a week a month ago. It started out with the back-light working but the monitor needing to be hard reset until the back-light would stay on. After the back-light was on for a couple minutes, sometimes it would turn off later, sometimes it wouldn't.

I didn't think anything of it until one day, after about a week, it finally just turned off. I know it's the backlight, as the panel works just fine.

What the odd thing is, though, is that the only non surface mount capacitors on this board are on the control board, not the inverter board, and they're aluminum caps, not electrolytic.

Here's a picture of the top of the inverter board.